AD9981

High Performance 10-Bit Display Interface AD9981 FEATURES 10-bit analog-to-digital converter 95 MSPS maximum conversion rate 9% or less p-p PLL clock jitter at 95 MSPS Automated offset adjustment 2:1 input mux Power-down via dedicated pin or serial register 4:4:4, 4:2:2, and DDR output format modes Variable output drive strength Odd/even field detection External clock input Regenerated Hsync output Programmable output high impedance control Hsyncs per Vsyncs counter Pb-free package FUNCTIONAL BLOCK DIAGRAM 10 AUTO OFFSET AD9981 10 OUPUT DATA FORMATTER PR/REDIN1 PR/REDIN0 2:1 MUX CLAMP PGA 10 10-BIT ADC 10 REDOUT AUTO OFFSET Y/GREENIN1 Y/GREENIN0 2:1 MUX CLAMP PGA 10 10-BIT ADC 10 10 GREENOUT AUTO OFFSET PB/BLUEIN1 PB/BLUEIN0 2:1 MUX CLAMP PGA 10-BIT ADC 10 10 BLUEOUT HSYNC1 HSYNC2 2:1 MUX DATACK SYNC PROCESSING PLL SOGOUT O/E FIELD HSOUT VSOUT/A0 VSYNC1 VSYNC2 2:1 MUX APPLICATIONS Advanced TVs Plasma display panels LCDTV HDTV RGB graphics processing LCD monitors and projectors Scan converters SOGIN1 SOGIN2 EXTCLK/COAST CLAMP FILT 2:1 MUX POWER MANAGEMENT REFHI SCL SERIAL REGISTER REFLO 04739-001 SDA VOLTAGE REFS REFCM Figure 1. GENERAL DESCRIPTION The AD9981 is a complete, 10-bit, 95 MSPS, monolithic analog interface optimized for capturing YPbPr video and RGB graphics signals. Its 95 MSPS encode rate capability and fullpower analog bandwidth of 200 MHz supports all HDTV video modes and graphics resolutions up to XGA (1024 × 768 at 85 Hz). The AD9981 includes a 95 MHz triple ADC with an internal reference, a PLL, programmable gain, offset, and clamp controls. The user provides only 3.3 V and 1.8 V power supplies and an analog input. Three-state CMOS outputs may be powered from 1.8 V to 3.3 V. The AD9981’s on-chip PLL generates a sample clock from the three-level sync (for YPbPr video) or the horizontal sync (for RGB graphics). Sample clock output frequencies range from 10 MHz to 95 MHz. PLL clock jitter is 9% or less p-p typical at 95 MSPS. With internal Coast generation, the PLL maintains its output frequency in the absence of sync input. A 32-step sampling clock phase adjustment is provided. Output data, sync, and clock phase relationships are maintained. The auto-offset feature can be enabled to automatically restore the signal reference levels and to automatically calibrate out any offset differences between the three channels. The AD9981 also offers full sync processing for composite sync and sync-ongreen applications. A clamp signal is generated internally or may be provided by the user through the CLAMP input pin. Fabricated in an advanced CMOS process, the AD9981 is provided in a space-saving, 80-pin, Pb-free, LQFP surface mount plastic package. It is specified over the 0°C to +70°C temperature range. Rev. 0 Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.326.8703 © 2005 Analog Devices, Inc. All rights reserved. AD9981 TABLE OF CONTENTS Analog Interface Specifications ...................................................... 3 Absolute Maximum Ratings............................................................ 5 Explanation of Test Levels ........................................................... 5 ESD Caution .................................................................................. 5 Pin Configuration and Function Descriptions ............................. 6 Design Guide ................................................................................... 11 General Description ................................................................... 11 Digital Inputs .............................................................................. 11 Input Signal Handling ................................................................ 11 Hsync and Vsync Inputs ............................................................ 11 Serial Control Port ..................................................................... 11 Output Signal Handling............................................................. 11 Clamping ..................................................................................... 11 Gain and Offset Control ............................................................ 12 Timing Diagrams........................................................................ 20 Hsync Timing ............................................................................. 21 Coast Timing............................................................................... 21 Output Formatter ....................................................................... 21 Two-Wire Serial Register Map ...................................................... 23 Detailed 2-Wire Serial Control Register Descriptions .............. 29 Chip Identification ..................................................................... 29 PLL Divider Control .................................................................. 29 Clock Generator Control .......................................................... 29 Phase Adjust ................................................................................ 30 Input Gain ................................................................................... 30 Input Offset ................................................................................. 30 Hsync Controls ........................................................................... 31 Vsync Controls ........................................................................... 31 Coast and Clamp Controls........................................................ 32 SOG Control ............................................................................... 34 Input and Power Control........................................................... 34 Output Control ........................................................................... 35 Two-Wire Serial Control Port....................................................... 40 Data Transfer via Serial Interface ............................................. 40 PCB Layout Recommendations ............................................... 42 PLL ............................................................................................... 42 Outline Dimensions ....................................................................... 44 Ordering Guide .......................................................................... 44 REVISION HISTORY 1/05—Initial Version: Revision 0 Rev. 0 | Page 2 of 44 AD9981 ANALOG INTERFACE SPECIFICATIONS VD = 3.3 V, VDD = 3.3 V, PVD = 1.8 V, DAVDD = 1.8 V, ADC clock = maximum conversion rate , full temperature range = 0°C to 70°C. Table 1. Electrical Characteristics AD9981KSTZ-801 Parameter RESOLUTION Number of Bits LSB Size DC ACCURACY Differential Nonlinearity 80 MSPS Conversion Rate Differential Nonlinearity 95 MSPS Conversion Rate Integral Nonlinearity 80 MSPS Conversion Rate Integral Nonlinearity 95 MSPS Conversion Rate No Missing Codes ANALOG INPUT Input Voltage Range Minimum Maximum Gain Tempco Input Bias Current Input Full-Scale Matching Offset Adjustment Range SWITCHING PERFORMANCE Maximum Conversion Rate Minimum Conversion Rate Clock to Data Skew tSKEW tBUFF tSTAH tDHO tDAL tDAH tDSU tSTASU tSTOSU Maximum PLL Clock Rate Minimum PLL Clock Rate PLL Jitter Sampling Phase Tempco DIGITAL INPUTS3 Input Voltage, High (VIH) Input Voltage, Low (VIL) Input Current, High (IIH) Input Current, Low (IIL) Input Capacitance Temp Test Level Min Typ 10 0..098 Max Min AD9981KSTZ-952 Typ 10 0.098 Max Unit Bits % of full scale LSB LSB LSB LSB LSB 25°C Full 25°C Full 25°C Full 25°C Full 25°C I VI I VI I VI I VI I 0.3 0.4 1.0 1.8 ±1.4 ±1.4 ±3.75 ±5.0 Guaranteed 0.3 1.0 0.4 1.8 1.3 2.75 1.75 5.4 ±1.4 ±3.75 ±1.4 ±5.0 ±2.7 ±4.75 ±3.7 ±8.6 Guaranteed Full Full 25°C 25°C Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full Full 25°C Full Full Full Full Full Full 25°C VI VI V V V VI VI VI IV IV VI VI VI VI VI VI VI VI VI IV IV IV IV VI VI V V V 0.5 1.0 105 1 1 9 1.0 105 0.5 1 44 80 −0.5 4.7 4.0 0 4.7 4.0 250 4.7 4.0 80 750 15 2.5 1 44 95 1 1 10 V p-p V p-p ppm/°C µA µA % FS % FS MSPS MSPS ns µS µS µS µS µS nS µS µS MHz MHz ps p-p ps p-p ps/°C V V µA µA pF 10 +2 −0.5 4.7 4.0 0 4.7 4.0 250 4.7 4.0 95 980 15 2.5 10 +2 10 10 0.8 –82 82 2 –82 82 2 0.8 Rev. 0 | Page 3 of 44 AD9981 AD9981KSTZ-801 Parameter DIGITAL OUTPUTS Output Voltage, High (VOH) Output Voltage, Low (VOL) Duty Cycle, DATACK Output Coding POWER SUPPLY VD Supply Voltage VDD Supply Voltage PVD Supply Voltage DAVD Supply Voltage ID Supply Current (VD) IDD Supply Current (VDD)4 IPVD Supply Current (PVD) IDAVD Supply Current (DAVD) Total Power Dissipation Power-Down Supply Current Power-Down Dissipation DYNAMIC PERFORMANCE Analog Bandwidth, Full Power Crosstalk THERMAL CHARACTERISTICS θJC, Junction-to-Case Thermal Resistance θJA, Junction-to-Ambient Thermal Resistance Temp Full Full Full Test Level VI VI IV Min VDD − 0.2 0.2 50 Binary 3.13 1.7 1.7 1.7 3.3 3.3 1.8 1.8 233 42 11 10 953 18 55 200 60 16 35 3.47 3.47 1.9 1.9 3.13 1.7 1.7 1.7 50 Binary 3.3 3.3 1.8 1.8 205 49 8 12 993 18 55 200 60 16 35 3.47 3.47 1.9 1.9 Typ Max Min VDD − 0.2 0.1 AD9981KSTZ-952 Typ Max Unit V V % Full Full Full Full 25°C 25°C 25°C 25°C Full Full Full 25°C Full IV IV IV IV V V V V VI VI VI V V V V 1070 27 81 1114 28 88 V V V V mA mA mA mA mW mA mW MHz dBc °C/W °C/W 1 2 Output drive strength = 0 was used for all 80 MHz parameters. Output drive strength = 1 was used for all 95 MHz parameters. 3 Digital inputs are: HSYNC0, HSYNC1, VSYNC0, VSYNC1, SDA, SCL, EXTCLK, CLAMP, PWRDN, COAST 4 DATACK load = 10 pF, data load = 5 pF Rev. 0 | Page 4 of 44 AD9981 ABSOLUTE MAXIMUM RATINGS Table 2. Parameter VD VDD PVD DAVDD Analog Inputs REFHI REFCM REFLO Digital Inputs Digital Output Current Operating Temperature Storage Temperature Maximum Junction Temperature Rating 3.6 V 3.6 V 1.98 V 1.98 V VD to 0.0 V VD to 0.0 V VD to 0.0 V VD to 0.0 V 5 V to 0.0 V 20 mA −25°C to +85°C −65°C to +150°C 150°C Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions outside of those indicated in the operation sections of this specification is not implied. Exposure to absolute maximum ratings for extended periods may affect device reliability. EXPLANATION OF TEST LEVELS Test Level I. 100% production tested. II. 100% production tested at 25°C and sample tested at specified temperatures. III. Sample tested only. IV. Parameter is guaranteed by design and characterization testing. V. Parameter is a typical value only. VI. 100% production tested at 25°C; guaranteed by design and characterization testing. ESD CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although this product features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. Rev. 0 | Page 5 of 44 AD9981 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS EXTCLK/COAST VDD (3.3V) PVD (1.8V) PVD (1.8V) PVD (1.8V) BLUE BLUE BLUE 60 PIN 1 59 58 57 56 55 54 CCLAMP HSYNC0 HSYNC1 VSYNC0 VSYNC1 GND GND GND 80 79 78 77 76 75 74 73 72 71 70 69 68 67 66 65 64 63 62 61 VD (3.3V) BAIN0 GND BAIN1 VD (3.3V) GAIN0 GND SOGIN0 VD (3.3V) 1 2 3 4 5 6 7 8 9 GND SDA FILT SCL BLUE BLUE BLUE BLUE BLUE BLUE BLUE GND VDD (3.3V) GREEN GREEN GREEN GREEN GREEN GREEN GREEN GREEN GREEN GREEN DAVDD (1.8) 04739-002 AD9981 TOP VIEW (Not to Scale) 53 52 51 50 49 48 47 46 45 44 43 42 41 GAIN1 10 GND 11 SOGIN1 12 VD (3.3V) 13 RAIN0 14 GND 15 RAIN1 16 PWRDN 17 REFLO 18 REFCM 19 REFHI 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 O/E FIELD VDD (3.3V) VSOUT/A0 VDD (3.3V) SOGOUT RED RED RED RED RED RED RED RED RED RED GND GND HSOUT DATACK Figure 2. Top View (Pins Down) Table 3. Complete Pinout List Pin Type Inputs Mnemonic RAIN0 RAIN1 GAIN0 GAIN1 BAIN0 BAIN1 HSYNC0 HSYNC1 VSYNC0 VSYNC1 SOGIN0 SOGIN1 EXTCK CLAMP COAST PWRDN RED [9:0] GREEN [9:0] BLUE [9:0] DATACK Function Channel 0 Analog Input for Converter R Channel 1 Analog Input for Converter R Channel 0 Analog Input for Converter G Channel 1 Analog Input for Converter G Channel 0 Analog Input for Converter B Channel 1 Analog Input for Converter B Horizontal Sync Input for Channel 0 Horizontal Sync Input for Channel 1 Vertical Sync Input for Channel 0 Vertical Sync Input for Channel 1 Input for Sync-on-Green Channel 0 Input for Sync-on-Green Channel 1 External Clock Input External Clamp Input Signal External PLL Coast Signal Input Power-Down Control Outputs of Converter R, Bit 9 is the MSB Outputs of Converter G, Bit 9 is the MSB Outputs of Converter B, Bit 9 is the MSB Data Output Clock Rev. 0 | Page 6 of 44 GND Outputs Value 0.0 V to 1.0 V 0.0 V to 1.0 V 0.0 V to 1.0 V 0.0 V to 1.0 V 0.0 V to 1.0 V 0.0 V to 1.0 V 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 0.0 V to 1.0 V 0.0 V to 1.0 V 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS Pin No. 14 16 6 10 2 4 70 68 71 69 8 12 721 73 72 17 28 to 37 42 to 51 54 to 63 25 1 AD9981 Pin Type Mnemonic HSOUT VSOUT SOGOUT O/E FIELD FILT REFLO REFCM REFHI VD VDD PVD DAVDD GND Function Hsync Output Clock (Phase-Aligned with DATACK) Vsync Output Clock Sync-on-Green Slicer Output Odd/Even Field Output Connection for External Filter Components for Internal PLL Connection for External Capacitor for Input Amplifier Connection for External Capacitor for Input Amplifier Connection for External Capacitor for Input Amplifier Analog Power Supply Output Power Supply PLL Power Supply Digital Logic Power Supply Ground Value 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 3.3V CMOS Pin No. 23 222 24 21 78 18 19 20 1, 5, 9, 13 26, 38, 52, 64 74, 76, 79 41 3, 7, 11, 15, 27, 39, 40, 53, 65, 75, 77, 80 66 67 22 2 References Power Supply 3.3 V 1.8 V or 3.3 V 1.8 V 1.8 V 0V Control SDA SCL A0 Serial Port Data I/O Serial Port Data Clock (100 kHz maximum) Serial Port Address Input 3.3 V CMOS 3.3 V CMOS 3.3 V CMOS 1 2 EXTCLK and COAST share the same pin. VSOUT and A0 share the same pin. Rev. 0 | Page 7 of 44 AD9981 Table 4. Pin Function Descriptions Pin INPUTS RAIN0 GAIN0 BAIN0 RAIN1 GAIN1 BAIN1 Description Analog Input for the Red Channel 0. Analog Input for the Green Channel 0. Analog Input for the Blue Channel 0. Analog Input for the Red Channel 1. Analog Input for the Green Channel 1. Analog Input for the Blue Channel 1. High impedance inputs that accept the red, green, and blue channel graphics signals, respectively. The three channels are identical and can be used for any colors, but colors are assigned for convenient reference. They accommodate input signals ranging from 0.5 V to 1.0 V full scale. Signals should be ac-coupled to these pins to support clamp operation. Horizontal Sync Input Channel 0. Horizontal Sync Input Channel 1. These inputs receive a logic signal that establishes the horizontal timing reference and provides the frequency reference for pixel clock generation. The logic sense of this pin can be automatically determined by the chip or manually controlled by Serial Register 0x12, Bits [5:4] (Hsync polarity). Only the leading edge of Hsync is used by the PLL; the trailing edge is used in clamp timing. When Hsync polarity = 0, the falling edge of Hsync is used. When Hsync Polarity = 1, the rising edge is active. The input includes a Schmitt trigger for noise immunity. Vertical Sync Input Channel 0. Vertical Sync Input Channel 1. These are the inputs for vertical sync and provide timing information for generation of the field (odd/even) and internal Coast generation. The logic sense of this pin can be automatically determined by the chip or manually controlled by Serial Register 0x14, Bits [5:4] (Vsync polarity). Sync-on-Green Input Channel 