LTC2259IUJ-16

LTC2259-16 16-Bit, 80Msps Ultralow Power 1.8V ADC FEATURES n n n n n n n n n n n n DESCRIPTION The LTC®2259-16 is a sampling 16-bit A/D converter designed for digitizing high frequency, wide dynamic range signals. It is perfect for demanding communications applications with AC performance that includes 73.1dB SNR and 88dB spurious free dynamic range (SFDR). Ultralow jitter of 0.17psRMS allows undersampling of IF frequencies with excellent noise performance. DC specs include ±4LSB INL (typical) and ±0.5LSB DNL (typical). The digital outputs can be either full-rate CMOS, doubledata rate CMOS, or double-data rate LVDS. A separate output power supply allows the CMOS output swing to range from 1.2V to 1.8V. The ENC+ and ENC– inputs may be driven differentially or single ended with a sine wave, PECL, LVDS, TTL or CMOS inputs. An optional clock duty cycle stabilizer allows high performance at full speed for a wide range of clock duty cycles. L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. 73.1dB SNR 88dB SFDR Low Power: 89mW Single 1.8V Supply CMOS, DDR CMOS or DDR LVDS Outputs Selectable Input Ranges: 1VP-P to 2VP-P 800MHz Full-Power Bandwidth S/H Optional Data Output Randomizer Optional Clock Duty Cycle Stabilizer Shutdown and Nap Modes Serial SPI Port for Configuration 40-Pin (6mm × 6mm) QFN Package APPLICATIONS n n n n n n Communications Cellular Base Stations Software Defined Radios Portable Medical Imaging Multi-Channel Data Acquisition Nondestructive Testing TYPICAL APPLICATION 1.8V VDD 1.2V TO 1.8V OVDD 2-Tone FFT, fIN = 70MHz and 75MHz 0 –10 –20 AMPLITUDE (dBFS) –30 –40 –50 –60 –70 –80 + ANALOG INPUT INPUT S/H – 16-BIT PIPELINED ADC CORE CORRECTION LOGIC OUTPUT DRIVERS D15 CMOS • OR • LVDS • D0 OGND CLOCK/DUTY CYCLE CONTROL GND 225916 TA01a –90 –100 –110 –120 80MHz CLOCK 0 10 20 30 FREQUENCY (MHz) 40 225916 TA01b 225916f 1 LTC2259-16 ABSOLUTE MAXIMUM RATINGS (Notes 1, 2) Supply Voltages (VDD, OVDD) ....................... –0.3V to 2V Analog Input Voltage (AIN+, AIN –, PAR/SER, SENSE) (Note 3).......... –0.3V to (VDD + 0.2V) Digital Input Voltage (ENC+, ENC–, CS, SDI, SCK) (Note 4) .................................... –0.3V to 3.9V SDO (Note 4)............................................. –0.3V to 3.9V Digital Output Voltage ................ –0.3V to (OVDD + 0.3V) Operating Temperature Range: LTC2259C ................................................ 0°C to 70°C LTC2259I .............................................–40°C to 85°C Storage Temperature Range .................. –65°C to 150°C PIN CONFIGURATION D14_15 D12_13 SENSE FULL-RATE CMOS OUTPUT MODE TOP VIEW VREF VCM D15 D14 D13 D12 VDD D1 D0 DOUBLE DATA RATE CMOS OUTPUT MODE TOP VIEW SENSE D0_1 VREF DNC DNC DNC 30 D10_11 29 DNC 28 CLKOUT+ 27 CLKOUT– 41 GND 26 OVDD 25 OGND 24 D8_9 23 DNC 22 D6_7 21 DNC 11 12 13 14 15 16 17 18 19 20 CS SDO DNC D2_3 DNC SCK SDI D4_5 ENC+ ENC– VCM VDD 30 D11 29 D10 28 CLKOUT+ 27 CLKOUT– 41 GND 26 OVDD 25 OGND 24 D9 23 D8 22 D7 21 D6 11 12 13 14 15 16 17 18 19 20 CS SDO SCK SDI D2 D3 D4 ENC+ ENC– D5 AIN+ 1 AIN– 2 GND 3 REFH 4 REFH 5 REFL 6 REFL 7 PAR/SER 8 VDD 9 VDD 10 DOUBLE DATA RATE LVDS OUTPUT MODE TOP VIEW D14_15+ D14_15– D12_13+ D12_13– SENSE DO_1+ D0_1– VREF VCM VDD 40 39 38 37 36 35 34 33 32 31 AIN+ 1 AIN– 2 GND 3 REFH 4 REFH 5 REFL 6 REFL 7 PAR/SER 8 VDD 9 VDD 10 11 12 13 14 15 16 17 18 19 20 CS ENC+ ENC– SDO SCK SDI D2_3– D2_3+ D4_5– D4_5+ 41 GND 30 D10_11+ 29 D10_11– 28 CLKOUT+ 27 CLKOUT– 26 OVDD 25 OGND 24 D8_9+ 23 D8_9– 22 D6_7+ 21 D6_7– UJ PACKAGE 40-LEAD (6mm 6mm) PLASTIC QFN 40 39 38 37 36 35 34 33 32 31 AIN+ 1 AIN– 2 GND 3 REFH 4 REFH 5 REFL 6 REFL 7 PAR/SER 8 VDD 9 VDD 10 40 39 38 37 36 35 34 33 32 31 UJ PACKAGE 40-LEAD (6mm 6mm) PLASTIC QFN UJ PACKAGE 40-LEAD (6mm 6mm) PLASTIC QFN TJMAX = 150°C, θJA = 32°C/W EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB TJMAX = 150°C, θJA = 32°C/W EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB TJMAX = 150°C, θJA = 32°C/W EXPOSED PAD (PIN 41) IS GND, MUST BE SOLDERED TO PCB 225916f 2 LTC2259-16 ORDER INFORMATION LEAD FREE FINISH LTC2259CUJ-16#PBF