AD9575ARUZLVD

Network Clock Generator, Two Outputs AD9575 FEATURES GENERAL DESCRIPTION Fully integrated VCO/PLL core 0.39 ps rms jitter from 12 kHz to 20 MHz at 156.25 MHz 0.15 ps rms jitter from 1.875 MHz to 20 MHz at 156.25 MHz 0.40 ps rms jitter from 12 kHz to 20 MHz at 106.25 MHz 0.15 ps rms jitter from 637 kHz to 10 MHz at 106.25 MHz Input crystal frequency of 19.44 MHz, 25 MHz, or 25.78125 MHz Pin selectable divide ratios for 33.33 MHz, 62.5 MHz, 100 MHz, 106.25 MHz, 125 MHz, 155.52 MHz, 156.25 MHz, 159.375 MHz, 161.13 MHz, and 312.5 MHz outputs LVDS/LVPECL/LVCMOS output format Integrated loop filter Space saving 4.4 mm × 5.0 mm TSSOP 100 mA power supply current (LVDS output) 120 mA power supply current (LVPECL output) 3.3 V operation The AD9575 provides a highly integrated, dual output clock generator function including an on-chip PLL core that is optimized for network clocking. The integer-N PLL design is based on the Analog Devices, Inc., proven portfolio of high performance, low jitter frequency synthesizers to maximize line card performance. Other applications with demanding phase noise and jitter requirements also benefit from this part. The PLL section consists of a low noise phase frequency detector (PFD), a precision charge pump (CP), a low phase noise voltage controlled oscillator (VCO), and pin selectable feedback and output dividers. By connecting an external crystal, popular network output frequencies can be locked to the input reference. The output divider and feedback divider ratios are pin programmable for the required output rates. No external loop filter components are required, thus conserving valuable design time and board space. APPLICATIONS The AD9575 is available in a 16-lead, 4.4 mm × 5.0 mm TSSOP and can be operated from a single 3.3 V supply. The temperature range is −40°C to +85°C. GbE/FC/SONET line cards, switches, and routers CPU/PCI-E applications Low jitter, low phase noise clock generation FUNCTIONAL BLOCK DIAGRAM VDD × 5 LVDS OR LVPECL VCO DIVIDERS THIRD-ORDER LPF 100MHz TO 312.5MHz LVCMOS 33.33MHz/ 62.5MHz/SEL1 SEL AD9575 SEL0 GND × 5 08462-001 XTAL OSC PFD/CP LDO Figure 1. Rev. A 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: 781.461.3113 ©2010 Analog Devices, Inc. All rights reserved. AD9575 TABLE OF CONTENTS Features .............................................................................................. 1  Absolute Maximum Ratings ............................................................7  Applications ....................................................................................... 1  Thermal Resistance .......................................................................7  General Description ......................................................................... 1  ESD Caution...................................................................................7  Functional Block Diagram .............................................................. 1  Pin Configuration and Function Descriptions..............................8  Revision History ............................................................................... 2  Typical Performance Characteristics ..............................................9  Specifications..................................................................................... 3  Terminology .................................................................................... 11  PLL Characteristics ...................................................................... 3  Theory of Operation ...................................................................... 12  LVDS Clock Output Jitter (Typ/Max)........................................ 