0. Sync-on-Green Input Channel 1. These inputs are provided to assist with processing signals with embedded sync, typically on the green channel. The pin is connected to a high speed comparator with an internally generated threshold. The threshold level can be programmed in 8 mV steps to any voltage between 8 mV and 256 mV above the negative peak of the input signal. The default voltage threshold is 128 mV. When connected to an ac-coupled graphics signal with embedded sync, it produces a noninverting digital output on SOGOUT. This is usually a composite sync signal, containing both vertical and horizontal sync information that must be separated before passing the horizontal sync signal for Hsync processing. When not used, this input should be left unconnected. For more details on this function and how it should be configured, refer to the Sync-on-Green section. External Clamp Input (Optional). This logic input may be used to define the time during which the input signal is clamped to ground or midscale. It should be exercised when the reference dc level is known to be present on the analog input channels, typically during the back porch of the graphics signal. The CLAMP pin is enabled by setting the control bit clamp function to 1, (Register 0x18, Bit 4; default is 0). When disabled, this pin is ignored and the clamp timing is determined internally by counting a delay and duration from the trailing edge of the Hsync input. The logic sense of this pin can be automatically determined by the chip or controlled by clamp polarity Register 0x1B, Bits [7:6]. When not used, this pin may be left unconnected (there is an internal pull-down resistor) and the clamp function programmed to 0. Coast Input to Clock Generator (Optional). This input may be used to cause the pixel clock generator to stop synchronizing with Hsync and continue producing a clock at its current frequency and phase. This is useful when processing signals from sources that fail to produce Hsync pulses during the vertical interval. The Coast signal is generally not required for PC-generated signals. The logic sense of this pin can be determined automatically or controlled by Coast polarity (Register 0x18, Bits [7:6]). When not used and EXTCLK is not used, this pin may be grounded and Coast polarity programmed to 1. Input Coast polarity defaults to1 at power-up. This pin is shared with the EXTCLK function, which does not affect Coast functionality. For more details on EXTCLK, see the description in this section. External Clock. This allows the insertion of an external clock source rather than the internally generated, PLL locked clock. EXTCLK is enabled by programming Register 0x03, Bit 2 to 1. This pin is shared with the Coast function, which does not affect EXTCLK functionality. For more details on Coast, see the above description in this section. Power-Down Control This pin can be used along with Register 0x1E, Bit 3 for manual power-down control. If manual power-down control is selected (Register 0x1E, Bit 4) and this pin is not used, it is recommended to set the pin polarity (Register 0x1E, Bit 2) to active high and hardwire this pin to ground with a 10 kΩ resistor. HSYNC0 HSYNC1 VSYNC0 VSYNC1 SOGIN0 SOGIN1 CLAMP EXTCLK/COAST EXTCLK/COAST PWRDN Rev. 0 | Page 8 of 44 AD9981 Pin REFLO REFCM REFHI FILT Description Input Amplifier Reference. REFLO and REFHI are connected together through a 10 µF capacitor; REFCM is connected through a 10 µF capacitor to ground. These are used for stability in the input PGA (programmable gain amplifier) circuitry. See Figure 4. External Filter Connection. For proper operation, the pixel clock generator PLL requires an external filter. Connect the filter shown in Figure 5to this pin. For optimal performance, minimize noise and parasitics on this node. For more information, see the PCB Layout Recommendations section. Horizontal Sync Output. A reconstructed and phase-aligned version of the Hsync input. Both the polarity and duration of this output can be programmed via serial bus registers. By maintaining alignment with DATACK and Data Output, data timing with respect to Hsync can always be determined. Vertical Sync Output. Pin shared with A0, serial port address. This can be either a separated Vsync from a composite signal or a direct pass through of the Vsync signal. The polarity of this output can be controlled via a serial bus bit. The placement and duration in all modes can be set by the graphics transmitter or the duration can be set by Register 0x14 and Register 0x15. This pin is shared with the A0 function, which does not affect Vsync Output functionality. For more details on A0, see the description in the Serial Control Port section. Sync-On-Green Slicer Output. This pin outputs one of four possible signals (controlled by Register 0x1D, Bits [1:0]): raw SOG, raw Hsync, regenerated Hsync from the filter, or the filtered Hsync. See the sync processing block diagram (see Figure 8) to view how this pin is connected. Other than slicing off SOG, the output from this pin gets no other additional processing on the AD9981. Vsync separation is performed via the sync separator. Odd/Even Field Bit for Interlaced Video. This output will identify whether the current field (in an interlaced signal) is odd or even. Serial Port Data I/O. Serial Port Data Clock. Serial Port Address Input 0. Pin shared with VSOUT. This pin selects the LSB of the serial port device address, allowing two Analog Devices parts to be on the same serial bus. A high impedance external pull-up resistor enables this pin to be read at power-up as 1, or a high impedance, external pull-down resistor enables this pin to be read at power-up as a 0 and not interfere with the VSOUT functionality. For more details on VSOUT, see the Data Outputs section in this table. Data Output, Red Channel. Data Output, Green Channel. Data Output, Blue Channel. The main data outputs. Bit 9 is the MSB. The delay from pixel sampling time to output is fixed. When the sampling time is changed by adjusting the phase register, the output timing is shifted as well. The DATACK and HSOUT outputs are also moved, so the timing relationship among the signals is maintained. OUTPUTS HSOUT VSOUT/A0 SOGOUT O/E FIELD SERIAL PORT SDA SCL VSOUT/A0 DATA OUTPUTS RED [9:0] GREEN [9:0] BLUE [9:0] DATA CLOCK OUTPUT DATACK Data Clock Output. This is the main clock output signal used to strobe the output data and HSOUT into external logic. Four possible output clocks can be selected with Register 0x20, Bits [7:6]. Three of these are related to the pixel clock (pixel clock, 90° phase-shifted pixel clock and 2× frequency pixel clock). They are produced either by the internal PLL clock generator or EXTCLK and are synchronous with the pixel sampling clock. The fourth option for the data clock output is an internally generated 40 MHz clock. The sampling time of the internal pixel clock can be changed by adjusting the phase register (Register 0x04). When this is changed, the pixel related DATACK timing is also shifted. The Data, DATACK, and HSOUT outputs are all moved so that the timing relationship among the signals is maintained. Rev. 0 | Page 9 of 44 AD9981 Pin POWER SUPPLY VD (3.3 V) VDD (1.8 V–3.3 V) Description Main Power Supply. These pins supply power to the main elements of the circuit. They should be as quiet and filtered as possible. Digital Output Power Supply. A large number of output pins (up to 35) switching at high speed (up to 95 MHz) generate a lot of power supply transients (noise). These supply pins are identified separately from the VD pins, so special care can be taken to minimize output noise transferred into the sensitive analog circuitry. If the AD9981 is interfacing with lower voltage logic, VDD may be connected to a lower supply voltage (as low as 1.8 V) for compatibility. Clock Generator Power Supply. The most sensitive portion of the AD9981 is the clock generation circuitry. These pins provide power to the clock PLL and help the user design for optimal performance. The designer should provide quiet, noise-free power to these pins. Digital Input Power Supply. This supplies power to the digital logic. Ground. The ground return for all circuitry on-chip. It is recommended that the AD9981 be assembled on a single solid ground plane, with careful attention to ground current paths. PVD (1.8 V) DAVDD (1.8 V) GND Rev. 0 | Page 10 of 44 AD9981 DESIGN GUIDE GENERAL DESCRIPTION The AD9981 is a fully integrated solution for capturing analog RGB or YPbPr signals and digitizing them for display on advanced TVs, flat panel monitors, projectors, and other types of digital displays. Implemented in a high-performance CMOS process, the interface can capture signals with pixel rates of up to 95 MHz. The AD9981 includes all necessar y input buffering, signal DC restoration (clamping), offset and gain (brightness and contrast) adjustment, pixel clock generation, sampling phase control, and output data formatting. All controls are programmable via a two-wire serial interface (I2C®). Full integration of these sensitive analog functions makes system design straightfor ward and less sensitive to the physical and electrical environment. With a typical power dissipation of less than 900 mW and an operating temperature range of 0°C to 70°C, the device requires no special environmental considerations. slightly and providing a high quality signal over a wider range of conditions. Using a Fair-Rite #2508051217Z0-High Speed, Signal Chip Bead Inductor in the circuit shown in Figure 3 gives good results in most applications. RGB INPUT 75Ω 47nF RAIN GAIN BAIN Figure 3. Analog Input Interface Circuit HSYNC AND VSYNC INPUTS The interface also accepts Hsync and Vsync signals, which are used to generate the pixel clock, clamp timing, Coast and field information. These can be either a sync signal directly from the graphics source, or a preprocessed TTL or CMOS level signal. The Hsync input includes a Schmitt trigger buffer for immunity to noise and signals with long rise times. In typical PC-based graphic systems, the sync signals are simply TTL-level drivers feeding unshielded wires in the monitor cable. As such, no termination is required. DIGITAL INPUTS All digital inputs on the AD9981 operate to 3.3 V CMOS levels. The following digital inputs are 5 V tolerant (Applying 5 V to them will not cause any damage.): HSYNC0, HSYNC1, VSYNC0, VSYNC1, SOGIN0, SOGIN1, SDA, SCL and CLAMP. SERIAL CONTROL PORT The serial control port is designed for 3.3 V logic; however, it is tolerant of 5 V logic signals. INPUT SIGNAL HANDLING The AD9981 has six high-impedance analog input pins for the red, green, and blue channels. They accommodate signals ranging from 0.5 V to 1.0 V p-p. Signals are typically brought onto the interface board with a DVI-I connector, a 15-pin D connector, or RCA connectors. The AD9981 should be located as close as possible to the input connector. Signals should be routed using matched-impedance traces (normally 75 Ω) to the IC input pins. At the input pins the signal should be resistively terminated (75 Ω to the signal ground return) and capacitively coupled to the AD9981 inputs through 47 nF capacitors. These capacitors form part of the DC restoration circuit. In an ideal world of perfectly matched impedances, the best performance can be obtained with the widest possible signal bandwidth. The wide bandwidth inputs of the AD9981 (200 MHz) can continuously track the input signal as it moves from one pixel level to the next and can digitize the pixel during a long, flat pixel time. In many systems, however, there are mismatches, reflections, and noise, which can result in excessive ringing and distortion of the input waveform. This makes it more difficult to establish a sampling phase that provides good image quality. It has been shown that a small inductor in series with the input is effective in rolling off the input bandwidth OUTPUT SIGNAL HANDLING The digital outputs are designed to operate from 1.8 V to 3.3 V (VDD). CLAMPING RGB Clamping To properly digitize the incoming signal, the dc offset of the input must be adjusted to fit the range of the on-board ADCs. Most graphics systems produce RGB signals with black at ground and white at approximately 0.75 V. However, if sync signals are embedded in the graphics, the sync tip is often at ground and black is at 300 mV; then white is at approximately 1.0 V. Some common RGB line amplifier boxes use emitterfollower buffers to split signals and increase drive capability. This introduces a 700 mV dc offset to the signal, which must be removed for proper capture by the AD9981. The key to clamping is to identify a portion (time) of the signal when the graphic system is known to be producing black. An offset is then introduced that results in the ADC producing a black output (Code 0x00) when the known black input is present. The offset then remains in place when other signal levels are processed, and the entire signal is shifted to eliminate offset errors. Rev. 0 | Page 11 of 44 04739-003 AD9981 In most PC graphics systems, black is transmitted between active video lines. With CRT displays, when the electron beam has completed writing a horizontal line on the screen (at the right side), the beam is deflected quickly to the left side of the screen (called horizontal retrace) and a black signal is provided to prevent the beam from disturbing the image. In systems with embedded sync, a blacker-than-black signal (Hsync) is produced briefly to signal the CRT that it is time to begin a retrace. Because the input is not at black level at this time, it is important to avoid clamping during Hsync. Fortunately, there is virtually always a period following Hsync, called the ‘back porch’, where a good black reference is provided. This is the time when clamping should be done. The clamp timing can be established by simply exercising the CLAMP pin at the appropriate time with clamp source (Register 0x18, Bit 4) = 1. The polarity of this signal is set by the clamp polarity bit (Register 0x1B, Bits [7:6]). A simpler method of clamp timing employs the AD9981 internal clamp timing generator. The clamp placement register (Register 0x19) is programmed with the number of pixel periods that should pass after the trailing edge of Hsync before clamping starts. A second register, clamp duration, (Register 0x1A) sets the duration of the clamp. These are both 8-bit values, providing considerable flexibility in clamp generation. The clamp timing is referenced to the trailing edge of Hsync because, though Hsync duration can vary widely, the back porch (black reference) always follows Hsync. A good starting point for establishing clamping is to set the clamp placement to 0x04 (providing 4 pixel periods for the graphics signal to stabilize after sync) and set the clamp duration to 0x28 (giving the clamp 40 pixel periods to reestablish the black reference). Clamping is accomplished by placing an appropriate charge on the external input coupling capacitor. The value of this capacitor affects the performance of the clamp. If it is too small, there will be a significant amplitude change during a horizontal line time (between clamping intervals). If the capacitor is too large, then it will take excessively long for the clamp to recover from a large change in incoming signal offset. The recommended value (47 nF) results in recovering from a step error of 100 mV to within 1 LSB in 30 lines with a clamp duration of 20 pixel periods