LTC2259IUJ-16#PBF TAPE AND REEL LTC2259CUJ-16#TRPBF LTC2259IUJ-16#TRPBF PART MARKING* LTC2259UJ-16 LTC2259UJ-16 PACKAGE DESCRIPTION 40-Lead (6mm × 6mm) Plastic QFN 40-Lead (6mm × 6mm) Plastic QFN TEMPERATURE RANGE 0°C to 70°C –40°C to 85°C Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container. Consult LTC Marketing for information on non-standard lead based finish parts. For more information on lead free part marking, go to: http://www.linear.com/leadfree/ For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/ CONVERTER CHARACTERISTICS The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) CONDITIONS l PARAMETER Resolution (No Missing Codes) Integral Linearity Error Differential Linearity Error Offset Error Gain Error Offset Drift Full-Scale Drift Transition Noise MIN 16 –12 –1 –9 –1.5 l l l l TYP ±4 ±0.5 ±1.5 ±1.5 ±0.4 ±20 ±30 ±10 5 MAX 12 1.2 9 1.5 UNITS Bits LSB LSB mV %FS %FS μV/°C ppm/°C ppm/°C LSBRMS Differential Analog Input (Note 6) Differential Analog Input (Note 7) Internal Reference External Reference Internal Reference External Reference External Reference ANALOG INPUT SYMBOL PARAMETER VIN VINCM VSENSE IINCM IIN1 IIN2 IIN3 tAP tJITTER CMRR BW-3B The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) CONDITIONS 1.7V < VDD < 1.9V Differential Analog Input (Note 8) Per Pin, 80Msps 0 < AIN+, AIN– < VDD, No Encode 0 < PAR/SER < VDD 0.625 < SENSE < 1.3V l l l l l l MIN VCM – 100mV 0.625 –1 –3 –6 TYP 1 to 2 VCM 1.250 100 MAX VCM + 100mV 1.300 1 3 6 UNITS VP-P V V μA μA μA μA ns psRMS dB MHz Analog Input Range (AIN+ – AIN–) Analog Input Common Mode (AIN+ + AIN–)/2 Analog Input Common Mode Current Analog Input Leakage Current PAR/SER Input Leakage Current SENSE Input Leakage Current Sample-and-Hold Acquisition Delay Time Sample-and-Hold Acquisition Delay Jitter Analog Input Common Mode Rejection Ratio Full-Power Bandwidth External Voltage Reference Applied to SENSE External Reference Mode 0 0.17 80 Figure 6 Test Circuit 800 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 5) SYMBOL SNR PARAMETER Signal-to-Noise Ratio CONDITIONS 5MHz Input 70MHz Input 140MHz Input l DYNAMIC ACCURACY MIN 70.9 TYP 73.1 72.9 72.4 MAX UNITS dBFS dBFS dBFS 225916f 3 LTC2259-16 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. AIN = –1dBFS. (Note 5) SYMBOL SFDR PARAMETER Spurious Free Dynamic Range 2nd or 3rd Harmonic Spurious Free Dynamic Range 4th Harmonic or Higher S/(N+D) Signal-to-Noise Plus Distortion Ratio CONDITIONS 5MHz Input 70MHz Input 140MHz Input 5MHz Input 70MHz Input 140MHz Input 5MHz Input 70MHz Input 140MHz Input l DYNAMIC ACCURACY MIN 79 TYP 88 85 82 90 90 90 72.9 72.6 72 MAX UNITS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS dBFS l 85 l 70.4 INTERNAL REFERENCE CHARACTERISTICS PARAMETER VCM Output Voltage VCM Output Temperature Drift VCM Output Resistance VREF Output Voltage VREF Output Temperature Drift VREF Output Resistance VREF Line Regulation –400μA < IOUT < 1mA 1.7V < VDD < 1.9V –600μA < IOUT < 1mA IOUT = 0 CONDITIONS IOUT = 0 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) MIN 0.5 • VDD – 25mV TYP 0.5 • VDD ±25 4 1.225 1.250 ±25 7 0.6 1.275 MAX 0.5 • VDD + 25mV UNITS V ppm/°C Ω V ppm/°C Ω mV/V DIGITAL INPUTS AND OUTPUTS SYMBOL PARAMETER ENCODE INPUTS (ENC+, ENC– ) Differential Encode Mode (ENC– Not Tied to GND) VID VICM VIN RIN CIN VIH VIL VIN RIN CIN VIH VIL IIN CIN Differential Input Voltage Common Mode Input Voltage Input Voltage Range Input Resistance Input Capacitance High Level Input Voltage Low Level Input Voltage Input Voltage Range Input Resistance Input Capacitance High Level Input Voltage Low Level Input Voltage Input Current Input Capacitance (Note 8) The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) CONDITIONS MIN TYP MAX UNITS l l l 0.2 1.2 1.1 0.2 10 3.5 1.6 3.6 V V V V kΩ pF V 0.6 V V kΩ pF V 0.6 V μA pF 225916f Internally Set Externally Set (Note 8) ENC+, ENC– to GND (See Figure 10) (Note 8) VDD = 1.8V VDD = 1.8V ENC+ to GND (See Figure 11) (Note 8) VDD = 1.8V VDD = 1.8V VIN = 0V to 3.6V (Note 8) Single-Ended Encode Mode (ENC– Tied