4  Phase Frequency Detector (PFD) and Charge Pump............ 12  LVPECL Clock Output Jitter (Typ/Max)................................... 4  Power Supply............................................................................... 12  Output Frequency Select ............................................................. 5  LVPECL Clock Distribution ..................................................... 12  Clock Outputs ............................................................................... 5  LVDS Clock Distribution .......................................................... 13  Timing Characteristics ................................................................ 5  LVCMOS Clock Distribution ................................................... 13  Power .............................................................................................. 6  Typical Application Circuit ....................................................... 13  Crystal Oscillator .......................................................................... 6  Outline Dimensions ....................................................................... 14  Timing Diagrams.......................................................................... 6  Ordering Guide .......................................................................... 14  REVISION HISTORY 3/10—Rev. 0 to Rev. A Changes to Features Section............................................................ 1 Changes to Table 1, Table 2, and Table 3 ....................................... 4 Changes to Table 4 and Table 6 ....................................................... 5 Changes to Table 7 and Table 8 ....................................................... 6 Changes to Table 12 .......................................................................... 8 Added Figure 11; Renumbered Figures Sequentially ................ 10 Changes to Figure 13 ...................................................................... 10 Changes to Theory of Operation Section and Figure 19........... 12 Changes to Figure 24 ...................................................................... 13 1/10—Revision 0: Initial Version Rev. A | Page 2 of 16 AD9575 SPECIFICATIONS Typical (typ) values are given for VS = 3.3 V ± 10%, TA = 25°C, unless otherwise noted. Minimum (min) and maximum (max) values are given over the full VS and TA (−40°C to +85°C) variation. PLL CHARACTERISTICS Table 1. Parameter PHASE NOISE CHARACTERISTICS PLL Noise (100 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (106.25 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (125 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (155.52 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (156.25 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (159.375 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz Min LVDS Typ LVPECL Typ Max Unit −123 −128 −131 −150 −156 −156 −122 −129 −131 −151 −158 −158 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −121 −127 −130 −149 −156 −156 −121 −128 −130 −150 −158 −159 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −120 −126 −128 −148 −155 −156 −120 −127 −129 −150 −157 −158 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −118 −123 −125 −147 −155 −156 −118 −123 −125 −149 −157 −157 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −118 −124 −126 −146 −155 −155 −118 −125 −127 −148 −157 −157 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −118 −124 −126 −146 −155 −155 −118 −125 −126 −147 −156 −157 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz Max Min Rev. A | Page 3 of 16 LVCMOS Typ Max Min AD9575 Parameter PLL Noise (161.132812 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (312.5 