on a 85 Hz XGA signal. Clamping to midscale rather than ground can be accomplished by setting the clamp select bits in the serial bus register. Each of the three converters has its own selection bit so that they can be independently clamped to either midscale or ground. These bits are located in Register 0x18, Bits [3:1]. The midscale reference voltage is internally generated for each converter. GAIN AND OFFSET CONTROL The AD9981 contains three programmable gain amplifiers (PGAs), one for each of the three analog inputs. The range of the PGA is sufficient to accommodate input signals with inputs ranging from 0.5 V to 1.0 V full scale. The gain is set in three 9-bit registers (red gain [0x05, 0x06], green gain [0x07, 0x08], blue gain [0x09, 0x0A]). For each of these registers, a gain setting of 0 corresponds to the highest gain, while a gain setting of 511 corresponds to the lowest gain. Note that increasing the gain setting results in an image with less contrast. The offset control shifts the analog input, resulting in a change in brightness. Three 11-bit registers (red offset [0x0B, 0x0C], green offset [0x0D, 0x0E], blue offset [0x0F, 0x10]) provide independent settings for each channel. Note that the function of the offset register depends on whether auto-offset is enabled (Register 0x1B, Bit 5). If manual offset is used, nine bits of the offset registers (for the red channel Register 0x0B, Bits [6:0] plus Register 0x0C, Bits [7:6]) control the absolute offset added to the channel. The offset control provides ±255 LSBs of adjustment range, with one LSB of offset corresponding to one LSB of output code. Automatic Offset In addition to the manual offset adjustment mode, the AD9981 also includes circuitry to automatically calibrate the offset for each channel. By monitoring the output of each ADC during the back porch of the input signals, the AD9981 can self-adjust to eliminate any offset errors in its own ADC channels and any offset errors present on the incoming graphics or video signals. To activate the auto-offset mode, set Register 0x1B, Bit 5 to 1. Next, the target code registers (0x0B through 0x10) must be programmed. The values programmed into the target code registers should be the output code desired from the AD9981 during the back porch reference time. For example, for RGB signals, all three registers would normally be programmed to Code 1, while for YPbPr signals the green (Y) channel is normally set to Code 1 and the blue and red channels (Pb and Pr) are set to 512. The target code registers have 11 bits per channel and are in twos complement format. This allows any value between –1024 and +1023 to be programmed. Although any value in this range can be programmed, the AD9981’s offset range may not be able to reach every value. Intended target code values range from (but are not limited to) –160 to –1 and +1 to +160 when ground clamping, and +350 to +670 when midscale clamping. Note that a target code of 0 is not valid. YPbPr Clamping YPbPr graphic signals are slightly different from RGB signals in that the dc reference level (black level in RGB signals) of color difference signals is at the midpoint of the video signal rather than at the bottom. The three inputs are composed of luminance (Y) and color difference (Pb and Pr) signals. For color difference signals it is necessary to clamp to the midscale range of the ADC range (512) rather than to the bottom of the ADC range (0), while the Y channel is clamped to ground. Rev. 0 | Page 12 of 44 AD9981 Negative target codes are included in order to duplicate a feature that is present with manual offset adjustment. The benefit that is being mimicked is the ability to easily adjust brightness on a display. By setting the target code to a value that does not correspond to the ideal ADC range, the end result is an image that is either brighter or darker. A target code higher than ideal results in a brighter image, while a target code lower than ideal results in a darker image. The ability to program a target code gives a large degree of freedom and flexibility. While in most cases all channels are set to either 1 or 512, the flexibility to select other values allows the possibility of inserting intentional skews between channels. It also allows the ADC range to be skewed so that voltages outside of the normal range can be digitized. For example, setting the target code to 40 allows the sync tip, which is normally below black level, to be digitized and evaluated. The internal logic for the auto-offset circuit requires 16 data clock cycles to perform its function. This operation is executed immediately after the clamping pulse. Therefore, it is important to end the clamping pulse signal at least 16 data clock cycles before active video. This is true whether using the AD9981’s internal clamp circuit or an external clamp signal. The autooffset function can be programmed to run continuously or on a one-time basis (see auto-offset hold, Register 0x2C, Bit 4). In continuous mode, the update frequency can be programmed (Register 0x1B, Bits [4:3]). Continuous operation with updates ever y 64 Hsyncs is recommended. A guideline for basic auto-offset operation is shown in Table 5 and Table 6. Table 5. RGB Auto-Offset Register Settings Register 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x18, Bits [3:1] 0x1B, Bit [5:3] Value 0x00 0x80 0x00 0x80 0x00 0x80 000 110 Comments Sets red target to 4 Must be written Sets green target to 4 Must be written Sets blue target to 4 Must be written Sets red, green, and blue channels to ground clamp Selects update rate and enables auto-offset. Sync-on-Green The sync-on-green input operates in two steps. First, it sets a baseline clamp level off of the incoming video signal with a negative peak detector. Second, it sets the sync trigger level to a programmable (Register 0x1D, Bits [7:3]) level (typically 128 mV) above the negative peak. The sync-on-green input must be ac-coupled to the green analog input through its own capacitor. The value of the capacitor must be 1 nF ±20%. If sync-on-green is not used, this connection is not required. The sync-on-green signal always has negative polarity. 47nF RAIN 47nF BAIN 47nF GAIN SOG 04739-004 1nF Figure 4. Typical Input Configuration Reference Bypassing REFLO and REFHI are connected to each other by a 10 µF capacitor. REFCM is connected to ground by a 10 µF capacitor. These references are used by the input PGA circuitr y. REFHI 10µF REFLO 10µF REFCM 04739-014 Figure 5. Input Amplifier Reference Capacitors Clock Generation A PLL is used to generate the pixel clock. The Hsync input provides a reference frequency to the PLL. A voltagecontrolled oscillator (VCO) generates a much higher pixel clock frequency. The pixel clock is divided by the PLL divide value (Register 0x01 and Register 0x02) and phase-compared with the Hsync input. Any error is used to shift the VCO frequency and maintain lock between the two signals. The stability of this clock is a ver y important element in providing the clearest and most stable image. During each pixel time, there is a period when the signal is slewing from the old pixel amplitude and settling at its new value. Then there is a time when the input voltage is stable, before the signal must slew to a new value (see Figure 6). The ratio of the slewing time to the stable time is a function of the bandwidth of the graphics DAC and the bandwidth of the transmission system (cable and termination). It is also a function of the overall pixel rate. Clearly, if the dynamic characteristics of the system remain fixed, then the slewing and settling time is likewise fixed. This time must be subtracted from the total pixel period, leaving the stable period. At higher pixel frequencies, the total cycle time is shorter and the stable pixel time also becomes shorter. Table 6. PbPr Auto-Offset Register Settings Register 0x0B 0x0C 0x0D 0x0E 0x0F 0x10 0x18 Bits [3:1] 0x1B, Bit [5:3] Value 0x40 0x00 0x00 0x80 0x40 0x00 101 110 Comments Sets Pr (red) target to 512 Must be written Sets Y (green) target to 4 Must be written Sets Pb (blue) target to 512 Must be written Sets Pb, Pr to midscale clamp and Y to ground clamp Selects update rate and enables auto-offset. Rev. 0 | Page 13 of 44 AD9981 PIXEL CLOCK INVALID SAMPLE TIMES range register sets this operating range. The frequency ranges for the four regions are shown in Table 7. Table 7. VCO Frequency Ranges PV1 0 0 1 1 PV0 0 1 0 1 Pixel Clock Range (MHz) 10–21 21–42 42–84 84-95 KVCO Gain (MHz/V) 150 150 150 150 Figure 6. Pixel Sampling Times 04739-005 3. Any jitter in the clock reduces the precision with which the sampling time can be determined and must also be subtracted from the stable pixel time. Considerable care has been taken in the design of the AD9981’s clock generation circuit to minimize jitter. The clock jitter of the AD9981 is 9% or less of the total pixel time in all operating modes, making the reduction in the valid sampling time due to jitter negligible. The PLL characteristics are determined by the loop filter design, the PLL charge pump current, and the VCO range setting. The loop filter design is illustrated in Figure 7. Recommended settings of the VCO range and charge pump current for VESA standard display modes are listed in Table 9. CP 8nF RZ 1.5kΩ 04739-006 The 3-Bit Charge Pump Current Register. This register varies the current that drives the low-pass loop filter. The possible current values are listed in Table 8. Table 8. Charge Pump Current/Control Bits Ip2 0 0 0 0 1 1 1 1 Ip1 0 0 1 1 0 0 1 1 Ip0 0 1 0 1 0 1 0 1 Current (µA) 50 100 150 250 350 500 750 1500 CZ 80nF PVD 4. FILT Figure 7. PLL Loop Filter Detail Four programmable registers are provided to optimize the performance of the PLL. These registers are 1. The 12-Bit Divisor Register. The input Hsync frequencies can accommodate any Hsync as long as the product of the Hsync and the PLL divisor falls within the operating range of the VCO. The PLL multiplies the frequency of the Hsync signal, producing pixel clock frequencies in the range of 10 MHz to 95 MHz. The divisor register controls the exact multiplication factor. This register may be set to any value between 2 and 4095 as long as the output frequency is within range. The 2-Bit VCO Range Register. To improve the noise performance of the AD9981, the VCO operating frequency range is divided into four overlapping regions. The VCO 2. The 5-Bit Phase Adjust Register. The phase of the generated sampling clock may be shifted to locate an optimum sampling point within a clock cycle. The phase adjust register provides 32 phase-shift steps of 11.25° each. The Hsync signal with an identical phase shift is available through the HSOUT pin. Phase adjust is still available if an external pixel clock is used. The COAST pin or the internal Coast is used to allow the PLL to continue to run at the same frequency in the absence of the incoming Hsync signal or during disturbances in Hsync (such as from equalization pulses). This may be used during the vertical sync period or at any other time that the Hsync signal is unavailable. The polarity of the Coast signal may be set through the Coast polarity register (Register 0x18, Bits [6:5]). Also, the polarity of the Hsync signal may be set through the Hsync polarity register (Register 0x12, Bits [5:4]). For both Hsync and Coast, a value of 1 is active high. The internal Coast function is driven off the Vsync signal, which is typically a time when Hsync signals may be disrupted with extra equalization pulses. Rev. 0 | Page 14 of 44 AD9981 Table 9. Recommended VCO Range and Charge Pump and Current Settings for Standard Display Formats Refresh Rate Horizontal Frequency Pixel Rate PLL (kHz) (MHz) Divider Standard Resolution (Hz) VGA 640 × 480 60 72 75 85 56 60 72 75 85 60 70 75 80 85 30 60 30 60 60 30 60 31.500 37.700 37.500 43.300 35.100 37.900 48.100 46.900 53.700 48.400 56.500 60.000 64.000 68.300 15.750 31.470 15.625 31.250 45.000 33.750 33.750 25.175 31.500 31.500 36.000 36.000 40.000 50.000 49.500 56.250 65.000 75.000 78.750 85.500 94.500 13.510 27.000 13.500 27.000 74.250 74.250 74.250 800 832 840 832 1024 1056 1040 1056 1048 1344 1328 1312 1336 1376 858 858 864 864 1650 2200 2200 VCORNGE 01 01 01 01 01 01 10 10 10 10 10 10 11 11 00 01 00 01 10 10 10 Current 100 100 100 101 101 100 100 100 100 101 110 110 100 100 100 100 100 100 101 101 101 SVGA 800 × 600 XGA 1024 × 768 TV 480i 480p 576i 576p 720p 1035i 1080i Rev. 0 | Page 15 of 44 AD9981 CHANNEL SELECT CHANNEL MUX Preliminary Technical Data HSYNC SELECT HSYNC0 ACTIVITY DETECT HSYNC1 ACTIVITY DETECT SOGIN0 ACTIVITY DETECT SOGIN1 ACTIVITY DETECT POLARITY DETECT POLARITY DETECT HSYNC MUX EQ PULSE FILTER FILTERED, RECONSTRUCTED HSYNC CHANNEL MUX SOGOUT MUX SYNC SLICER SET POLARITY SOGOUT CHANNEL MUX VSYNC0 ACTIVITY DETECT VSYNC1 ACTIVITY DETECT POLARITY DETECT POLARITY DETECT SYNC PROCESSOR SET POLARITY VSYNC VSYNCOUT HSYNC/VSYNC HSYNC COAST COAST MUX COAST H/V COUNT R26, R27 SET POLARITY PLL CLOCK GENERATOR SET POLARITY VSYNCOUT DATACK 04739-013 AD9981 Figure 8. Sync Processing Block Diagram Sync Processing The inputs of the sync processing section of the AD9981 are combinations of digital Hsyncs and Vsyncs, analog sync-ongreen, or sync-on-Y signals, and an optional external Coast signal. From these signals it generates a precise, jitter-free (9% or less at 95 MHz) clock from its PLL; an odd-/even-field signal; Hsync and Vsync out signals; a count of Hsyncs per Vsync; and a programmable SOG output. The main sync processing blocks are the sync slicer, sync separator, Hsync filter, Hsync regenerator, Vsync filter, and Coast generator. The sync slicer extracts the sync signal from the green graphics or luminance video signal that is connected to the SOGIN input and outputs a digital composite sync. The sync separator’s task is to extract Vsync from the composite sync signal, which can come from either the sync slicer or the Hsync input. The Hsync filter is used to eliminate any extraneous pulses from the Hsync or SOGIN inputs, outputting a clean, low-jitter signal that is appropriate for mode detection and clock generation. The Hsync regenerator is used to recreate a clean, although not low jitter, Hsync signal that can be used for mode detection and counting Hsyncs per Vsync. The Vsync filter is used to eliminate spurious Vsyncs, maintain a stable timing relationship between the Vsync and Hsync output signals, and generate the odd/even field output. The Coast generator creates a robust Coast signal that allows the PLL to maintain its frequency in the absence of Hsync pulses. Sync Slicer The purpose of the sync slicer is to extract the sync signal from the green graphics or luminance video signal that is connected to the SOGIN input. The sync signal is extracted in a two step process. First, the SOG input is clamped to its negative peak, (typically 0.3 V below the black level). Next, the signal goes to a comparator with a variable trigger level (set by Register 0x1D, Bits [7:3]), but nominally 0.128 V above the clamped level. The sync slicer output is a digital composite sync signal containing both Hsync and Vsync information (see Figure 9). Rev. 0 | Page 16 of 44 AD9981 NEGATIVE PULSE WIDTH = 40 SAMPLE CLOCKS 700mV MAXIMUM SOG INPUT –300mV 0mV –300mV SOGOUT OUTPUT CONNECTED TO HSYNCIN VSYNCOUT FROM SYNC SEPARATOR Figure 9. Sync Slicer and Sync Separator Output Sync Separator As part of sync processing, the sync separator’s task is