to GND) l l l 1.2 0 30 3.5 3.6 DIGITAL INPUTS (CS, SDI, SCK) l l l 1.3 –10 3 10 4 LTC2259-16 DIGITAL INPUTS AND OUTPUTS SYMBOL PARAMETER ROL IOH COUT Logic Low Output Resistance to GND Logic High Output Leakage Current Output Capacitance The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) CONDITIONS VDD = 1.8V, SDO = 0V SDO = 0V to 3.6V (Note 8) l MIN TYP 200 MAX UNITS Ω SDO OUTPUT (Open-Drain Output. Requires 2k Pull-Up Resistor if SDO is Used) –10 4 10 μA pF DIGITAL DATA OUTPUTS (CMOS MODES: FULL DATA RATE AND DOUBLE-DATA RATE) OVDD = 1.8V VOH VOL VOH VOL VOH VOL VOD VOS RTERM High Level Output Voltage Low Level Output Voltage High Level Output Voltage Low Level Output Voltage High Level Output Voltage Low Level Output Voltage Differential Output Voltage Common Mode Output Voltage On-Chip Termination Resistance IO = –500μA IO = 500μA IO = –500μA IO = 500μA IO = –500μA IO = 500μA 100Ω Differential Load, 3.5mA Mode 100Ω Differential Load, 1.75mA Mode 100Ω Differential Load, 3.5mA Mode 100Ω Differential Load, 1.75mA Mode Termination Enabled, OVDD = 1.8V l l l l 1.750 1.790 0.010 1.488 0.010 1.185 0.010 0.050 V V V V V V 454 1.375 mV mV V V Ω OVDD = 1.5V OVDD = 1.2V DIGITAL DATA OUTPUTS (LVDS MODE) 247 1.125 350 175 1.250 1.250 100 The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 9) SYMBOL VDD OVDD IVDD IOVDD PDISS PARAMETER Analog Supply Voltage Output Supply Voltage Analog Supply Current Digital Supply Current Power Dissipation CONDITIONS (Note 10) (Note 10) DC Input Sine Wave Input Sine Wave Input, OVDD=1.2V DC Input Sine Wave Input, OVDD=1.2V (Note 10) (Note 10) Sine Wave Input Sine Input, 1.75mA Mode Sine Input, 3.5mA Mode Sine Input, 1.75mA Mode Sine Input, 3.5mA Mode l l l l POWER REQUIREMENTS MIN 1.7 1.1 TYP 1.8 49.2 50.2 2.5 89 93 MAX 1.9 1.9 58.1 UNITS V V mA mA mA mW mW V V mA mA mA mW mW mW mW mW 225916f CMOS Output Modes: Full Data Rate and Double-Data Rate 105 LVDS Output Mode VDD OVDD IVDD IOVDD PDISS Analog Supply Voltage Output Supply Voltage Analog Supply Current Digital Supply Current (0VDD = 1.8V) Power Dissipation l l l l l l l 1.7 1.7 1.8 53.8 20.7 40.5 134 170 0.5 9 10 1.9 1.9 63.5 26 47.8 161 201 All Output Modes PSLEEP PNAP PDIFFCLK Sleep Mode Power Nap Mode Power Power Increase with Differential Encode Mode Enabled (No increase for Nap or Sleep Modes) 5 LTC2259-16 TIMING CHARACTERISTICS SYMBOL fS tL tH tAP PARAMETER Sampling Frequency ENC Low Time (Note 8) ENC High Time (Note 8) Sample-and-Hold Acquisition Delay Time ENC to Data Delay ENC to CLKOUT Delay DATA to CLKOUT Skew Pipeline Latency Digital Data Outputs (LVDS Mode) tD tC tSKEW ENC to Data Delay ENC to CLKOUT Delay DATA to CLKOUT Skew Pipeline Latency SPI Port Timing (Note 8) tSCK tS tH tDS tDH tDO SCK Period CS to SCK Setup Time SCK to CS Setup Time SDI Setup Time SDI Hold Time SCK Falling to SDO Valid Readback Mode, CSDO = 20pF RPULLUP = 2k , Write Mode Readback Mode, CSDO = 20pF RPULLUP = 2k , l l l l l l l The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. (Note 5) CONDITIONS (Note 10) Duty Cycle Stabilizer Off Duty Cycle Stabilizer On Duty Cycle Stabilizer Off Duty Cycle Stabilizer On l l l l l MIN 1 5.93 2.00 5.93 2.00 TYP 6.25 6.25 6.25 6.25 0 MAX 80 500 500 500 500 UNITS MHz ns ns ns ns ns Digital Data Outputs (CMOS Modes: Full Data Rate and Double-Data Rate) tD tC tSKEW CL = 5pF (Note 8) CL = 5pF (Note 8) tD – tC (Note 8) Full Data Rate Mode Double-Data Rate Mode CL = 5pF (Note 8) CL = 5pF (Note 8) tD – tC (Note 8) l l l l l l 1.1 1 0 1.7 1.4 0.3 5.0 5.5 3.1 2.6 0.6 ns ns ns Cycles Cycles 1.1 1 0 1.8 1.5 0.3 5.5 3.2 2.7 0.6 ns ns ns Cycles ns ns ns ns ns ns 40 250 5 5 5 5 125 ns Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. Exposure to any Absolute Maximum Rating condition for extended periods may affect device reliability and lifetime. Note 2: All voltage values are with respect to GND with GND and OGND shorted (unless otherwise noted). Note 3: When these pin voltages are taken below GND or above VDD, they will be clamped by internal diodes. This product can handle input currents of greater than 