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 10 MHz At 30 MHz PLL Noise (33.33 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 5 MHz PLL Noise (62.5 MHz Output) At 1 kHz At 10 kHz At 100 kHz At 1 MHz At 5 MHz Spurious Content PLL Figure of Merit LVDS Typ Min LVPECL Typ Max Unit −118 −122 −126 −144 −154 −155 −119 −123 −126 −146 −156 −156 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −112 −119 −120 −140 −152 −153 −112 −119 −120 −142 −154 −155 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz Max Min LVCMOS Typ Max Min −131 −138 −140 −155 −155 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz −126 −133 −134 −150 −152 dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc/Hz dBc dBc/Hz −70 −217 −70 −217 LVDS CLOCK OUTPUT JITTER (TYP/MAX) Typical (typ) values are given for VS = 3.3 V ± 10%, TA = 25°C, unless otherwise noted. Maximum (max) values are given over the full VS and TA (−40°C to +85°C) variation. Table 2. Jitter Integration Bandwidth 12 kHz to 20 MHz 1.875 MHz to 20 MHz 637 kHz to 10 MHz 100 MHz 0.38/0.50 106.25 MHz 0.40/0.54 125 MHz 0.37/0.47 155.52 MHz 0.41/0.54 156.25 MHz 0.39/0.51 0.15/0.27 159.375 MHz 0.38/0.51 161.13 MHz 0.44/0.61 312.5 MHz 0.36/0.48 0.15/0.21 Unit ps rms ps rms ps rms LVPECL CLOCK OUTPUT JITTER (TYP/MAX) Typical (typ) values are given for VS = 3.3 V ± 10%, TA = 25°C, unless otherwise noted. Maximum (max) values are given over the full VS and TA (−40°C to +85°C) variation. Table 3. Jitter Integration Bandwidth 12 kHz to 20 MHz 1.875 MHz to 20 MHz 637 kHz to 10 MHz 100 MHz 0.36/0.46 106.25 MHz 0.44/0.68 125 MHz 0.36/0.45 155.52 MHz 0.40/0.52 0.22/0.35 Rev. A | Page 4 of 16 156.25 MHz 0.39/0.64 0.19/0.54 159.375 MHz 0.41/0.62 161.13 MHz 0.43/0.69 312.5 MHz 0.38/0.49 Unit ps rms ps rms ps rms AD9575 OUTPUT FREQUENCY SELECT Minimum (min) and maximum (max) values are given over the full VS and TA (−40°C to +85°C) variation. Table 4. Parameter Select Pins (SEL0/SEL1) Logic 1 Voltage Logic 0 Voltage Logic 1 Current Logic 0 Current Min Typ Max Unit Test Conditions/Comments 0.33 × VS − 0.2 190 150 V V μA μA Pull-up to VS Pull-down to GND 0.83 × VS + 0.2 CLOCK OUTPUTS Typical (typ) values are given for VS = 3.3 V ± 10%, TA = 25°C, unless otherwise noted. Minimum (min) and maximum (max) values are given over the full VS and TA (−40°C to +85°C) variation. Table 5. Parameter LVDS CLOCK OUTPUT Output Frequency Differential Output Voltage (VOD) Delta VOD Output Offset Voltage (VOS) Delta VOS Short-Circuit Current (ISA, ISB) Duty Cycle LVPECL CLOCK OUTPUT Output Frequency Output High Voltage (VOH) Output Low Voltage (VOL) Differential Output Voltage (VOD) Duty Cycle LVCMOS CLOCK OUTPUT Output Frequency Output High Voltage (VOH) Output Low Voltage (VOL) Duty Cycle Min Typ 250 340 1.125 1.25 45 VS − 1.5 VS − 2.5 430 45 Max Unit 14 50 312.5 450 25 1.375 25 24 55 MHz mV mV V mV mA % VS − 1.05 VS − 1.75 640 50 312.5 VS − 0.8 VS − 1.7 800 55 MHz V V mV % 62.5 45 50 0.1 55 MHz V V % Parameter LVDS Min Typ Max Unit Output Rise Time, tRL Output Fall Time, tFL LVPECL 150 150 200 200 300 300 ps ps Output Rise Time, tRL Output Fall Time, tFL LVCMOS 180 180 250 250 300 300 ps ps Output Rise Time, tRC Output Fall Time, tFC 0.50 0.50 0.70 0.70 1.10 1.10 ns ns VS − 0.1 Test Conditions/Comments Termination = 100 Ω differential; default See Figure 2 for definition Output shorted to GND See Figure 2 for definition TIMING CHARACTERISTICS Table 6. Rev. A | Page 5 of 16 Test Conditions/Comments Termination = 100 Ω differential; CLOAD = 0 pF; CAC = 0.1 μF 20% to 80%, measured differentially 80% to 20%, measured differentially Termination = 200 Ω to GND; CLOAD = 0 pF; CAC = 0.1 μF 20% to 80%, measured differentially 80% to 