to extract Vsync from the composite sync signal. It works on the idea that the Vsync signal stays active for a much longer time than the Hsync signal. By using a digital low-pass filter and a digital comparator, it rejects pulses with small durations (such as Hsyncs and equalization pulses) and only passes pulses with large durations, such as Vsync (see Figure 9). The threshold of the digital comparator is programmable for maximum flexibility. To program the threshold duration, write a value (N) to Register 0x11. The resulting pulse width is N × 200 ns. So, if N = 5 the digital comparator threshold is 1 µs. Any pulse less than 1 µs is rejected, while any pulse greater than 1 µs passes through. There are two things to keep in mind when using the sync separator. First, the resulting clean Vsync output is delayed from the original Vsync by a duration equal to the digital comparator threshold (N × 200 ns). Second, there is some variability to the 200 ns multiplier value. The maximum variability over all operating conditions is ±20% (160 ns to 240 ns). Since normal Vsync and Hsync pulse widths differ by a factor of about 500 or more, the 20% variability is not an issue. counting Hsyncs per Vsync. The Hsync regenerator has a high degree of tolerance to extraneous and missing pulses on the Hsync input, but is not appropriate for use by the PLL in creating the pixel clock due to jitter. The Hsync regenerator runs automatically and requires no setup to operate. The Hsync filter requires the setting up of a filter window. The filter window sets a periodic window of time around the regenerated Hsync leading edge where valid Hsyncs are allowed to occur. The general idea is that extraneous pulses on the sync input occur outside of this filter window and thus are filtered out. In order to set the filter window timing, program a value (x) into Register 0x23. The resulting filter window time is ±x times 25 ns around the regenerated Hsync leading edge. Just as for the sync separator threshold multiplier, allow a ±20% variance in the 25 ns multiplier to account for all operating conditions (20 ns to 30 ns range). A second output from the Hsync filter is a status bit (0x25, Bit 1) that tells whether extraneous pulses were present on the incoming sync signal or not. Many times extraneous pulses are included for copy protection purposes, so this status bit can be used to detect that. The filtered Hsync (rather than the raw Hsync/SOGIN signal) for pixel clock generation by the PLL is controlled by Register 0x20, Bit 2. The regenerated Hsync (rather than the raw Hsync/ SOGIN signal) for the sync processing is controlled by Register 0x20, Bit 1. Use of the filtered Hsync and regenerated Hsync is recommended. See Figure 10 for an illustration of a filtered Hsync. Hsync Filter and Regenerator The Hsync filter is used to eliminate any extraneous pulses from the Hsync or SOGIN inputs, outputting a clean, low-jitter signal that is appropriate for mode detection and clock generation. The Hsync regenerator is used to recreate a clean, although not low jitter, Hsync signal that can be used for mode detection and Rev. 0 | Page 17 of 44 04739-015 COMPOSITE SYNC AT HSYNCIN AD9981 HSYNCIN Preliminary Technical Data FILTER WINDOW HSYNCOUT VSYNC EQUALIZATION PULSES EXPECTED EDGE FILTER WINDOW Figure 10. Sync Processing Filter Vsync Filter and Odd/Even Fields The Vsync filter is used to eliminate spurious Vsyncs, maintain a stable timing relationship between the Vsync and Hsync output signals, and generate the odd/even field output. The filter works by examining the placement of Vsync with respect to Hsync and if necessar y shifting it in time slightly. The goal is to keep the Vsync and Hsync leading edges from switching at the same time, thus eliminating confusion as to when the first line of a frame occurs. Register 0x14, Bit 2 enables the Vsync filter. Use of the Vsync filter is recommended for all cases, including interlaced video, and is required when using the Hsyncs per Vsync counter. Figure 12 illustrates even/odd field determination in two situations. SYNC SEPARATOR THRESHOLD FIELD 1 QUADRANT HSYNCIN VSYNCIN VSYNCOUT O/E FIELD 2 3 FIELD 0 4 1 FIELD 1 2 3 04739-016 FIELD 0 4 1 ODD FIELD Figure 11. Rev. 0 | Page 18 of 44 04739-017 AD9981 SYNC SEPARATOR THRESHOLD FIELD 1 QUADRANT HSYNCIN VSYNCIN VSYNCOUT O/E FIELD 2 3 FIELD 0 4 1 FIELD 1 2 3 FIELD 0 4 1 With manual power-down control, the polarity of the powerdown pin must be set (0x1E, Bit 2) regardless of whether the pin is used. If unused, it is recommended to set the polarity to active high and hardwire the pin to ground with a 10 kΩ resistor. In power-down mode, there are several circuits that continue to operate as normal. The serial register and sync detect circuits maintain power so that the AD9981 can be woken up from its power-down state. The bandgap circuit maintains power because it is needed for sync detection. The sync-on-green and SOGOUT functions continue to operate because the SOGOUT output is needed when sync detection is performed by a secondar y chip. All of these circuits require minimal power to operate. Typical standby power on the AD9981 is about 50 mW. There are two options that can be selected when in powerdown. These are controlled by Bits 0 and 1 in Register 0x1E. The first bit controls whether the SOGOUT pin is in high impedance or not. In most cases, the user will not place SOGOUT in high impedance during normal operation. The option to put SOGOUT in high impedance is included mainly to allow for factor y testing modes. The second option keeps the AD9981 powered up while placing only the outputs in high impedance. This option is useful when the data outputs from two chips are connected on a PCB and the user wants to switch instantaneously between the two. EVEN FIELD Figure 12. Vsync Filter—Odd/Even Power Management To meet display requirements for low standby power, the AD9981 includes a power-down mode. The power-down state can be controlled manually (via Pin 17 or Register 0x1E, Bit 3), or completely automatically by the chip. If automatic control is selected (0x1E, Bit 4), the AD9981’s decision is based on the status of the sync detect bits (Register 0x24, Bits 2, 3, 6, and 7). If either an Hsync or a sync-on-green input is detected on any input, the chip powers up, or else it powers down. For manual control, the AD9981 allows flexibility of control through both a dedicated pin and a register bit. The dedicated pin allows a hardware watchdog circuit to control power-down, while the register bit allows power-down to be controlled by software. Table 10. Power-Down Control and Mode Descriptions Inputs Mode Power-Up Power-Down Power-Up Power-Down Auto Power-Down Control1 1 1 0 0 Power-Down2 X X 0 1 04739-018 Sync Detect3 1 0 X X Powered-On or Comments Everything Only the serial bus, sync activity detect, SOG, bandgap reference Everything Only the serial bus, sync activity detect, SOG, bandgap reference 1 2 3 Auto power-down control is set by Register 0x1E, Bit 4. Power-down is controlled by OR’ing Pin 17 with Register 0x1E, Bit 3. The polarity of Pin 17 is set by Register 0x1E, Bit 2. Sync detect is determined by OR’ing Register 0x24, Bits 2, 3, 6, and 7. Rev. 0 | Page 19 of 44 AD9981 TIMING DIAGRAMS The following timing diagrams show the operation of the AD9981.The output data clock signal is created so that its rising edge always occurs between data transitions and can be used to tPER tDCYCLE DATACK Preliminary Technical Data latch the output data externally. There is a pipeline in the AD9981, which must be flushed before valid data becomes available. This means six data sets are presented before valid data is available. tSKEW 04739-007 DATA HSOUT Figure 13. Output Timing DATAIN P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 HSIN DATACLK 8 CLOCK CYCLE DELAY DATAOUT 2 CLOCK CYCLE DELAY HSOUT P0 P1 P2 P3 04739-008 Figure 14. 4:4:4 Timing Mode DATAIN P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 HSIN DATACLK 8 CLOCK CYCLE DELAY YOUT CB/CROUT 2 CLOCK CYCLE DELAY HSOUT 04739-009 Y0 B0 Y1 R0 Y2 B2 Y3 R2 1. PIXEL AFTER HSOUT CORRESONDS TO BLUE INPUT. 2. EVEN NUMBER OF PIXEL DELAY BETWEEN HSOUT AND DATAOUT (6 FOR THE AD9980). Figure 15. 4:2:2 Timing Mode Rev. 0 | Page 20 of 44 AD9981 DATAIN P0 P1 P2 P3 P4 P5 P6 P7 P8 P9 P10 P11 HSIN DATACLK 8 CLOCK CYCLE DELAY F0 R0 F1 R1 F2 R2 F3 R3 2 CLOCK CYCLE DELAY HSOUT DDR NOTES 1. OUTPUT DATACLK MAY BE DELAYED 1/4 CLOCK PERIOD IN THE REGISTERS. 2. SEE PROJECT DOCUMENT FOR VALUES OF F (FALLING EDGE) AND R (RISING EDGE). 3. FOR DDR 4:2:2 MODE: TIMING IS IDENTICAL, VALUES OF F AND R CHANGE. GENERAL NOTES 1. DATA DELAY MAY VARY ± ONE CLOCK CYCLE, DEPENDING ON PHASE SETTING. 2. ADCs SAMPLE INPUT ON FALLING EDGE OF DATACLK. 3. HSYNC SHOWN IS ACTIVE HIGH (EDGE SHOWN IS LEADING EDGE). 04739-010 Figure 16. DDR Timing Mode HSYNC TIMING The Hsync is processed in the AD9981 to eliminate ambiguity in the timing of the leading edge with respect to the phasedelayed pixel clock and data. The Hsync input is used as a reference to generate the pixel sampling clock. The sampling phase can be adjusted with respect to Hsync through a full 360° in 32 steps via the phase adjust register (to optimize the pixel sampling time). Display systems use Hsync to align memor y and display write cycles, so it is important to have a stable timing relationship between Hsync output (HSOUT) and the data clock (DATACK). Three things happen to Hsync in the AD9981. First, the polarity of Hsync input is determined and thus has a known output polarity. The known output polarity can be programmed either active high or active low (Register 0x12, Bit 3). Second, HSOUT is aligned with DATACK and data outputs. Third, the duration of HSOUT (in pixel clocks) is set via Register 0x13. HSOUT is the sync signal that should be used to drive the rest of the display system. The Coast input is provided to eliminate this problem. It is an asynchronous input that disables the PLL input and holds the clock at its current frequency. The PLL can free run for several lines without significant frequency drift. Coast can be generated internally by the AD9981 (see Register 0x18) or can be provided externally by the graphics controller. When internal Coast is selected (Register 0x18, Bit 7 = 0, and Register 0x14, Bits [7:6] to select source), Vsync is used as a basis for determining the position of Coast. The internal Coast signal is enabled a programmed number of Hsync periods before the periodic Vsync signal (Precoast Register 0x16) and dropped a programmed number of Hsync periods after Vsync (Postcoast Register 0x17). It is recommended that the Vsync filter be enabled when using the internal Coast function to allow the AD9981 to determine precisely the number of Hsyncs/Vsync and their location. In many applications where disruptions occur and Coast is used, values of 2 for Precoast and 10 DDR for Postcoast are sufficient to avoid most extraneous pulses. COAST TIMING In most computer systems, the Hsync signal is provided continuously on a dedicated wire. In these systems, the Coast input and function are unnecessar y and should not be used. In some systems, however, Hsync is disturbed during Vsync. In some cases, Hsync pulses disap-pear. In other systems, such as those that employ composite sync (Csync) signals or embedded sync-on-green, Hsync may include equalization pulses or other distortions during Vsync. To avoid upsetting the clock generator during Vsync, it is important to ignore these distortions. If the pixel clock PLL sees extraneous pulses, it attempts to lock to the new frequency and will have changed frequency by the end of the Vsync period. It then takes a few lines of correct Hsync timing to recover at the beginning of a new frame, resulting in a tearing of the image at the top of the display. OUTPUT FORMATTER The output formatter is capable of generating several output formats to be presented to the 30 data output pins. The output formats and the pin assignments for each format are listed in Table 11. Also, there are several clock options for the output clock. The user may select the pixel clock, a 90° phase-shifted pixel clock, a 2× pixel clock, or a fixed frequency 40 MHz clock for test purposes. The output clock may also be inverted. Data output is available as 30 pin RGB or YCbCr or if either 4:2:2 or 4:4:4 DDR is selected, a secondar y channel is available. This secondar y channel is always 4:2:2 DDR and allows the flexibility of having a second channel with the same video data that can be utilized by another display or a storage device. Depending on the choice of output modes, the primar y output can be 30 pins, 20 pins or as few as 15 pins. Rev. 0 | Page 21 of 44 AD9981 Mode Descriptions • 4:4:4—All channels come out with their 10 data bits at the same time. Data is aligned to the negative edge of the clock for easy capture. This is the normal 30-bit output mode for RGB or 4:4:4 YCbCr. 4:2:2—Red and green channels contain 4:2:2 formatted data (20 pins) with Y data on the green channel and Cb, Cr data on the red channel. Data is aligned to the negative edge of the clock. The blue channel contains the secondary channel with Cb, Y, Cr, Y formatted 4:2:2 DDR data. The data edges are aligned to both edges of the pixel clock, so use of the 90° clock may be necessary to capture the DDR data. • Preliminary Technical Data 4:4:4 DDR—This mode puts out full 4:4:4 data on 15 bits of the red and green channels, thus saving 15 pins. The first half (RGB [14:0]) of the 30-bit data is sent on the rising edge and the second half (RGB [29:15]) is sent on the falling edge. DDR 4:2:2 data is sent on the blue channel, as in 4:2:2 mode. RGB [29:0] = R [9:0] + G [9:0] + B [9:0], so RGB [29:15] = R [9:0] + G [9:5] and RGB [14:0] = G [4:0] + B [9:0] • Table 11. Output Formats Port Bit 4:4:4 4:2:21 4:4:4 DDR 9 8 7 6 Red 543 Red/Cr Cb, Cr DDR ↑2 G [4:0] DDR ↓ R [9:0] DDR ↑ B [9:0] DDR ↓ G [9:5] 2 1 0 9 8 7 6 Green 543 Green/Y Y N/A N/A 2 1 0 9 8 7 6 Blue 543 Blue/Cb 2 1 0 DDR 4:2:2 ↑ Cb, Cr ↓ Y,Y DDR 4:2:2 ↑ Cb,Cr DDR 4:2:2 ↓ Y,Y 1 2 For 4:2:2 modes, the first item in the list is the first pixel after Hsync. Arrows in the table indicate clock edge. Rising edge of clock = ↑, falling edge = ↓. Rev. 0 | Page 22 of 44 AD9981 TWO-WIRE SERIAL REGISTER MAP The AD9981 is initialized and controlled by a set of registers, which determine the operating modes. An external controller is employed to write and read the control registers through the two-wire serial interface port. Table 12. Control Register Map Hexadecimal Address 0x00 0x01 Read and Write or Read Only RO R/W Default Value 0110 1001 Bits 7:0 7:0 Register Name Chip Revision PLL Div MSB 0x02 0x03 R/W R/W 7:4 7:6 5:3 2 7:3 6:0 1101 **** 01** **** **00 1*** **** *0** 1000 0*** *100 0000 PLL Div LSB VCO/CPMP 0x04 0x05 R/W R/W Phase Adjust Red Gain MSBs 0x06 R/W 7:0 00** **** Red Gain LSBs 0x07 R/W 6:0 *100 0000 Green Gain MSBs Green Gain LSBs 0x08 R/W 7:0 00** **** 0x09 R/W 6:0 *100 0000 Blue Gain MSBs 0x0A R/W 7:0 00** **** Blue Gain LSBs 0x0B R/W 7:0 0100 0000 Red Offset MSBs 0x0C 0x0D R/W R/W 7 7:0 000* **** 0100 0000 Red Offset LSBs Green Offset MSBs Green Offset LSBs Blue Offset MSBs 0x0E R/W 7 000* **** 0x0F R/W 7:0 0100 0000 0x10 R/W 7 000* **** Blue Offset LSBs Description An 8-bit register that represents the silicon revision level. This register is for bits [11:4] of the PLL divider. Larger values mean the PLL operates at a faster rate. This register should be loaded first whenever a change is needed. (This will give the PLL more time to lock.)1 Bits [7:4] LSBs of the PLL Divider Word. Links to the PLL Div MSB to make a 12-bit register. Bits [7:6] VCO Range. Selects VCO frequency range. (See PLL description). Bits [5:3] Charge Pump Current. Varies the current that drives the low-pass filter. (See PLL description). Bit 2. External Clock Enable. ADC Clock Phase Adjustment. Larger values mean more delay. (1 LSB = T/32). 