100mA below GND or above VDD without latchup. Note 4: When these pin voltages are taken below GND they will be clamped by internal diodes. When these pin voltages are taken above VDD they will not be clamped by internal diodes. This product can handle input currents of greater than 100mA below GND without latchup. Note 5: VDD = OVDD = 1.8V, fSAMPLE = 80MHz, LVDS outputs with internal termination disabled, differential ENC+/ENC– = 2VP-P sine wave, input range = 2VP-P with differential drive, unless otherwise noted. Note 6: Integral nonlinearity is defined as the deviation of a code from a best fit straight line to the transfer curve. The deviation is measured from the center of the quantization band. Note 7: Offset error is the offset voltage measured from –0.5 LSB when the output code flickers between 0000 0000 0000 0000 and 1111 1111 1111 1111 in 2’s complement output mode. Note 8: Guaranteed by design, not subject to test. Note 9: VDD = 1.8V, fSAMPLE = 80MHz, ENC+ = single-ended 1.8V square wave, ENC– = 0V, input range = 2VP-P with differential drive, 5pF load on each digital output unless otherwise noted. Note 10: Recommended operating conditions. 225916f 6 LTC2259-16 TIMING DIAGRAMS Full-Rate CMOS Output Mode Timing All Outputs Are Single-Ended and Have CMOS Levels tAP ANALOG INPUT N tH tL ENC– ENC+ tD D0-D15 tC N–5 N–4 N–3 N–2 N–1 N+1 N+2 N+3 N+4 CLKOUT + CLKOUT – 225916 TD01 Double-Data Rate CMOS Output Mode Timing All Outputs Are Single-Ended and Have CMOS Levels tAP ANALOG INPUT N tH tL ENC– ENC+ tD D0_1 D0N-5 D1N-5 D0N-4 tD D1N-4 D0N-3 D1N-3 D0N-2 D1N-2 N+1 N+2 N+3 N+4 • • • D14_15 D14N-5 D15N-5 D14N-4 D15N-4 D14N-3 D15N-3 D14N-2 D15N-2 CLKOUT+ CLKOUT – tC tC 225916 TD02 225916f 7 LTC2259-16 TIMING DIAGRAMS Double-Data Rate LVDS Output Mode Timing All Outputs Are Differential and Have LVDS Levels tAP ANALOG INPUT N tH tL ENC– ENC+ D0_1+ D0_1– D14_15+ D14_15– CLKOUT+ CLKOUT – D14N-5 tC D15N-5 D14N-4 D15N-4 tC D14N-3 D15N-3 D14N-2 D15N-2 tD D0N-5 D1N-5 D0N-4 tD D1N-4 D0N-3 D1N-3 D0N-2 D1N-2 N+1 N+2 N+3 N+4 • • • 225916 TD03 SPI Port Timing (Readback Mode) tS CS SCK tDO SDI SDO HIGH IMPEDANCE R/W A6 A5 A4 A3 A2 A1 A0 XX D7 XX D6 XX D5 XX D4 XX D3 XX D2 XX D1 XX D0 tDS tDH tSCK tH SPI Port Timing (Write Mode) CS SCK SDI SDO R/W A6 A5 A4 A3 A2 A1 A0 D7 D6 D5 D4 D3 D2 D1 D0 HIGH IMPEDANCE 226114 TD04 225916f 8 LTC2259-16 TYPICAL PERFORMANCE CHARACTERISTICS LTC2259-16: Integral Non-Linearity (INL) 4 3 2 DNL ERROR (LSB) INL ERROR (LSB) 1 0 –1 –2 –3 –4 0 16384 32768 49152 OUTPUT CODE 65536 225916 G01 LTC2259-16: Differential Non-Linearity (DNL) 1.0 0.8 0.6 AMPLITUDE (dBFS) 0.4 0.2 0 –0.2 –0.4 –0.6 –0.8 –1.0 0 16384 32768 49152 OUTPUT CODE 65536 225916 G02 LTC2259-16: 8k Point FFT, fIN = 5MHz –1dBFS, 80Msps 0 –10 –20 –30 –40 –50 –60 –70 –80 –90 –100 –110 –120 0 10 20 30 FREQUENCY (MHz) 40 225916 G03 LTC2259-16: 8k Point FFT, fIN = 30MHz –1dBFS, 80Msps 0 –10 –20 –30 AMPLITUDE (dBFS) AMPLITUDE (dBFS) –40 –50 –60 –70 –80 0 –10 –20 –30 –40 –50 –60 –70 –80 LTC2259-16: 8k Point FFT, fIN = 70MHz –1dBFS, 80Msps –90 –100 –110 –120 0 10 20 30 FREQUENCY (MHz) 40 225916 G04 –90 –100 –110 –120 0 10 20 30 FREQUENCY (MHz) 40 225916 G05 LTC2259-16: 8k Point FFT, fIN = 140MHz –1dBFS, 80Msps 0 –10 –20 AMPLITUDE (dBFS) AMPLITUDE (dBFS) –30 –40 –50 –60 –70 –80 0 –10 –20 –30 –40 –50 –60 –70 –80 LTC2259-16: 8k Point 2-Tone FFT, fIN = 70MHz, 75MHz, –1dBFS, 80Msps –90 –100 –110 –120 0 10 20 30 FREQUENCY (MHz) 40 225916 G06 –90 –100 –110 –120 0 10 20 30 FREQUENCY (MHz) 40 225916 G07 225916f 9 LTC2259-16 TYPICAL PERFORMANCE CHARACTERISTICS LTC2259-16: SNR vs Input Frequency, –1dBFS, 2V Range, 80Msps 74 73 72 SFDR (dBFS) SNR (dBFS) 71 70 69 68 67 66 0 50 100 150 200 250 300 INPUT FREQUENCY (MHz) 350 70 65 85 80 75 95 90 SFDR (dBc AND dBFS) LTC2259-16: SFDR vs Input Frequency, –1dBFS, 2V Range, 80Msps 110 100 90 80 70 60 50 40 30 20 10 0 50 100 150 200 250 300 INPUT FREQUENCY (MHz) 350 LTC2259-16: SFDR vs Input Level, fIN = 70MHz, 2V Range, 80Msps dBFS dBc 0 –80 –70 –60 –50 –40 –30 –20 –10 INPUT LEVEL (dBFS) 0 225916 G08 225916 G09 225916 