20%, measured differentially Termination = 50 Ω to 0 V; CLOAD = 5 pF; CAC = 0.1 μF 20% to 80% 80% to 20% AD9575 POWER Table 7. Parameter POWER SUPPLY POWER SUPPLY CURRENT LVDS LVPECL Min 3.0 Typ 3.3 Max 3.6 Unit V 100 120 130 160 mA mA CRYSTAL OSCILLATOR Table 8. Parameter CRYSTAL SPECIFICATION Frequency ESR Load Capacitance Phase Noise Stability Min Typ Max Unit 19.44 25 25.78125 40 MHz Ω pF dBc/Hz ppm 14 −138 −30 +30 Test Conditions/Comments Parallel resonant/fundamental mode Cx/2 (see Figure 24) + parasitic capacitance At 1 kHz offset TIMING DIAGRAMS DIFFERENTIAL SIGNAL SINGLE-ENDED 80% 80% 50% LVCMOS 5pF LOAD VOD 20% tFL tRC Figure 2. LVDS or LVPECL Timing and Differential Amplitude tFC Figure 3. LVCMOS Timing Rev. A | Page 6 of 16 08462-004 tRL 08462-003 20% AD9575 ABSOLUTE MAXIMUM RATINGS THERMAL RESISTANCE Table 9. Parameter VDD, VDDA, VDDX, VDD_CMOS to GND XO1, XO2 to GND LVDS/LVPECL OUT, LVDS/LVPECL OUT, CMOS OUT/SEL1, SEL0 to GND Junction Temperature1 Storage Temperature Range Lead Temperature (10 sec) 1 Rating −0.3 V to +3.6 V −0.3 V to VS + 0.3 V −0.3 V to VS + 0.3 V 150°C −65°C to +150°C 300°C θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 10. Thermal Resistance1 Package Type 16-Lead TSSOP (RU-16) 1 See Table 10 for θJA. θJA 90.3 Unit °C/W Thermal impedance measurements were taken on a 4-layer board in still air in accordance with EIA/JESD51-7. ESD CAUTION Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. Rev. A | Page 7 of 16 AD9575 PIN CONFIGURATION AND FUNCTION DESCRIPTIONS 16 SEL0 GNDA 1 VDDA 2 15 GND VDDX 3 14 LVDS/LVPECL OUT XO1 4 AD9575 XO2 5 TOP VIEW (Not to Scale) GNDX 6 11 VDD_CMOS GNDA 7 10 CMOS OUT/SEL1 VDDA 8 9 13 LVDS/LVPECL OUT GND_CMOS 08462-005 12 VDD Figure 4. Pin Configuration Table 11. Pin Function Descriptions Pin No. 1, 7 2, 8 3 4, 5 6 9 10 11 12 13 14 15 16 Mnemonic GNDA VDDA VDDX XO1, XO2 GNDX GND_CMOS CMOS OUT/SEL1 VDD_CMOS VDD LVDS/LVPECL OUT LVDS/LVPECL OUT GND SEL0 Description Analog Ground. Analog Power Supply (3.3 V). Crystal Oscillator Power Supply. External Crystal. Crystal Oscillator Ground. Ground for LVCMOS Output. LVCMOS Output/Output Frequency Select. Power Supply for LVCMOS Output. Power Supply for LVDS or LVPECL Output. Complementary LVDS or LVPECL Output. LVDS or LVPECL Output. Ground for LVDS or LVPECL Output. Output Frequency Select. Table 12. Output Frequency Selection 1 Mode 1 2 3 4 5 6 7 8 1 2 XTAL 25 MHz 25 MHz 25.78125 MHz 25 MHz 25 MHz 25 MHz 25 MHz 19.44 MHz SEL0 GND VS VS No connect 15 kΩ pull-up 15 kΩ pull-up VS VS SEL1 X2 GND GND X2 VS GND VS No connect X LVDS/LVPECL Output 100 MHz 156.25 MHz 161.13 MHz 125 MHz 159.375 MHz 312.5 MHz 106.25 MHz 155.52 MHz LVCMOS Output 33.33 MHz High-Z High-Z 62.5 MHz High-Z High-Z High-Z High-Z The AD9575 must be power-cycled if the select pin voltages are altered. X = in Mode 1, Pin 10 is configured as an LVCMOS output (33.33 MHz) by forcing Pin 16 to GND. In Mode 4, Pin 10 is configured as an LVCMOS output (62.5 MHz) by leaving Pin 16 unconnected. Rev. A | Page 8 of 16 AD9575 –110 –115 –115 –120 –120 –125 –130 –135 –140 –145 –135 –140 –145 –150 –155 –155 1M 10M 100M –160 1k –115 –115 –120 –120 PHASE NOISE (dBc/Hz) –110 –125 –130 –135 –140 –145 –135 –140 –145 –155 –155 100M FREQUENCY (Hz) –160 1k 08462-007 10M –110 –115 –120 –120 PHASE NOISE (dBc/Hz) –110 –125 –130 –135 –140 –145 –140 –145 FREQUENCY (Hz) 08462-008 –155 100M 100M –135 –155 10M 10M –130 –150 1M 1M –125 –150 100k 100k Figure 9. Phase Noise at LVPECL, 156.25 MHz Clock Output –115 10k 10k FREQUENCY (Hz) Figure 6. Phase Noise at LVPECL, 106.25 MHz Clock Output –160 1k 100M –130 –150 1M 10M –125 –150 100k 1M Figure 8. Phase Noise at LVPECL, 155.52 MHz Clock Output –110 10k 100k FREQUENCY (Hz) Figure 5. Phase Noise at LVPECL, 100 MHz Clock Output –160 1k 10k 08462-010 100k Figure 7. Phase Noise at LVPECL, 125 MHz Clock Output –160 1k 10k 100k 1M 10M 100M FREQUENCY (Hz) Figure 10. Phase Noise at LVPECL, 159.375 MHz Clock Output Rev. A | Page 9 of 16 08462-011 10k FREQUENCY (Hz) PHASE NOISE (dBc/Hz) –130 –150 –160 1k PHASE NOISE (dBc/Hz) –125 08462-009 PHASE NOISE (dBc/Hz) –110 08462-006 PHASE NOISE (dBc/Hz) TYPICAL PERFORMANCE CHARACTERISTICS AD9575 –110 –115 PHASE NOISE (dBc/Hz) –120 –125 –130 M2 –135 –140 –145 –150 10k 100k 1M 10M 100M FREQUENCY (Hz) M2 50mV 2ns M3 50mV 2ns 08462-022 –160 1k 08462-027 –155 Figure 14. 156.25 MHz LVDS Output Figure 11. Phase Noise at LVPECL, 161.13 MHz Clock Output –110 –115 PHASE NOISE (dBc/Hz) –120 –125 –130 M2 –135 –140 –145 –150 10k 100k 1M 10M 100M FREQUENCY (Hz) M2 100mV 1ns M3 100mV 1ns Figure 12. Phase Noise at LVPECL, 312.5 MHz Clock Output 08462-023 –160 1k 08462-012 –155 Figure 15. 312.5 MHz LVPECL Output 140 LVPECL 120 M2 110 LVDS 100 80 1 2 3 4 5 6 7 8 MODE Figure 13. Typical Supply Current vs. Mode (see Table 12) M2 100mV 10ns M3 100mV 10ns Figure 16. 62.5 MHz LVCMOS Output Rev. A | Page 10 of 16 08462-024 90 08462-021 SUPPLY CURRENT (mA) 130 AD9575 TERMINOLOGY Phase Jitter An ideal sine wave can be thought of as having a continuous and even progression of phase with time from 0° to 360° for each cycle. Actual signals, however, display a certain amount of variation from ideal phase progression over time. This phenomenon is called phase jitter. Although many causes can contribute to phase jitter, one major cause is random noise, which is characterized statistically as Gaussian (normal) in distribution. This phase jitter leads to a spreading out of the energy of the sine wave in the frequency domain, producing a continuous power spectrum. This power spectrum is usually reported as a series of values whose units are dBc/Hz at a given offset in frequency from the sine wave (carrier). The value is a ratio (expressed in decibels) of the power contained within a 1 Hz bandwidth with respect to the power at the carrier frequency. For each measurement, the offset from the carrier frequency is also given. Phase Noise It is meaningful to integrate the total power contained within some interval of offset frequencies (for example, 10 kHz to 10 MHz). This is called the integrated phase noise over that frequency offset interval and can be readily related to the time jitter due to the phase noise within that offset frequency interval. Phase noise has a detrimental effect on error rate performance by increasing eye closure at the transmitter output and reducing the jitter tolerance/sensitivity of the receiver. Time Jitter Phase noise is a frequency domain phenomenon. In the time domain, the same effect is exhibited as time jitter. When observing a sine wave, the time of successive zero crossings is seen to vary. In a square wave, the time jitter is seen as a displacement of the edges from their ideal (regular) times of occurrence. In both cases, the variations in timing from the ideal are the time jitter. Because these variations are random in nature, the time jitter is specified in units of seconds root mean square (rms) or 1 sigma of the Gaussian distribution. Additive Phase Noise Additive phase noise is the amount of phase noise that is attributable to the device or subsystem being measured. The phase noise of any external oscillators or clock sources is subtracted. This makes it possible to predict the degree to which the device affects the total system phase noise when used in conjunction with the various oscillators and clock sources, each of which contributes its own phase noise to the