7-Bit Red Channel Gain Control. Controls ADC input range (contrast) of each respective channel. Bigger values give less contrast. Linked with Register 0x05 to form the 9-bit red gain that controls the ADC input range (contrast) of the red channel. A lower value corresponds to a higher gain. 7-Bit Green Channel Gain Control. Controls ADC input range (contrast) of each respective channel. Bigger values give less contrast. Linked to Register 0x07 to form the 9-bit green gain that controls the ADC input range (contrast) of the green channel. A lower value corresponds to a higher gain. 7-Bit Blue Channel Gain Control. Controls ADC input range (contrast) of each respective channel. Bigger values give less contrast. Linked to Register 0x09 to form the 9-bit blue gain that controls the ADC input range (contrast) of the blue channel. A lower value corresponds to a higher gain. 8-Bit MSBs of the Red Channel Offset Control. Controls dc offset (brightness) of each respective channel. Bigger values decrease brightness. Linked to Register 0x0B to form the 11-bit red offset that controls the dc offset (brightness) of the red channel in auto-offset mode. 8-Bit MSBs of the Green Channel Offset Control. Controls dc offset (brightness) of each respective channel. Bigger values decrease brightness. Linked to Register 0x0D to form the 11-bit green offset that controls the dc offset (brightness) of the green channel in autooffset mode. 8-Bit MSBs of the Red Channel Offset Control. Controls dc offset (brightness) of each respective channel. Bigger values decrease brightness. Linked to Register 0x0F to form the 11-bit blue offset which controls the dc offset (brightness) of the blue channel in autooffset mode. 1 1 1 1 1 1 1 Rev. 0 | Page 23 of 44 AD9981 Hexadecimal Address 0x11 0x12 Read and Write or Read Only R/W R/W Bits 7:0 7 Default Value 0010 0000 0*** **** Register Name Sync Separator Threshold Hsync Control Preliminary Technical Data Description This register sets the threshold of the sync separator’s digital comparator. Active Hsync Override. 0 = The chip determines the active Hsync source. 1 = The active Hsync Source is set by 0x12, Bit 6. Selects the source of the Hsync for PLL and sync processing. This bit is used only if 0x12, Bit 7 is set to 1 or if both syncs are active. 0 = Hsync is from Hsync input pin. 1 = Hsync is from SOG. Hsync Polarity Override. 0 = The chip selects the Hsync input polarity. 1 = The polarity of the input Hsync is controlled by 0x12, Bit 4. This applies to both Hsync0 and Hsync1. Hsync input polarity: this bit is used only if 0x12, Bit 5 is set to 1. 0 = Active low input Hsync. 1 = Active high input Hsync. Sets the polarity of the Hsync output signal. 0 = Active low Hsync output. 1 = Active high Hsync output. Sets the number of pixel clocks that Hsync out is active. Active Vsync Override. 0 = The chip determines the active Vsync source. 1 = The active Vsync source is set by 0x14, Bit 6. Selects the source of Vsync for the sync processing. This bit is used only if 0x14, Bit 7 is set to 1. 0 = Vsync is from the VSYNC input pin. 1 = Vsync is from the sync separator. Vsync Polarity Override. 0 = The chip selects the input Vsync polarity. 1 = The polarity of the input Vsync is set by 0x14, Bit 4. This applies to both Vsync0 and Vsync1. Vsync input polarity: this bit is used only if 0x14, Bit 5 is set to 1. 0 = Active low input Vsync. 1 = Active high input Vsync. Sets the polarity of the output Vsync signal. 0 = Active low output Vsync. 1 = Active high output Vsync. 0 = The Vsync filter is disabled. 1 = The Vsync filter is enabled. This needs to be enabled when using the Hsync to Vsync counter. Enables the Vsync duration block. This is designed to be used with the Vsync filter. 0 = Vsync output duration is unchanged. 1 = Vsync output duration is set by Register 0x15. Sets the number of Hsyncs that Vsync out is active. This is only used if 0x14, Bit 1 is set to 1. The number of Hsync periods to Coast prior to Vsync. The number of Hsync periods to Coast after Vsync. Coast Source. Selects the source of the Coast signal. 0 = Using internal Coast generated from Vsync. 1 = Using external Coast signal from external Coast pin. 6 *0** **** 5 **0* **** 4 ***1 **** 3 **** 1*** 0x13 0x14 R/W R/W 7:0 7 0010 0000 0*** **** Hsync Duration Vsync Control 6 *0** **** 5 **0* **** 4 ***1 **** 3 **** 1*** 2 **** *0** 1 **** **0* 0x15 0x16 0x17 0x18 R/W R/W R/W R/W 7:0 7:0 7:0 7 0000 1010 0000 0000 0000 0000 0*** **** Vsync Duration Precoast Postcoast Coast and Clamp Control Rev. 0 | Page 24 of 44 AD9981 Hexadecimal Address Read and Write or Read Only Bits 6 Default Value *0** **** Register Name Description Coast Polarity Override. 0 = The chip selects the external Coast polarity. 1 = The polarity of the external Coast signal is set by 0x18, Bit 5. Coast Input Polarity. This bit is used only if 0x18, Bit 6 is set to 1. 0 = Active low external Coast. 1 = Active high external Coast. Clamp Source Select. 0 = Use the internal clamp generated from Hsync. 1 = Use the external clamp signal. Red Clamp. 0 = Clamp the red channel to ground. 1 = Clamp the red channel to midscale. Green Clamp. 0 = Clamp the green channel to ground. 1 = Clamp the green channel to midscale. Blue Clamp. 0 = Clamp the blue channel to ground. 1 = Clamp the blue channel to midscale. Must be set to 0 for proper operation. Places the clamp signal an integer of clock periods after the trailing edge of the Hsync signal. Number of clock periods that the clamp signal is actively clamping. External clamp polarity override. 0 = The chip selects the clamp polarity. 1 = The polarity of the clamp signal is set by 0x1B, Bit 6. External Clamp Input Polarity. This bit is used only if 0x1B, Bit 7 is set to 1. 0 = Active low external clamp. 1 = Active high external clamp. 0 = Auto-offset is disabled. 1 = Auto-offset is enabled (offsets become the desired clamp code). This selects how often the auto-offset circuit operates. 00 = every clamp; 01 = 16 clamps; 10 = every 64 clamps; 11 = every Vsync. Must be written to default (011) for proper operation. Must be set to 0xFF for proper operation. SOG slicer threshold. Sets the voltage level of the SOG slicer’s comparator. SOGOUT Polarity. Sets the polarity of the signal on the SOGOUT pin. 0 = Active low SOGOUT. 1 = Active high SOGOUT. SOGOUT Select. 00 = Raw SOG from sync slicer (SOG0 or SOG1). 01 = Raw Hsync (Hsync0 or Hsync1). 10 = Regenerated sync from sync filter. 11 = Filtered sync from sync filter. Channel Select Override. 0 = The chip determines which input channels to use. 1 = The input channel selection is determined by 0x1E, Bit 6. Channel Select. Input channel select: this is used only if 0x1E, Bit 7 is set to 1, or if syncs are present on both channels. 0 = Channel 0 syncs and data are selected. 1 = Channel 1 syncs and data are selected. 5 **1* **** 4 ***0 **** 3 **** 0*** 2 **** *0** 1 **** **0* 0x19 0x1A 0x1B R/W R/W R/W 0 7:0 7:0 7 **** ***0 0000 1000 0010 0000 0*** **** Clamp Placement Clamp Duration Clamp and Offset 6 *1** **** 5 **0* **** 4:3 2:0 7:0 7:3 2 ***1 1*** **** *011 1111 1111 0111 1*** **** *0** 0x1C 0x1D R/W R/W TestReg0 SOG Control 1:0 **** **00 0x1E R/W 7 *** **** Power 6 *0** **** Rev. 0 | Page 25 of 44 AD9981 Hexadecimal Address Read and Write or Read Only Bits 5 Default Value **1* **** Register Name Preliminary Technical Data Description Programmable Bandwidth. 0 = Low analog input bandwidth. 1 = High analog input bandwidth. Power-Down Control Select. 0 = Manual power-down control. 1 = Auto power-down control. Power-Down. 0 = Normal operation. 1 = Power-down. Power-Down Pin Polarity. 0 = Active low. 1 = Active high. Power-Down Fast Switching Control. 0 = Normal power-down operation. 1 = The chip stays powered up and the outputs are put in high impedance mode. SOGOUT High Impedance Control. 0 = SOGOUT operates as normal during power-down. 1 = SOGOUT is in high impedance during power-down. Output Mode. 100 = 4:4:4 output mode. 101 = 4:2:2 output mode. 110 = 4:4:4—DDR output mode. Primary Output Enable. 0 = Primary output is in high impedance state. 1 = Primary output is enabled. Secondary Output Enable. 0 = Secondary output is in high impedance state. 1 = Secondary output is enabled. Output Drive Strength. 00 = Low output drive strength. 01 = Medium low output drive strength. 10 = Medium high output drive strength. 11 = High output drive strength. Applies to all outputs except VSOUT. Output Clock Invert. 0 = Noninverted pixel clock. 1 = Inverted pixel clock. Applies to all clocks output on DATACK. Output Clock Select. 00 = Pixel clock. 01 = 90° phase shifted pixel clock. 10 = 2× pixel clock. 11 = 40 MHz internal clock. Output High Impedance. 0 = Normal outputs. 1 = All outputs except SOGOUT in high impedance mode. SOG High Impedance. 0 = Normal SOG output. 1 = SOGOUT pin is in high impedance mode. Field Output Polarity. Sets the polarity of the field output signal. 0 = Active low => even field, active high => odd field. 1 = Active low => odd field, active high => even field. PLL Sync Filter Enable. 0 = PLL uses raw Hsync/SOG. 1 = PLL uses filtered Hsync/SOG. 4 ***1 **** 3 **** 0*** 2 **** *0** 1 **** **0* 0 **** ***0 0x1F R/W 7:5 100* **** Output Select 1 4 ***1 **** 3 **** 0*** 2:1 **** *10* 0 **** ***0 0x20 R/W 7:6 0*** **** Output Select 2 5 *0** **** 4 **0* **** 3 ***0 **** 2 **** 1*** Rev. 0 | Page 26 of 44 AD9981 Hexadecimal Address Read and Write or Read Only Bits 1 Default Value **** *0** Register Name Description Sync Processing Input Select. Selects the sync source for the sync processor. 0 = Sync processing uses raw Hsync/SOGIN. 1 = Sync processing uses regenerated Hsync from sync filter. Must be set to 1 for proper operation. Must be set to default for proper operation. Must be set to default for proper operation. Sets the window of time around the regenerated Hsync leading edge (in 25 ns steps) that sync pulses are allowed to pass through. Hsync0 Detection Bit. 0 = Hsync0 is not active. 1 = Hsync0 is active. Hsync1 Detection Bit. 0 = Hsync 1 is not active. 1 = Hsync 1 is active. Vsync 0 Detection Bit. 0 = Vsync0 is not active. 1 = Vsync0 is active. Vsync1 Detection Bit. 0 = Vsync1 is not active. 1 = Vsync1 is active. SOG0 Detection Bit 0 = SOG0 is not active. 1 = SOG0 is active. SOG1 Detection Bit 0 = SOG1 is not active. 1 = SOG1 is active. Coast Detection Bit. 0 = External Coast is not active. 1 = External Coast is active. Clamp Detection Bit. 0 = External clamp is not active. 1 = External clamp is active. Hsync 0 Polarity. 0 = Hsync0 polarity is active low. 1 = Hsync0 polarity is active high. Hsync1 Polarity. 0 = Hsync1 polarity is active low. 1 = Hsync1 polarity is active high. Vsync0 Polarity. 0 = Vsync0 polarity is active low. 1 = Vsync0 polarity is active high. Vsync1 Polarity. 0 = Vsync1 polarity is active low. 1 = Vsync1 polarity is active high. Coast Polarity. 0 = External Coast polarity is active low. 1 = External Coast polarity is active high. Clamp Polarity. 0 = External clamp polarity is active low. 1 = External clamp polarity is active high. Extraneous Pulses Detected. 0 = No equalization pulses detected on Hsync. 1 = Extraneous pulses detected on Hsync. 0x21 0x22 0x23 R/W R/W R/W 0 7:0 7:0 7:0 0010 0000 0011 0010 0000 1010 Sync Filter Window Width Sync Detect 0x24 RO 7 _*** **** 6 *_** **** 5 **_* **** 4 ***_ **** 3 **** _*** 2 **** *_** 1 **** **_* 0 **** ***_ 0x25 RO 7 _*** **** Sync Polarity Detect 6 *_** **** 5 **_* **** 4 ***_ **** 3 **** _*** 2 **** *_** 1 **** **_* Rev. 0 | Page 27 of 44 AD9981 Hexadecimal Address 0x26 0x27 0x28 0x29 0x2A 0x2B 0x2C Read and Write or Read Only RO RO R/W R/W RO RO R/W Bits 7:0 7:4 7:0 7:0 7:0 7:0 7:5 4 1011 1111 0000 0010 Default Value Register Name Hsyncs Per Vsync MSBs Hsyncs Per Vsync LSBs TestReg1 TestReg2 TestReg3 TestReg4 Offset Hold Preliminary Technical Data Description MSBs of Hsyncs per Vsync count. LSBs of Hsyncs per Vsync count. Must be written to 0xBF for proper operation. Must be written to 0x02 for proper operation. Read only bits for future use. Read only bits for future use. Must be written to default for proper operation. Auto-Offset Hold. Disables the auto-offset and holds the feedback result. 0 = One time update. 1 = Continuous update. Must be written to default for proper operation. Must be written to 0xE8 for proper operation. Must be written to 0xE0 for proper operation. 000* **** ***0 **** 0x2D 0x2E R/W R/W 3:0 7:0 7:0 **** 0000 1111 0000 1111 0000 TestReg5 TestReg6 1 Functions with more than eight control bits, such as PLL divide ratio, gain, and offset, are only updated when the LSBs are written to (for example, Register 0x02 for PLL divide ratio). Rev. 0 | Page 28 of 44 AD9981 DETAILED 2-WIRE SERIAL CONTROL REGISTER DESCRIPTIONS CHIP IDENTIFICATION 0x00 7:0 Chip Revision An 8-bit register that represents the silicon revision. CLOCK GENERATOR CONTROL 0x03 7:6 VCO Range Select Two bits that establish the operating range of the clock generator. VCORNGE must be set to correspond to the desired operating frequency (incoming pixel rate). The PLL gives the best jitter performance at high frequencies. For this reason, in order to output low pixel rates and still get good jitter performance, the PLL actually operates at a higher frequency but then divides down the clock rate afterwards. See Table 13 for the pixel rates for each VCO range setting. The PLL output divisor is automatically selected with the VCO range setting. The power-up default value is 01. Table 13. VCO Ranges VCO Range 00 01 10 11 Pixel Rates 10 to 21 21 to 42 42 to 84 84 to 95 PLL DIVIDER CONTROL 0x01 7:0 PLL Divide Ratio MSBs The eight MSBs of the 12-bit PLL divide ratio PLLDIV. The PLL derives a pixel clock from the incoming Hsync signal. The pixel clock frequency is then divided by an integer value, such that the output is phase-locked to Hsync. This PLLDIV value determines the number of pixel times (pixels plus horizontal blanking overhead) per line. This is typically 20% to 30% more than the number of active pixels in the display. The 12-bit value of the PLL divider supports divide ratios from 2 to 4095 as long as the output frequency is within range. The higher the value loaded in this register, the higher the resulting clock frequency with respect to a fixed Hsync frequency. VESA has established some standard timing specifications, which will assist in determining the value for PLLDIV as a function of horizontal and vertical display resolution and frame rate (see Table 9). However, many computer systems do not conform precisely to the recommendations and these numbers should be used only as a guide. The display system manufacturer should provide automatic or manual means for optimizing PLLDIV. An incorrectly set PLLDIV usually produces one or more vertical noise bars on the display. The greater the error, the greater the number of bars produced. The power-up default value of PLLDIV is 1693. PLLDIVM = 0x69, PLLDIVL = 0xDX. The AD9981 updates the full divide ratio only when the LSBs are written. Writing to this register by itself does not trigger an update. 