G10 LTC2259-16: IVDD vs Sample Rate, 5MHz Sine Wave Input, –1dBFS 55 45 40 50 IVDD (mA) LVDS OUTPUTS IOVDD (mA) 35 30 25 20 15 10 5 35 0 20 40 60 SAMPLE RATE (Msps) 80 225916 G11 LTC2259-16: IOVDD vs Sample Rate, 5MHz Sine Wave Input, –1dBFS, 5pF on Each Data Output 74 3.5mA LVDS 73 72 SNR (dBFS) 80 225916 G12 LTC2259-16: SNR vs SENSE, fIN = 5MHz, –1dBFS 71 70 69 68 45 CMOS OUTPUTS 40 1.75mA LVDS 1.2V CMOS 1.8V CMOS 0 20 40 60 SAMPLE RATE (Msps) 67 66 0.6 0.7 0.8 0.9 1 1.1 SENSE PIN (V) 1.2 1.3 0 225916 G13 225916f 10 LTC2259-16 PIN FUNCTIONS PINS THAT ARE THE SAME FOR ALL DIGITAL OUTPUT MODES AIN+ (Pin 1): Positive Differential Analog Input. AIN– (Pin 2): Negative Differential Analog Input. GND (Pin 3, Exposed Pad Pin 41): ADC Power Ground. REFH (Pins 4, 5): ADC High Reference. Bypass to Pins 6, 7 with a 2.2μF ceramic capacitor and to ground with a 0.1μF ceramic capacitor. REFL (Pins 6, 7): ADC Low Reference. Bypass to Pins 4, 5 with a 2.2μF ceramic capacitor and to ground with a 0.1μF ceramic capacitor. PAR/SER (Pin 8): Programming Mode Selection Pin. Connect to ground to enable the serial programming mode. CS, SCK, SDI, SDO become a serial interface that control the A/D operating modes. Connect to VDD to enable the parallel programming mode where CS, SCK, SDI become parallel logic inputs that control a reduced set of the A/D operating modes. PAR/SER should be connected directly to ground or the VDD of the part and not be driven by a logic signal. VDD (Pins 9, 10, 40): 1.8V Analog Power Supply. Bypass to ground with 0.1μF ceramic capacitors. Pins 9 and 10 can share a bypass capacitor. ENC+ (Pin 11): Encode Input. Conversion starts on the rising edge. ENC– (Pin 12): Encode Complement Input. Conversion starts on the falling edge. CS (Pin 13): In serial programming mode, (PAR/SER = 0V), CS is the serial interface chip select input. When CS is low, SCK is enabled for shifting data on SDI into the mode control registers. In the parallel programming mode (PAR/SER = VDD), CS controls the clock duty cycle stabilizer. When CS is low, the clock duty cycle stabilizer is turned off. When CS is high, the clock duty cycle stabilizer is turned on. CS can be driven with 1.8V to 3.3V logic. SCK (Pin 14): In serial programming mode, (PAR/SER = 0V), SCK is the serial interface clock input. In the parallel programming mode (PAR/SER = VDD), SCK controls the digital output mode. When SCK is low, the full-rate CMOS output mode is enabled. When SCK is high, the doubledata rate LVDS output mode (with 3.5mA output current) is enabled. SCK can be driven with 1.8V to 3.3V logic. SDI (Pin 15): In serial programming mode, (PAR/SER = 0V), SDI is the serial interface data input. Data on SDI is clocked into the mode control registers on the rising edge of SCK. In the parallel programming mode (PAR/SER = VDD), SDI can be used to power down the part. When SDI is low, the part operates normally. When SDI is high, the part enters sleep mode. SDI can be driven with 1.8V to 3.3V logic. SDO (Pin 16): In serial programming mode, (PAR/SER = 0V), SDO is the optional serial interface data output. Data on SDO is read back from the mode control registers and can be latched on the falling edge of SCK. SDO is an open-drain NMOS output that requires an external 2k pull-up resistor to 1.8V-3.3V. If read back from the mode control registers is not needed, the pull-up resistor is not necessary and SDO can be left unconnected. In the parallel programming mode (PAR/SER = VDD), SDO is not used and should not be connected. OGND (Pin 25): Output Driver Ground. OVDD (Pin 26): Output Driver Supply. Bypass to ground with a 0.1μF ceramic capacitor. VCM (Pin 37): Common Mode Bias Output, Nominally Equal to VDD/2. VCM should be used to bias the common mode of the analog inputs. Bypass to ground with a 0.1μF ceramic capacitor. VREF (Pin 38): Reference Voltage Output. Bypass to ground with a 1μF ceramic capacitor, nominally 1.25V. SENSE (Pin 39): Reference Programming Pin. Connecting SENSE to VDD selects the internal reference and a ±1V input range. Connecting SENSE to ground selects the internal reference and a ±0.5V input range. An external reference between 0.625V and 1.3V applied to SENSE selects an input range of ±0.8 • VSENSE. 