total. In many cases, the phase noise of one element dominates the system phase noise. Additive Time Jitter Additive time jitter is the amount of time jitter that is attributable to the device or subsystem being measured. The time jitter of any external oscillators or clock sources is subtracted. This makes it possible to predict the degree to which the device affects the total system time jitter when used in conjunction with the various oscillators and clock sources, each of which contributes its own time jitter to the total. In many cases, the time jitter of the external oscillators and clock sources dominates the system time jitter. Rev. A | Page 11 of 16 AD9575 THEORY OF OPERATION VDDX GNDX XTAL OSC VDDA GNDA VDD_CMOS GND_CMOS LVCMOS PHASE FREQUENCY DETECTOR 1/n CMOS OUT/SEL1 1/k LDO CHARGE PUMP LVDS/LVPECL OUT 1/m LVDS/LVPECL OUT 2.488GHz TO 2.55GHz VCO LVDS 100MHz 08462-015 AD9575 SEL0 SEL VLDO Figure 17. Detailed Block Diagram Figure 17 shows a block diagram of the AD9575. The chip features a PLL core, which is configured to generate the specific clock frequencies via pin programming. By appropriate connection of the select pins, SEL0 and SEL1, the divide ratios of the feedback divider (n), LVDS output divider (m), and LVCMOS output divider (k) can be programmed (see Table 12). In Mode 1 and Mode 4, Pin 10 is configured as an LVCMOS output by forcing Pin 16 to GND (33.33 MHz output) or by leaving Pin 16 unconnected (62.5 MHz output). In conjunction with a band-select VCO that operates over the range of 2.488 GHz to 2.55 GHz, a wide range of popular network reference frequencies can be generated. This PLL is based on proven Analog Devices synthesizer technology, noted for its exceptional phase noise performance. The AD9575 is highly integrated and includes the loop filter, a regulator for supply noise immunity, all the necessary dividers, output buffers, and a crystal oscillator. A user need only supply an external crystal to implement a clocking solution that requires no processor intervention. PHASE FREQUENCY DETECTOR (PFD) AND CHARGE PUMP POWER SUPPLY The AD9575 requires a 3.3 V ± 10% power supply for VS. The Specifications section gives the performance expected from the AD9575 with the power supply voltage within this range. The absolute maximum range of −0.3 V to +3.6 V, with respect to GND, must never be exceeded on the VDD, VDDA, VDDX, and VDD_CMOS pins. Good engineering practice should be followed in the layout of power supply traces and the ground plane of the PCB. The power supply should be bypassed on the PCB with adequate capacitance (>10 μF). The AD9575 should be bypassed with adequate capacitors (0.1 μF) at all power pins as close as possible to the part. The layout of the AD9575 evaluation board is a good example. LVPECL CLOCK DISTRIBUTION Because they are open emitter, the LVPECL outputs require a dc termination to bias the output transistors. The simplified equivalent circuit in Figure 19 shows the LVPECL output stage. VTERM The PFD takes inputs from the reference clock and feedback divider to produce an output proportional to the phase and frequency difference between them. Figure 18 shows a simplified schematic. 