0x02 7:4 PLL Divide Ratio LSBs 0x03 5:3 Charge Pump Current Three bits that establish the current driving the loop filter in the clock generator. The current must be set to correspond with the desired operating frequency. The power-up default value is current = 001. Table 14. Charge Pump Currents Ip2 0 0 0 0 1 1 1 1 Ip1 0 0 1 1 0 0 1 1 Ip0 0 1 0 1 0 1 0 1 Current 50 100 150 250 350 500 750 1500 0x03 2 External Clock Enable This bit determines the source of the pixel clock. Table 15. External Clock Select Settings EXTCLK 0 1 Function Internally generated clock Externally provided clock signal The four LSBs of the 12-bit PLL divide ratio PLLDIV. The power-up default value of PLLDIV is 1693. PLLDIVM = 0x69, PLLDIVL = 0xDX. A Logic 0 enables the internal PLL that generates the pixel clock from an externally provided Hsync. A Logic 1 enables the external EXTCLK input pin. In this mode, the PLL Divide Ratio (PLLDIV) is ignored. The clock phase adjust (PHASE) is still functional. The power-up default value is EXTCLK = 0. Rev. 0 | Page 29 of 44 AD9981 PHASE ADJUST 0x04 7:3 Phase adjustment for the DLL to generate the ADC clock. A 5-bit value that adjusts the sampling phase in 32 steps across one pixel time. Each step represents an 11.25° shift in sampling phase. The power up default is 16. Preliminary Technical Data INPUT OFFSET 0x0B 7:0 Red Channel Offset MSBs The 8-Bit MSB of the Red Channel Offset Control. Along with the 1 LSBs in the following register, there are 11 bits of dc offset control in the red channel. The offset control shifts the analog input, resulting in a change in brightness. Note that the function of the offset register depends on whether auto-offset is enabled (Register 0x1B, Bit 5). If auto-offset is disabled, the 9 bits of the offset registers (Bits [6:0] of the offset MSB register plus Bits [7:6] of the following register) control the absolute offset added to the channel (for the red channel, Register 0x0B, Bits[6:0] plus Register 0x0C, Bits [7:6]) control the absolute offset added to the channel. The offset control provides a ±255 LSBs of adjustment range, with 1 LSB of offset corresponding to 1 LSB of output code. If auto-offset is enabled, the 11-bit offset (comprised of the 8 bits of the MSB register and Bits [7:5] of the following register) determines the clamp target code. The 11-bit offset consists of 1 sign bit plus 10 bits. If the register is programmed to 530 DDR, then the output code is equal to 530 DDR at the end of the clamp period. Note that incrementing the offset register setting by 1 LSB adds 1 LSB of offset, regardless of the auto-offset setting. Values written to this register are not updated until the LSB register (Register 0x0C) has also been written. 0x0C 7:5 Red Channel Offset LSBs INPUT GAIN 0x05 6:0 Red Channel Gain Adjust MSBs The 7-Bit Red Channel Gain Control. The AD9981 can accommodate input signals with a full-scale range of between 0.5 V and 1.0 V p-p. Setting the red gain to 511 corresponds to an input range of 1.0 V. A red gain of 0 establishes an input range of 0.5 V. Note that increasing red gain results in the picture having less contrast (the input signal uses fewer of the available converter codes). Values written to this register will not be updated until the LSB register (R0x06) has also been written. The power-up default is 1000000. 0x06 7:6 Red Channel Gain Adjust LSBs The 2 Bit LSBs of the Red Channel Gain Control. Along with the 7 MSBs of gain control in the previous register, there are 9 bits of gain control. Default power up value is 00. 0x07 6:0 Green Channel Gain Adjust MSBs The 7-Bit Green Channel Gain Control. See red channel gain adjust above. Register update requires writing 0x00 to Register 0x08. 0x08 7:6 Green Channel Gain Adjust LSBs The 2-Bit LSBs of the Green Channel Gain Control. Along with the 7 MSBs of gain control in the previous register, there are 9 bits of gain control. Default powerup value is 00. 0x09 6:0 Blue Channel Gain Adjust MSBs The LSBs of the red channel offset control combine with the 8 bits of MSB in the previous register to make 11 bits of offset control. 0x0D 7:0 Green Channel Offset MSBs The 7-Bit Blue Channel Gain Control. See red channel gain adjust above. Register update requires writing 0x00 to Register 0x0A. 0x0A 7:6 Blue Channel Gain Adjust LSBs The 8-Bit Green Channel Offset Control. See red channel offset (0x0B). Update of this register occurs only when Register 0x0E is also written. 0x0E 7:5 Green Channel Offset LSBs The 2-Bit LSBs of the Blue Channel Gain Control. Along with the 7 MSBs of gain control in the previous register, there are 9 bits of gain control. Default powerup value is 00. The LSBs of the green channel offset control combine with the 8 bits of MSB in the previous register to make 11 bits of offset control. 0x0F 7:0 Blue Channel Offset MSBs The 8-Bit Blue Channel Offset Control. See red channel offset (0x0B). Update of this register occurs only when Register 0x10 is also written. Rev. 0 | Page 30 of 44 AD9981 0x10 7:5 Blue Channel Offset LSBs Table 18. Hsync Input Polarity Override Settings Override Bit 0 1 Result Hsync Polarity Determined by Chip Hsync Polarity Determined by User Register 0x12, Bit 4 The LSBs of the blue channel offset control combine with the 8 bits of MSB in the previous register to make 11 bits of offset control. HSYNC CONTROLS 0x11 7:0 Sync Separator Threshold This register sets the threshold of the sync separator’s digital comparator. The value written to this register is multiplied by 200 ns to get the threshold value. Therefore, if a value of 5 is written, the digital comparator threshold is 1 µs and any pulses less than 1 µS are rejected by the sync separator. There is some variability to the 200 ns multiplier value. The maximum variability over all operating conditions is ±20% (160 ns to 240 ns). Since normal Vsync and Hsync pulse widths differ by a factor of about 500 or more, the 20% variability is not an issue. The powerup default value is 32 DDR. 0x12 7 Hsync Source Override 0x12 4 Input Hsync Polarity If Bit 5 of Register 0x12 is 1, the value of this bit specifies the polarity of the input Hsync. Setting this bit to 0 indicates an active low Hsync; setting this bit to 1 indicates an active high Hsync. Power-up default is 1. Table 19. Hsync Input Polarity Settings Hsync Polarity Bit 0 1 Result Hsync Input Polarity is Negative Hsync Input Polarity is Positive 0x12 3 Hsync Output Polarity This bit sets the polarity of the Hsync output. Setting this bit to 0 sets the Hsync output to active low. Setting this bit to 1 sets the Hsync output to active high. Power-up default setting is 1. Table 20. Hsync Output Polarity Settings Hsync Output Polarity Bit 0 1 Result Hsync Output Polarity is Negative Hsync Output Polarity is Positive This is the active Hsync override. Setting this to 0 allows the chip to determine the active Hsync source. Setting it to 1 uses Bit 6 of Register 0x12 to determine the active Hsync source. Power-up default value is 0. Table 16.Active Hsync Source Override Override 0 1 Result Hsync Source determined by chip Hsync Source determined by user Register 0x12, Bit 6 0x13 7:0 Hsync Duration 0x12 6 Hsync Source This bit selects the source of the Hsync for PLL and sync processing—only if Bit 7 of Register 0x12 is set to 1 or if both syncs are active. Setting this bit to 0 specifies the Hsync from the input pin. Setting it to 1 selects Hsync from SOG. Power-up default is 0. Table 17. Active Hsync Select Settings Select 0 1 Result Hsync Input Hsync from SOG An 8-bit register that sets the duration of the Hsync output pulse. The leading edge of the Hsync output is triggered by the internally-generated, phase-adjusted PLL feedback clock. The AD9981 then counts a number of pixel clocks equal to the value in this register. This triggers the trailing edge of the Hsync output, which is also phase-adjusted. VSYNC CONTROLS 0x14 7 Vsync Source Override This is the active Vsync override. Setting this to 0 allows the chip to determine the active Vsync source, setting it to 1 uses Bit 6 of Register 0x14 to determine the active Vsync source. Power-up default value is 0. Table 21. Active Vsync Source Override Override 0 1 Result Vsync source determined by chip Vsync source determined by user Register 0x14, Bit 6 0x12 5 Hsync Input Polarity Override This bit determines whether the chip selects the Hsync input polarity or if it is specified. Setting this bit to 0 allows the chip to automatically select the polarity of the input Hsync; setting it to 1 indicates that Bit 4 of Register 0x12 specifies the polarity. Power-up default is 0. Rev. 0 | Page 31 of 44 AD9981 0x14 6 Vsync Source Vsync Filter Bit 0 1 Preliminary Technical Data Table 26. Vsync Filter Enable Result Vsync filter disabled Vsync filter enabled This bit selects the source of the Vsync for sync processing only if Bit 7 of Register 0x14 is set to 1. Setting Bit 6 to 0 specifies the Vsync from the input pin; setting it to 1 selects Vsync from the sync separator. Power-up default is 0. Table 22. Active Vsync Select Settings Select 0 1 Result Vsync input Vsync from sync separator 0x14 1 Vsync Duration Enable This enables the Vsync duration block, which is designed to be used with the Vsync filter. Setting the bit to 0 leaves the Vsync output duration unchanged. Setting the bit to 1 sets the Vsync output duration based on Register 0x15. Power-up duration is 0. Table 27. Vsync Duration Enable Vsync Duration Bit 0 1 Result Vsync output duration is unchanged Vsync output duration is set by Register 0x15 0x14 5 Vsync Input Polarity Override This bit sets whether the chip selects the Vsync input polarity or if it is specified. Setting this bit to 0 allows the chip to automatically select the polarity of the input Vsync. Setting this bit to 1 indicates that Bit 4 of Register 0x14 specifies the polarity. Power-up default is 0. Table 23. Vsync Input Polarity Override Settings Override Bit 0 1 Result Vsync polarity determined by chip Vsync polarity determined by user Register 0x14, Bit 4 0x15 7:0 Vsync Duration This is used to set the output duration of the Vsync, and is designed to be used with the Vsync filter. This is valid only if Register 0x14, Bit 1 is set to 1. Power-up default is 10 DDR. COAST AND CLAMP CONTROLS 0x16 7:0 Precoast This register allows the internally generated Coast signal to be applied prior to the Vsync signal. This is necessary in cases where pre-equalization pulses are present. The step size for this control is one Hsync period. For Precoast to work correctly, it is necessary for the Vsync filter (0x14, Bit 2) and sync processing filter (Register 0x20, Bit 1) both to be either enabled or disabled. The power-up default is 00. 0x17 7:0 Postcoast 0x14 4 Input Vsync Polarity If Bit 5 of Register 0x14 is 1, the value of this bit specifies the polarity of the input Vsync. Setting this bit to 0 indicates an active low Vsync; setting this bit to 1 indicates an active high Vsync. Power-up default is 1. Table 24. Vsync Input Polarity Settings Override Bit 0 1 Result Vsync input polarity is negative Vsync input polarity is positive 0x14 3 Vsync Output Polarity This register allows the internally generated Coast signal to be applied following the Vsync signal. This is necessary in cases where postequalization pulses are present. The step size for this control is one Hsync period. For Postcoast to work correctly, it is necessary for the Vsync filter (0x14, Bit 2) and sync processing filter (0x20, Bit 1) both to be either enabled or disabled. The power-up default is 00. 0x18 7 Coast Source This bit sets the polarity of the Hsync output. Setting this bit to 0 sets the Hsync output to active low. Setting this bit to 1 sets the Hsync output to active high. Power-up default is 1. Table 25. Vsync Output Polarity Settings Vsync Output Polarity Bit 0 1 Result Vsync output polarity is negative Vsync output polarity is positive 0x14 2 Vsync Filter Enable This bit enables the Vsync filter allowing precise placement of the Vsync with respect to the Hsync and facilitating the correct operation of the Hsyncs/ Vsync count. This bit is used to select the active Coast source. The choices are the COAST input pin or vsync. If Vsync is selected, the additional decision of using the VSYNC input pin or the output from the sync separator needs to be made (Register 0x14, Bits [7: 6]). Rev. 0 | Page 32 of 44 AD9981 Table 28. Coast Source Selection Settings Select 0 1 Result Vsync (internal Coast) COAST input pin Table 33. Green Clamp Select Settings Clamp 0 1 Result Clamp to ground Clamp to midscale 0x18 6 Coast Polarity Override 0x18 1 Blue Clamp Select This register is used to override the internal circuitry that determines the polarity of the Coast signal going into the PLL. The power-up default setting is 0. Table 29. Coast Polarity Override Settings Override Bit 0 1 Result Coast polarity determined by chip Coast polarity determined by user Clamp 0 1 This bit determines whether the blue channel is clamped to ground or to midscale. The power-up default setting is 0. Table 34. Blue Clamp Select Settings Result Clamp to ground Clamp to midscale 0x18 5 Input Coast Polarity 0x19 7:0 Clamp Placement This register sets the input Coast polarity when Bit 6 of Register 0x18 = 1. The power-up default setting is 1. Table 30. Coast Polarity Settings Coast Polarity Bit 0 1 Result Coast polarity is negative Coast polarity is positive 0x18 4 Clamp Source This bit determines the source of clamp timing. A 0 enables the clamp timing circuitry controlled by clamp placement and clamp duration. The clamp position and duration is counted from the leading edge of Hsync. A 1 enables the external clamp input pin. The three channels are clamped when the clamp signal is active. The polarity of clamp is determined by the clamp polarity bit. The power-up default setting is 0. Table 31. Clamp Source Selection Settings Clamp Source 0 1 Result Internally generated clamp Externally provided clamp signal An 8-bit register that sets the position of the internally generated clamp. When EXTCLMP = 0 (Register 0x18, Bit 4), a clamp signal is generated internally, at a position established by the clamp placement register (Register 0x19) and for a duration set by the clamp duration register (Register 0x1A). Clamping is started a clamp placement count(Register 0x19) of pixel periods after the trailing edge of Hsync. The clamp placement may be programmed to any value between 1 and 255. A value of 0 is not supported. The clamp should be placed during a time that the input signal presents a stable black-level reference, usually the back porch period between Hsync and the image. When EXTCLMP = 1, this register is ignored. Power-up default setting is 8. 