225916f 11 LTC2259-16 PIN FUNCTIONS FULL-RATE CMOS OUTPUT MODE All Pins Below Have CMOS Output Levels (OGND to OVDD) D0 to D15 (Pins 35, 36, 17-24, 29-34): Digital Outputs. D15 is the MSB. D0 is the LSB. CLKOUT– (Pin 27): Inverted Version of CLKOUT+. CLKOUT+ (Pin 28): Data Output Clock. The digital outputs normally transition at the same time as the falling edge of CLKOUT+. The phase of CLKOUT+ can also be delayed relative to the digital outputs by programming the mode control registers. DOUBLE-DATA RATE CMOS OUTPUT MODE All Pins Below Have CMOS Output Levels (OGND to OVDD) D0_1 to D14_15 (Pins 36,18, 20, 22, 24, 30, 32, 34): Double-Data Rate Digital Outputs. Two data bits are multiplexed onto each output pin. The even data bits (D0, D2, D4, D6, D8, D10, D12, D14) appear when CLKOUT+ is low. The odd data bits (D1, D3, D5, D7, D9, D11, D13, D15) appear when CLKOUT+ is high. CLKOUT– (Pin 27): Inverted Version of CLKOUT+. CLKOUT+ (Pin 28): Data Output Clock. The digital outputs normally transition at the same time as the falling and rising edges of CLKOUT+. The phase of CLKOUT+ can also be delayed relative to the digital outputs by programming the mode control registers. DNC (Pins 17, 19, 21, 23, 29, 31, 33, 35): Do not connect these pins. DOUBLE-DATA RATE LVDS OUTPUT MODE All Pins Below Have LVDS Output Levels. The Output Current Level is Programmable. There is an Optional Internal 100Ω Termination Resistor Between the Pins of Each LVDS Output Pair. D0_1–/D0_1+ to D14_15–/D14_15+ (Pins 35/36, 17/18, 19/20, 21/22, 23/24, 29/30, 31/32, 33/34): Double-Data Rate Digital Outputs. Two data bits are multiplexed onto each differential output pair. The even data bits (D0, D2, D4, D6, D8, D10, D12, D14) appear when CLKOUT+ is low. The odd data bits (D1, D3, D5, D7, D9, D11, D13, D15) appear when CLKOUT+ is high. CLKOUT–/CLKOUT+ (Pins 27/28): Data Output Clock. The digital outputs normally transition at the same time as the falling and rising edges of CLKOUT+. The phase of CLKOUT+ can also be delayed relative to the digital outputs by programming the mode control registers. 225916f 12 LTC2259-16 FUNCTIONAL BLOCK DIAGRAM AIN+ INPUT S/H FIRST PIPELINED ADC STAGE SECOND PIPELINED ADC STAGE THIRD PIPELINED ADC STAGE FOURTH PIPELINED ADC STAGE FIFTH PIPELINED ADC STAGE VDD GND AIN– VCM 0.1μF VREF 1μF RANGE SELECT 1.25V REFERENCE VDD/2 SHIFT REGISTER AND CORRECTION SENSE REF BUF REFH REFL INTERNAL CLOCK SIGNALS OVDD D15 DIFF REF AMP CLOCK/DUTY CYCLE CONTROL MODE CONTROL REGISTERS OUTPUT DRIVERS • • • D0 CLKOUT + CLKOUT – REFH 0.1μF REFL ENC+ ENC– PAR/SER CS SCK SDI SDO OGND 225916 F01 2.2μF 0.1μF 0.1μF Figure 1. Functional Block Diagram APPLICATIONS INFORMATION CONVERTER OPERATION The LTC2259-16 is a low power 16-bit 80Msps A/D converter that is powered by a single 1.8V supply. The analog inputs should be driven differentially. The encode input can be driven differentially, or single ended for lower power consumption. The digital outputs can be CMOS, double-data rate CMOS (to halve the number of output lines), or double-data rate LVDS (to reduce digital noise in the system.) Many additional features can be chosen by programming the mode control registers through a serial SPI port. See the Serial Programming Mode section. ANALOG INPUT The analog input is a differential CMOS sample-and-hold circuit (Figure 2). The inputs should be driven differentially around a common mode voltage set by the VCM output pin, which is nominally VDD/2. For the 2V input range, the inputs should swing from VCM – 0.5V to VCM + 0.5V. There should be 180° phase difference between the inputs. AIN+ LTC2259-16 VDD 10Ω CPARASITIC 1.8pF RON 25Ω CPARASITIC 1.8pF VDD CSAMPLE 3.5pF RON 25Ω CSAMPLE 3.5pF VDD 10Ω AIN– 1.2V 10k ENC+ ENC– 10k 1.2V 225916 F02 Figure 2. Equivalent Input Circuit 225916f 13 LTC2259-16 APPLICATIONS INFORMATION INPUT DRIVE CIRCUITS Input Filtering If possible, there should be an RC