50Ω 50Ω LVPECL 50Ω CHARGE PUMP REFCLK 200Ω UP Figure 19. LVPECL AC-Coupled Termination CLR1 In most applications, a standard LVPECL far-end termination is recommended, as shown in Figure 20. The resistor network is designed to match the transmission line impedance (50 Ω) and the desired switching threshold (1.3 V). CP CLR2 DOWN D2 Q2 FEEDBACK DIVIDER GND 08462-016 HIGH 200Ω 08462-026 D1 Q1 LVPECL 0.1µF VP HIGH 50Ω 0.1µF Figure 18. PFD Simplified Schematic Rev. A | Page 12 of 16 AD9575 3.3V 127Ω 50Ω 127Ω SINGLE-ENDED (NOT COUPLED) LVPECL 3.3V LVPECL 50Ω 83Ω 83Ω 08462-025 VT = VDD – 1.3V Figure 20. LVPECL Far-End Termination LVDS CLOCK DISTRIBUTION CMOS MICROSTRIP 5pF GND Figure 22. Series Termination of LVCMOS Output Termination at the far end of the PCB trace is a second option. The LVCMOS output of the AD9575 does not supply enough current to provide a full voltage swing with a low impedance resistive, far-end termination, as shown in Figure 23. The far-end termination network should match the PCB trace impedance and provide the desired switching point. A recommended termination circuit for the LVDS outputs is shown in Figure 21. 50Ω 100Ω LVDS 08462-017 LVDS 50Ω 60.4Ω 1.0 INCH 10Ω The AD9575 is also available with low voltage differential signaling (LVDS) outputs. LVDS uses a current mode output stage with a factory programmed current level. The normal value (default) for this current is 3.5 mA, which yields a 350 mV output swing across a 100 Ω resistor. The LVDS outputs meet or exceed all ANSI/TIA/EIA-644 specifications. 08462-018 3.3V termination schemes and minimizes ringing due to possible mismatched impedances on the net. Series termination at the source is generally required to provide transmission line matching and/or to reduce current transients at the driver (see Figure 22). The value of the resistor is dependent on the board design and timing requirements (typically 10 Ω to 100 Ω is used). LVCMOS outputs are limited in terms of the capacitive load or trace length that they can drive. Typically, trace lengths less than 6 inches are recommended to preserve signal rise/fall times and preserve signal integrity. The reduced signal swing may still meet receiver input requirements in some applications. This can be useful when driving long trace lengths on less critical nets. Figure 21. LVDS Output Termination See the AN-586 Application Note on the Analog Devices website at www.analog.com for more information about LVDS. VPULLUP = 3.3V LVCMOS CLOCK DISTRIBUTION 10Ω The AD9575 provides a 33.33 MHz or 62.5 MHz clock output, which is a dedicated LVCMOS level. Whenever single-ended LVCMOS clocking is used, some of the following general guidelines should be followed. 100Ω 50Ω LVCMOS Figure 23. LVCMOS Output with Far-End Termination Point-to-point nets should be designed such that a driver has only one receiver on the net, if possible. This allows for simple TYPICAL APPLICATION CIRCUIT 0.1µF 1 GNDA 2 VDDA AD9575 SEL0 16 1nF VS VS Cx1 = 22pF GND 15 3 VDDX LVDS/LVPECL OUT 14 4 XO1 13 5 XO2 6 50Ω 0.1µF LVDS/LVPECL OUT 50Ω RT = 100Ω 0.1µF VDD 12 VS Cx2 = 22pF 11 GNDX VDD_CMOS 7 GNDA CMOS OUT/SEL1 10 8 VDDA GND_CMOS VS 0.1µF 9 Figure 24. Typical Application Circuit (in LVDS Configuration) Rev. A | Page 13 of 16 08462-028 0.1µF VS 3pF 08462-019 100Ω AD9575 OUTLINE DIMENSIONS 5.10 5.00 4.90 16 9 4.50 4.40 4.30 6.40 BSC 1 8 PIN 1 1.20 MAX 0.15 0.05 0.20 0.09 0.65 BSC 0.30 0.19 COPLANARITY 0.10 SEATING PLANE 8° 0° 0.75 0.60 0.45 COMPLIANT TO JEDEC STANDARDS MO-153-AB Figure 25. 16-Lead Thin Shrink Small Outline Package [TSSOP] (RU-16) Dimensions shown in millimeters ORDERING GUIDE Model 1 AD9575ARUZLVD Temperature Range −40°C to +85°C AD9575ARUZPEC −40°C to +85°C AD9575-EVALZ-LVD AD9575-EVALZ-PEC 1 Package Description 16-Lead Thin Shrink Small Outline Package (TSSOP), 96 pcs per Tube, LVDS Output Format 16-Lead Thin Shrink Small Outline Package (TSSOP), 96 pcs per Tube, LVPECL Output Format LVDS Outputs, Evaluation Board LVPECL Outputs, Evaluation Board Z = RoHS Compliant Part. Rev. A | Page 14 of 16 Package Option RU-16 RU-16 AD9575 NOTES Rev. A | Page 15 of 16 AD9575 NOTES ©2010 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D08462-0-3/10(A) Rev. A | Page 16 of 16