0x1A 7:0 Clamp Duration 0x18 3 Red Clamp Select This bit determines whether the red channel is clamped to ground or to midscale. The power-up default setting is 0. Table 32. Red Clamp Select Settings Clamp 0 1 Result Clamp to ground Clamp to midscale An 8-bit register that sets the duration of the internally generated clamp. When EXTCLMP = 0 (Register 0x18, Bit 4), a clamp signal is generated internally at a position established by the clamp placement register (and for a duration set by the clamp duration register). Clamping begins a clamp placement count (Register 0x19) of pixel periods after the trailing edge of Hsync. The clamp duration may be programmed to any value between 1 and 255. A value of 0 is not supported. For the best results, the clamp duration should be set to include the majority of the black reference signal time that follows the Hsync signal trailing edge. Insufficient clamping time can produce brightness changes at the top of the screen, and a slow recovery from large changes in the average picture level (APL), or brightness. When EXTCLMP = 1, this register is ignored. Power-up default setting is 20 DDR. 0x18 2 Green Clamp Select This bit determines whether the green channel is clamped to ground or to midscale. The power-up default setting is 0. Rev. 0 | Page 33 of 44 AD9981 0x1B 7 Clamp Polarity Override 0x1D 2 This bit is used to override the internal circuitry that determines the polarity of the clamp signal. The power-up default setting is 0. Table 35. Clamp Polarity Override Settings Override Bit 0 1 Result Clamp Polarity Determined by Chip Clamp Polarity Determined by User Register 0x1B, Bit 6 Preliminary Technical Data SOG Output Polarity This bit sets the polarity of the SOGout signal. The power-up default setting is 0. Table 39. SOGOUT Polarity Settings SOGOUT 0 1 Result Active low Active high 0x1D 1:0 SOG Output Select 0x1B 6 Input Clamp Polarity This bit indicates the polarity of the clamp signal only if Bit 7 of Register 0x1B = 1. The power-up default setting is 1. Table 36. Clamp Polarity Override Settings CLMPOL 0 1 Result Active low Active high These register bits control what is output on the SOGOUT pin. Options are the raw SOG from the slicer (this is the unprocessed SOG signal produced from the sync slicer), the raw Hsync, the regenerated sync from the sync filter which can generate missing syncs either due to coasting or drop-out, or finally the filtered sync which excludes extraneous syncs not occurring within the sync filter window. The powerup default setting is 0. Table 40. SOGOUT Polarity Settings SOGOUT Select 00 01 10 11 Function Raw SOG from sync slicer (SOG0 or SOG1) Raw Hsync (HSYNC0 or HSYNC1) Regenerated Sync from sync filter Filtered sync from sync filter 0x1B 5 Auto-Offset Enable This bit selects between auto-offset mode and manual offset mode (auto-offset disabled). See the section on auto-offset operation. The power-up default setting is 0. Table 37. Auto-Offset Settings Auto-Offset 0 1 Result Auto-offset is disabled Auto-offset is enabled (manual offset mode) INPUT AND POWER CONTROL 0x1E 7 Channel Select Override This bit provides an override to the automatic input channel selection. Power-up default setting is 0. Table 41. Channel Source Override Override 0 1 Result Channel input source determined by chip Channel input source determined by user Register 0x1E, Bit 6 0x1B 4:3 Auto-Offset Update Frequency These bits control how often the auto-offset circuit is updated (if enabled). Updating every 64 Hsyncs is recommended. The power-up default setting is 11. Table 38. Auto-Offset Update Mode Clamp Update 00 01 10 11 Result Update offset every clamp period Update offset every 16 clamp periods Update offset every 64 clamp periods Update offset every Vsync periods 0x1E 6 Channel Select 0x1B 2-0 Must be written to 011 for proper operation. This bit selects the active input channel if Register 0x1E, bit 7 = 1. This selects between Channel 0 data and syncs or Channel 1 data and syncs. Power-up default setting is 0. Table 42. Channel Select Channel Select 0 1 Result Channel 0 data and syncs are selected Channel 1 data and syncs are selected SOG CONTROL 0x1D 7:3 SOG Comparator Threshold This register allows the comparator threshold of the SOG slicer to be adjusted. This register adjusts it in steps of 8 mV, with the minimum setting equaling 8 mV and the maximum setting equaling 256 mV. The power-up default setting is 15 DDR and corresponds to a threshold value of 128 mV. 0x1E 5 Programmable Bandwidth This bit selects between a low or high input bandwidth. It is useful in limiting noise for lower frequency inputs. The power-up default setting is 1. Low analog input bandwidth is ~100 MHz; high analog input bandwidth is ~200 MHz. Rev. 0 | Page 34 of 44 AD9981 Table 43. Input Bandwidth Select Input Bandwidth 0 1 Result Low analog input bandwidth High analog input bandwidth 0x1E 1 Power-Down Fast Switching Control 0x1E 4 Power-Down Control Select This bit determines whether power-down is controlled manually or automatically by the chip. If automatic control is selected (Register 0x1E, Bit 4), the AD9981’s decision is based on the status of the sync detect bits (Register 0x24, Bits 2, 3, 6, and 7). If either an Hsync or a sync-on-green input is detected on any input, the chip powers up or powers down. For manual control, the AD9981 allows the flexibility of control through both a dedicated pin and a register bit. The dedicated pin allows a hardware watchdog circuit to control power-down, while the register bit allows power-down to be controlled by software. With manual power-down control, the polarity of the powerdown pin must be set (0x1E, Bit 2) whether it is used or not. If unused, it is recommended to set the polarity to active high and hardwire the pin to ground with a 10 kΩ resistor. Table 44. Auto Power-Down Select Power-Down Select 0 1 Result Manual power-down control (User determines power-down) Auto power-down control (Chip determines power-down) This bit controls a special fast switching mode. With this bit the AD9981 can stay active during powerdown and only put the outputs in high impedance. This option is useful when the data outputs from two chips are connected on a PCB and the user wants to switch instantaneously between the two. Table 47. Power-Down Fast Switching Control Fast Switching Control 0 1 Result Normal power-down operation The chip stays powered up and the outputs are put in high impedance mode 0x1E 0 SOGOUT High Impedance Control This bit controls whether the SOGOUT output pin is in high impedance or not, when in power-down mode. In most cases, SOGOUT is not put in high impedance during normal operation. It is usually needed for sync detection by the graphics controller. The option to put SOGOUT in high impedance is included mainly to allow for factory testing modes. Table 42. SOGOUT High Impedance Control SOGOUT Control 0 1 Result The SOGOUT output operates as normal during power-down. The SOGOUT output is in high impedance during power-down. 0x1E 3 Power-Down OUTPUT CONTROL 0x1F 7:5 Output Mode These bits choose between three options for the output mode. In 4:4:4 mode, RGB is standard. In 4:2:2 mode, YCbCr is standard, which allows a reduction in the number of output pins from 30 to 20. In 4:4:4 DDR output mode, the data is in RGB mode, but changes on every clock edge. The power-up default setting is 100. Table 43. Output Mode Output Mode 100 101 110 Result 4:4:4 RGB mode 4:2:2 YCbCr mode 4:4:4 DDR mode This bit is used to manually place the chip in powerdown mode. It is only used if manual power-down control is selected (see Bit 4 above). Both the state of this register bit and the power-down pin (Pin 17) are used to control manual power-down. (See the Power Management section for more details on power-down.) Table 45. Power-Down Settings Power-Down Select 0 1 Pin 17 0 X Result Normal operation Power-down 0x1E 2 Power-Down Polarity This bit defines the polarity of the power-down pin (Pin 17). It is only used if manual power-down control is selected (see Bit 4 above). Table 46. Power-Down Pin Polarity Select 0 1 Result Power-down pin is active low Power-down pin is active high 0x1F 4 Primary Output Enable This bit places the primary output in active or high impedance mode. The power-up default setting is 1. Table 44. Primary Output Enable Select 0 1 Result Primary output is in high impedance mode Primary output is enabled Rev. 0 | Page 35 of 44 AD9981 0x1F 3 Secondary Output Enable 0x20 5 This bit places the secondary output in active or high impedance mode. The secondary output is designated when using either 4:2:2 or 4:4:4 (DDR). In these modes, the data on the blue output channel is the secondary output while the output data on the red and green channels are the primary output. Secondary output is always a DDR YCbCr data mode. See the Output Formatter section and Table 11. The power-up default setting is 0. Table 45. Secondary Output Enable Select 0 1 Result Secondary output is in high impedance mode Secondary output is enabled Preliminary Technical Data Output High Impedance This bit puts all outputs (except SOGOUT) in a high impedance state. The power-up default setting is 0. Table 49. Output High Impedance Select 0 1 Result Normal outputs All outputs (except SOGOUT) in high impedance mode 0x20 4 SOG High Impedance This bit allows the SOGOUT pin to be placed in high impedance mode. The power-up default setting is 0. Table 50. SOGOUT High Impedance Select 0 1 Result Normal SOG output SOGOUT pin is in high impedance mode 0x1F 2:1 Output Drive Strength These two bits select the drive strength for all the high-speed digital outputs (except VSOUT, A0, and the O/E field). Higher drive strength results in faster rise/fall times and in general makes it easier to capture data. Lower drive strength results in slower rise/fall times and helps to reduce EMI and digitally generated power supply noise. The power-up default setting is 10. Table 46. Output Drive Strength Output Drive 00 01 10 11 Result Low output drive strength Medium low output drive strength Medium high output drive strength High output drive strength 0x20 3 Field Output Polarity This bit sets the polarity of the field output bit. The power-up default setting is 1. Table 51. Field Output Polarity Select 0 1 Result Active low = even field; active high = odd field Active low = odd field; active high = even field SYNC PROCESSING 0x20 2 PLL Sync Filter 0x1F 0 Output Clock Invert This bit allows inversion of the output clock. The power-up default setting is 0. Table 47. Output Clock Invert Select 0 1 Result Noninverted pixel clock Inverted pixel clock This bit selects which signal the PLL uses. It can select between either raw Hsync or SOG or filtered versions. The filtering of the Hsync and SOG can eliminate nearly all extraneous transitions which have traditionally caused PLL disruption. The power-up default setting is 0. Table 52. PLL Sync Filter Enable Select 0 1 Result PLL uses raw Hsync or SOG inputs PLL uses filtered Hsync or SOG inputs 0x20 7:6 Output Clock Select 0x20 1 Sync Processing Input Source These bits allow selection of optional output clocks such as a fixed 40 MHz clock, a 2× clock, a 90° phaseshifted clock, or the normal pixel clock. The power-up default setting is 00. Table 48. Output Clock Select Select 00 01 10 11 Result Pixel clock 90° phase-shifted pixel clock 2× pixel clock 40 MHz internal clock This bit selects whether the sync processor uses a raw sync or a regenerated sync for the following functions: Coast, H/V count, field detection and Vsync duration counts. Using the regenerated sync is recommended. Table 53. SP Filter Enable Select 0 1 Result Sync processing uses raw Hsync or SOG Sync processing uses the internally regenerated Hsync Rev. 0 | Page 36 of 44 AD9981 0x21 0x22 0x23 7:0 7:0 7:0 Must be set to default Must be set to default Sync Filter Window Width activity is not detected. The sync processing block diagram shows where this function is implemented. 0 = Vsync1 not active. 1 = Vsync1 is active. Table 57. Vsync1 Detection Results Detect 0 1 Result No activity detected Activity detected This 8-bit register sets the window of time for the regenerated Hsync leading edge (in 25 ns steps) and that sync pulses are allowed to pass through. Therefore with the default value of 10, the window width is ±250 ns. The goal is to set the window width so that extraneous pulses are rejected. (see the Sync Processing section). As in the sync separator threshold, the 25 ns multiplier value is somewhat variable. The maximum variability over all operating conditions is ±20% (20 ns to 30 ns). 0x24 3 SOG0 Detection Bit This bit is used to indicate when activity is detected on the SOG0 input pin. If SOG is held high or low, activity is not detected. The sync processing block diagram shows where this function is implemented. 0 = SOG0 not active. 1 = SOG0 is active. Table 58. SOG0 Detection Results Detect 0 1 Result No activity detected Activity detected DETECTION STATUS 0x24 7 Hsync0 Detection Bit This bit is used to indicate when activity is detected on the HSYNC0 input pin. If Hsync is held high or low, activity is not detected. The sync processing block diagram shows where this function is implemented. 0 = Hsync0 not active. 1 = Hsync0 is active. Table 54. Hsync0 Detection Results Detect 0 1 Result No activity detected Activity detected 0x24 2 SOG1 Detection Bit This bit is used to indicate when activity is detected on the SOG1 input pin. If SOG is held high or low, activity is not detected. The sync processing block diagram shows where this function is implemented. 0 = SOG1 not active. 1 = SOG1 is active. Table 59. SOG1 Detection Results Detect 0 1 Result No activity detected Activity detected 0x24 6 Hsync1 Detection Bit This bit is used to indicate when activity is detected on the HSYNC1 input pin. If HSYNC is held high or low, activity is not detected. The sync processing block diagram shows where this function is implemented. 0 = HSYNC1 not active. 1 = HSYNC1 is active. Table 55. Hsync1 Detection Results Detect 0 1 Result No activity detected Activity detected 0x24 1 COAST Detection Bit This bit detects activity on the EXTCLK/EXTCOAST pin. It indicates that one of the two signals is active, but it doesn’t indicate which one. A dc signal is not detected. Table 60. Coast Detection Result Detect 0 1 Result No activity detected Activity detected 0x24 5 Vsync0 Detection Bit This bit is used to indicate when activity is detected on the VSYNC0 input pin. If Vsync is held high or low, activity is not detected. The sync processing block diagram shows where this function is implemented. 0 = Vsync0 not active. 1 = Vsync0 is active. Table 56. Vsync0 Detection Results Detect 0 1 Result No activity detected Activity detected 0x24 0 Clamp Detection Bit This bit is used to indicate when activity is detected on the external CLAMP pin. If external clamp is held high or low, activity is not detected. Table 61. Clamp Detection Results Detect 0 1 Result No activity detected Activity detected 0x24 4 VSYNC1 Detection Bit This bit is used to indicate when activity is detected on the VSYNC1 input pin. If Vsync is held high or low, Rev. 0 | Page 37 of 44 AD9981 POLARITY STATUS 0x25 7 Hsync0 Polarity Detect 0 1 Preliminary Technical Data Table 68. Equalization Pulse Detect Bit Result No equalization pulses detected during active Hsync Equalization pulses detected during active Hsync Indicates the polarity of the HSYNC0 input. Table 62. Detected Hsync0 Polarity Results Detect 0 1 Result Hsync polarity is negative Hsync polarity is positive HSYNC COUNT 0x26 7:0 Hsyncs/Vsync MSB 0x25 6 Hsync1 Polarity Indicates the polarity of HSYNC1 input. Table 63. Detected Hsync1 Polarity Results Detect 0 1 Result Hsync polarity is negative Hsync polarity is positive The eight MSBs of the 12-bit counter that reports the number of Hsyncs/Vsync on the active input. This is useful for determining the mode and is an aid in setting the PLL divide ratio. 