lowpass filter right at the analog inputs. This lowpass filter isolates the drive circuitry from the A/D sample-and-hold switching, and also limits wideband noise from the drive circuitry. Figure 3 shows an example of an input RC filter. The RC component values should be chosen based on the application’s input frequency. Transformer-Coupled Circuits Figure 3 shows the analog input being driven by an RF transformer with a center-tapped secondary. The center tap is biased with VCM, setting the A/D input at its optimal DC level. At higher input frequencies a transmission line balun transformer (Figures 4 to 6) has better balance, resulting in lower A/D distortion. 50Ω VCM 0.1μF 0.1μF 50Ω VCM 0.1μF 0.1μF ANALOG INPUT T1 1:1 25Ω 25Ω 25Ω 0.1μF AIN+ LTC2259-16 12pF ANALOG INPUT T2 T1 25Ω 25Ω 0.1μF AIN+ LTC2259-16 4.7pF 0.1μF AIN– 225916 F04 25Ω AIN– 225916 F03 T1: MA/COM MABAES0060 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE T1: MA/COM MABA-007159-000000 T2: MA/COM MABAES0060 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE Figure 3. Analog Input Circuit Using a Transformer. Recommended for Input Frequencies from 5MHz to 70MHz Figure 4. Recommended Front-End Circuit for Input Frequencies from 70MHz to 170MHz 50Ω VCM 0.1μF 50Ω VCM 0.1μF 0.1μF ANALOG INPUT T2 T1 25Ω 25Ω 0.1μF AIN+ LTC2259-16 1.8pF 0.1μF ANALOG INPUT 25Ω T1 0.1μF 25Ω 2.7nH 0.1μF AIN+ LTC2259-16 0.1μF AIN– 225916 F05 2.7nH AIN– 225916 F06 T1: MA/COM MABA-007159-000000 T2: COILCRAFT WBC1-1LB RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE T1: MA/COM ETC1-1-13 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE Figure 5. Recommended Front-End Circuit for Input Frequencies from 170MHz to 270MHz Figure 6. Recommended Front-End Circuit for Input Frequencies Above 270MHz 225916f 14 LTC2259-16 APPLICATIONS INFORMATION Amplifier Circuits Figure 7 shows the analog input being driven by a high speed differential amplifier. The output of the amplifier is AC-coupled to the A/D so the amplifier’s output common mode voltage can be optimally set to minimize distortion. At very high frequencies an RF gain block will often have lower distortion than a differential amplifier. If the gain block is single-ended, then a transformer circuit (Figures 4 to 6) should convert the signal to differential before driving the A/D. Reference The LTC2259-16 has an internal 1.25V voltage reference. For a 2V input range using the internal reference, connect SENSE to VDD. For a 1V input range using the internal reference, connect SENSE to ground. For a 2V input range with an external reference, apply a 1.25V reference voltage to SENSE (Figure 9.) The input range can be adjusted by applying a voltage to SENSE that is between 0.625V and 1.30V. The input range will then be 1.6 • VSENSE. The VREF , REFH and REFL pins should be bypassed as shown in Figure 8. The 0.1μF capacitor between REFH and REFL should be as close to the pins as possible (not on the back side of the circuit board). VCM HIGH SPEED DIFFERENTIAL 0.1μF AMPLIFIER ANALOG INPUT 200Ω 200Ω 25Ω 0.1μF AIN+ LTC2259-16 2.2μF 0.1μF 0.8x DIFF AMP 1.25V VREF 1μF 0.625V RANGE DETECT AND CONTROL SENSE BUFFER INTERNAL ADC HIGH REFERENCE REFH LTC2259-16 5Ω 1.25V BANDGAP REFERENCE TIE TO VDD FOR 2V RANGE; TIE TO GND FOR 1V RANGE; RANGE = 1.6 • VSENSE FOR 0.65V < VSENSE < 1.300V 0.1μF 0.1μF REFL INTERNAL ADC LOW REFERENCE 225916 F08 Figure 8. Reference Circuit VREF 1μF LTC2259-16 1.25V EXTERNAL REFERENCE SENSE 1μF 225916 F09 Figure 9. Using an External 1.25V Reference + – + 12pF – 0.1μF 25Ω AIN– 225916 F07 Figure 7. Front-End Circuit Using a High Speed Differential Amplifier 225916f 15 LTC2259-16 APPLICATIONS INFORMATION Encode Input The signal quality of the encode inputs strongly affects the A/D noise performance. The encode inputs should be treated as analog signals—do not route them next to digital traces on the circuit board. There are two modes of operation for the encode inputs: the differential encode mode (Figure 10) and the single-ended encode mode (Figure 11). The differential encode mode is recommended for