0x27 7:4 Hsyncs/Vsync LSBs 0x25 5 Vsync0 Polarity The four LSBs of the 12-bit counter that reports the number of Hsyncs/Vsync on the active input. Indicates the polarity of Vsync0 input. Table 64. Detected Vsync0 Polarity Results Detect 0 1 Result Vsync polarity is negative Vsync polarity is positive Test Registers 0x28 7:0 Test Register 0 Must be written to 0xBF for proper operation. 0x29 7:0 Test Register 1 0x25 4 Vsync1 Polarity 0x2A Must be written to 0x00 for proper operation. 7:0 Test Register 2 Indicates the polarity of Vsync1 input. Table 65. Detected Vsync1 Polarity Results Detect 0 1 Result Vsync polarity is negative Vsync polarity is positive Read-only bits for future use. 0x2B 7:0 Test Register 3 0x25 3 Coast Polarity 0x2C Read-only bits for future use. 7:0 Test Register 4 Indicates the polarity of the external Coast signal. Table 66. Detected Coast Polarity Results Detect 0 1 Result Coast polarity is negative Coast polarity is positive Must be written to 0x00 for proper operation. 0x2C 4 Auto-Offset Hold 0x25 2 Clamp Polarity Indicates the polarity of the clamp signal. Table 67. Detected Clamp Polarity Results Detect 0 1 Result Clamp polarity is negative Clamp polarity is positive 0x25 1 Extraneous Pulses Detection A second output from the Hsync filter, this status bit tells whether extraneous pulses are present on the incoming sync signal. Often extraneous pulses are used for copy protection, so this status bit can be used for this purpose. A bit for controlling whether the auto-offset function runs continuously or runs once and holds the result. Continuous updates are recommended because it allows the AD9981 to compensate for drift-over time, temperature, and so on. If one-time updates are preferred, these should be performed every time the part is powered up and when there is a mode change. To do a one-time update, first auto-offset must be enabled (0x1B, Bit 5). Next, this bit (auto-offset hold) must be set to 1 to let the auto-offset function operate and settle to a final value. Auto-offset hold should then be set to 0 to hold the offset values that the auto circuitry calculates. The AD9981’s auto-offset circuit’s maxi-mum settle time is 10 updates. For example, if the update frequency is set to once every 64 Hsyncs, then the maximum settling time would be 640 Hsyncs (10 × 64 Hsyncs). Rev. 0 | Page 38 of 44 AD9981 Table 69. Auto-Offset Hold Select 0 1 Result Disables auto-offset updates and holds the current auto-offset values Allows auto-offset to update continuously 0x2C 0x2D 3:0 7:0 Must be written to 0x0 for proper operation. Test Register 5 Read/write bits for future use. Must be written to 0xE8 for proper operation. 0x2E 7:0 Test Register 6 Read/write bits for future use. Must be written to 0xE0 for proper operation. Rev. 0 | Page 39 of 44 AD9981 TWO-WIRE SERIAL CONTROL PORT A two-wire serial interface control interface is provided. Up to two AD9981 devices may be connected to the two-wire serial interface, with each device having a unique address. The two-wire serial interface comprises a clock (SCL) and a bidirectional data (SDA) pin. The analog flat panel interface acts as a slave for receiving and transmitting data over the serial interface. When the serial interface is not active, the logic levels on SCL and SDA are pulled high by external pull-up resistors. Data received or transmitted on the SDA line must be stable for the duration of the positive-going SCL pulse. Data on SDA must change only when SCL is low. If SDA changes state while SCL is high, the serial interface interprets that action as a start or stop sequence. The following are the five components to serial bus operation: • • • • • Start signal Slave address byte Base register address byte Data byte to read or write Stop signal Bit 7 A6 (MSB) 1 1 Bit 6 A5 0 0 Preliminary Technical Data Table 70. Serial Port Addresses Bit 5 A4 0 0 Bit 4 A3 1 1 Bit 3 A2 1 1 Bit 2 A1 0 0 Bit 1 A0 0 1 DATA TRANSFER VIA SERIAL INTERFACE For each byte of data read or written, the MSB is the first bit in the sequence. If the AD9981 does not acknowledge the master device during a write sequence, the SDA remains high so the master can generate a stop signal. If the master device does not acknowledge the AD9981 during a read sequence, the AD9981 interprets this as end-of-data. The SDA remains high so the master can generate a stop signal. Writing data to specific control registers of the AD9981 requires that the 8-bit address of the control register of interest be written after the slave address has been established. This control register address is the base address for subsequent write operations. The base address auto-increments by one for each byte of data written after the data byte intended for the base address. If more bytes are transferred than there are available addresses, the address will not increment and remain at its maximum value of 0x2E. Any base address higher than 0x2E will not produce an acknowledge signal. Data are read from the control registers of the AD9981 in a similar manner. Reading requires two data transfer operations: The base address must be written with the R/W bit of the slave address byte low to set up a sequential read operation. Reading (the R/W\ bit of the slave address byte high) begins at the previously established base address. The address of the read register auto-increments after each byte is transferred. To terminate a read/write sequence to the AD9981, a stop signal must be sent. A stop signal comprises a low-to-high transition of SDA while SCL is high. A repeated start signal occurs when the master device driving the serial interface generates a start signal without first generating a stop signal to terminate the current communication. This is used to change the mode of communication (read, write) between the slave and master without releasing the serial interface lines. When the serial interface is inactive (SCL and SDA are high), communications are initiated by sending a start signal. The start signal is a high-to-low transition on SDA while SCL is high. This signal alerts all slaved devices that a data transfer sequence is coming. The first eight bits of data transferred after a start signal comprise a 7-bit slave address (the first seven bits) and a single R/W\ bit (the eighth bit). The R/W\ bit indicates the direction of data transfer, read from 1 or write to 0 on the slave device. If the transmitted slave address matches the address of the device (set by the state of the Serial A0 address [SA0] input pin in Table 70), the AD9981 acknowledges the match by bringing SDA low on the 9th SCL pulse. If the addresses do not match, the AD9981 does not acknowledge it. SDA tBUFF tSTAH SCL tDHO tDAL tDSU tSTASU tSTOSU tDAH Figure 17. Serial Port Read/Write Timing Rev. 0 | Page 40 of 44 04739-011 AD9981 Serial Interface Read/Write Examples Write the following to one control register: • • • • • Start signal Slave address byte (R/W\bit = low) Base address byte Data byte to base address Stop signal Read from one control register: • • • • • • • Start signal Slave address byte (R/W\bit = low) Base address byte Start signal Slave address byte (R/W\ bit = high) Data byte from base address Stop signal Write to four consecutive control registers: • • • • • • • • Start signal Slave address byte (R/W\bit = low) Base address byte Data byte to base address Data byte to (base address + 1) Data byte to (base address + 2) Data byte to (base address + 3) Stop signal Read from four consecutive control registers: • • • • • • • • • • Start signal Slave address byte (R/W\bit = low) Base address byte Start signal Slave address byte (R/W\bit = high) Data byte from base address Data byte from (base address + 1) Data byte from (base address + 2) Data byte from (base address + 3) Stop signal SDA BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0 ACK 04739-012 SCL Figure 18. Serial Interface—Typical Byte Transfer Rev. 0 | Page 41 of 44 AD9981 PCB LAYOUT RECOMMENDATIONS The AD9981 is a high-precision, high-speed analog device. To achieve the maximum performance from the part, it is important to have a well laid-out board. The Analog Interface Inputs section provides a guide for designing a board using the AD9981. The bypass capacitors should be physically located between the power plane and the power pin. Current should flow from the power plane to the capacitor to the power pin. Do not make the power connection between the capacitor and the power pin. Placing a via underneath the capacitor pads, down to the power plane, is generally the best approach. It is particularly important to maintain low noise and good stability of the PVD (the clock generator supply). Abrupt changes in PVD can result in similarly abrupt changes in sampling clock phase and frequency. This can be avoided by careful attention to regulation, filtering, and bypassing. It is highly desirable to provide separate regulated supplies for each of the analog circuitry groups (VD and PVD). Some graphic controllers use substantially different levels of power when active (during active picture time) and when idle (during horizontal and vertical sync periods). This can result in a measurable change in the voltage supplied to the analog supply regulator, which can in turn produce changes in the regulated analog supply voltage. This can be mitigated by regulating the analog supply, or at least PVD, from a different, cleaner, power source (for example, from a 12 V supply). It is also recommended to use a single ground plane for the entire board. Experience has repeatedly shown that the noise performance is the same or better with a single ground plane. Using multiple ground planes can be detrimental because each separate ground plane is smaller and long ground loops can result. In some cases, using separate ground planes is unavoidable. For those cases, it is recommended to at least place a single ground plane under the AD9981. The location of the split should be at the receiver of the digital outputs. In this case it is even more important to place components wisely because the current loops will be much longer (current takes the path of least resistance). An example of a current loop is power plane to AD9981 to digital output trace to digital data receiver to digital ground plane to analog ground plane. Analog Interface Inputs Using the following layout techniques on the graphics inputs is extremely important: 1. Minimize the trace length running into the graphics inputs. This is accomplished by placing the AD9981 as close as possible to the graphics VGA connector. Long input trace lengths are undesirable because they pick up noise from the board and other external sources. Place the 75 Ω termination resistors (see Figure 3) as close as possible to the AD9981 chip. Any additional trace length between the termination resistors and the input of the AD9981 increases the magnitude of reflections, which corrupts the graphics signal. Use 75 Ω matched impedance traces. Trace impedances other than 75 Ω also increases the chance of reflections. The AD9981 has a very high input bandwidth, (200 MHz). While this is desirable for acquiring a high resolution PC graphics signal with fast edges, it also means that it captures any high frequency noise present. Therefore, it is important to reduce the amount of noise that gets coupled to the inputs. Avoid running any digital traces near the analog inputs. Due to the high bandwidth of the AD9981, sometimes low-pass filtering the analog inputs can help to reduce noise. (For many applications, filtering is unnecessary.) Experiments have shown that placing a ferrite bead in series prior to the 75 Ω termination resistor is helpful in filtering excess noise. Specifically, the Fair-Rite #2508051217Z0 was used, but an application could work best with a different bead value. Alternatively, placing a 100 Ω to 120 Ω resistor between the 75 Ω termination resistor and the input coupling capacitor is beneficial. 2. 3. 4. 5. PLL Place the PLL loop filter components as close to the FILT pin as possible. Do not place any digital or other high frequency traces near these components. Use the values suggested in the data sheet with 10% tolerances or less. Power Supply Bypassing It is recommended to bypass each power supply pin with a 0.1 µF capacitor. The exception is where two or more supply pins are adjacent to each other. For these groupings of powers/grounds, it is only necessary to have one bypass capacitor. The fundamental idea is to have a bypass capacitor within about 0.5 cm of each power pin. Also, avoid placing the capacitor on the opposite side of the PC board from the AD9981, since that interposes resistive vias in the path. Outputs (Both Data and Clocks) Try to minimize the trace length that the digital outputs have to drive. Longer traces have higher capacitance and require more instantaneous current to drive, which creates more internal digital noise. Shorter traces reduce the possibility of reflections. Rev. 0 | Page 42 of 44 AD9981 Adding a series resistor of value 50 Ω to 200 Ω can suppress reflections, reduce EMI, and reduce the current spikes inside of the AD9981. If series resistors are used, place them as close to the AD9981 pins as possible, (although try not to add vias or extra length to the output trace to get the resistors closer). If possible, limit the capacitance that each digital output drives to less than 10 pF. This is easily accomplished by keeping traces short and by connecting the outputs to only one device. Loading the outputs with excessive capacitance increases the current transients inside of the AD9981 and creates more digital noise on its power supplies. Digital Inputs Digital inputs on the AD9981 (HSYNC0, HSYNC1, VSYNC0, VSYNC1, SOGIN0, SOGIN1, SDA, SCL and CLAMP) were designed to work with 3.3 V signals, but are tolerant of 5.0 V signals. Therefore, no extra components need to be added if using 5.0 V logic. Any noise that gets onto the Hsync input trace adds jitter to the system. Therefore, minimize the trace length and do not run any digital or other high frequency traces near it. REFERENCE Bypass The AD9981 has three reference voltages that must be bypassed for proper operation of the input PGA. REFLO and REFHI are connected to each other through a 10 µF capacitor. REFCM is connected to ground through a 10 µF capacitor. These references are used by the input PGA circuitry to assure the greatest stability. Place them as close to the AD9981 pin as possible. Make the ground connection as short as possible. Rev. 0 | Page 43 of 44 AD9981 OUTLINE DIMENSIONS 0.75 0.60 0.45 SEATING PLANE 1.60 MAX 80 1 PIN 1 16.00 BSC SQ 61 60 TOP VIEW (PINS DOWN) 14.00 BSC SQ 1.45 1.40 1.35 10 ° 6° 2° 0.15 0.05 SEATING PLANE 0.20 0.09 7° 3. 5 ° 0° 0.10 MAX COPLANARITY VIEW A 20 21 40 41 0.65 BSC VIEW A ROTATED 90° CCW COMPLIANT TO JEDEC STANDARDS MS-026-BEC 0.38 0.32 0.22 Figure 19. 80-Lead Low Profile Quad Flat Pack [LQFP] (ST-80-2) Dimensions shown in millimeters ORDERING GUIDE Model AD9981KSTZ-801 AD9981KSTZ-951 AD9981/PCB Temperature Range 0°C to +70°C 0°C to +70°C Package Description 80-lead LQFP 80-lead LQFP Evaluation Kit Package Option ST-80-2 ST-80-2 1 Z = Pb-free part. Purchase of licensed I2C components of Analog Devices or one of its sublicensed Associated Companies conveys a license for the purchaser under the Philips I2C Patent Rights to use these components in an I2C system, provided that the system conforms to the I2C Standard Specification as defined by Philips. © 2005 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04739–0–1/05 0) Rev. 0 | Page 44 of 44