sinusoidal, PECL or LVDS encode inputs (Figures 12, 13). The encode inputs are internally biased to 1.2V through 10k equivalent resistance. The encode inputs can be taken above VDD (up to 3.6V), and the common mode range is from 1.1V to 1.6V. In the differential encode mode, ENC– should stay at least 200mV above ground to avoid falsely triggering the single-ended encode mode. For good jitter performance ENC+ and ENC– should have fast rise and fall times. LTC2259-16 VDD DIFFERENTIAL COMPARATOR 25Ω 0.1μF T1 1:4 ENC+ 100Ω LTC2259-16 100Ω ENC– 0.1μF 225916 F12 The single-ended encode mode should be used with CMOS encode inputs. To select this mode, ENC– is connected to ground and ENC+ is driven with a square wave encode input. ENC+ can be taken above VDD (up to 3.6V) so 1.8V to 3.3V CMOS logic levels can be used. The ENC+ threshold is 0.9V. For good jitter performance ENC+ should have fast rise and fall times. Clock Duty Cycle Stabilizer For good performance the encode signal should have a 50%(±5%) duty cycle. If the optional clock duty cycle stabilizer circuit is enabled, the encode duty cycle can vary from 30% to 70% and the duty cycle stabilizer will maintain a constant 50% internal duty cycle. If the encode signal changes frequency or is turned off, the duty cycle stabilizer circuit requires one hundred clock cycles to lock onto the input clock. The duty cycle stabilizer is enabled by mode control register A2 (serial programming mode), or by CS (parallel programming mode). VDD D1 15k ENC+ ENC– 30k T1: COILCRAFT WBC4 - 1WL D1: AVAGO HSMS - 2822 RESISTORS, CAPACITORS ARE 0402 PACKAGE SIZE 225916 F10 Figure 10. Equivalent Encode Input Circuit for Differential Encode Mode Figure 12. Sinusoidal Encode Drive LTC2259-16 1.8V TO 3.3V 0V ENC+ ENC– 30k CMOS LOGIC BUFFER 225916 F11 0.1μF ENC+ PECL OR LVDS CLOCK LTC2259-16 0.1μF ENC– 225916 F13 Figure 11. Equivalent Encode Input Circuit for Single-Ended Encode Mode Figure 13. PECL or LVDS Encode Drive 225916f 16 LTC2259-16 APPLICATIONS INFORMATION For applications where the sample rate needs to be changed quickly, the clock duty cycle stabilizer can be disabled. If the duty cycle stabilizer is disabled, care should be taken to make the sampling clock have a 50%(±5%) duty cycle. The duty cycle stabilizer should not be used below 5Msps. DIGITAL OUTPUTS Digital Output Modes The LTC2259-16 can operate in three digital output modes: full-rate CMOS, double-data rate CMOS (to halve the number of output lines), or double-data rate LVDS (to reduce digital noise in the system). The output mode is set by mode control register A3 (serial programming mode), or by SCK (parallel programming mode). Note that double-data rate CMOS cannot be selected in the parallel programming mode. Full-Rate CMOS Mode In full-rate CMOS mode the 16 digital outputs (D0-D15), and the data output clocks (CLKOUT+, CLKOUT–) have CMOS output levels. The outputs are powered by OVDD and OGND which are isolated from the A/D core power and ground. OVDD can range from 1.1V to 1.9V, allowing 1.2V through 1.8V CMOS logic outputs. For good performance, the digital outputs should drive minimal capacitive loads. If the load capacitance is larger than 10pF a digital buffer should be used. Double-Data Rate CMOS Mode In double-data rate CMOS mode, two data bits are multiplexed and output on each data pin. This reduces the number of data lines by eight, simplifying board routing and reducing the number of input pins needed to receive the data. The 8 digital outputs (D0_1, D2_3, D4_5, D6_7, D8_9, D10_11, D12_13, D14_15), and the data output clocks (CLKOUT+, CLKOUT–) have CMOS output levels. The outputs are powered by OVDD and OGND which are isolated from the A/D core power and ground. OVDD can range from 1.1V to 1.9V, allowing 1.2V through 1.8V CMOS logic outputs. For good performance the digital outputs should drive minimal capacitive loads. If the load capacitance is larger than 10pF a digital buffer should be used. Double-Data Rate LVDS Mode In double-data rate LVDS mode, two data bits are multiplexed and output on each differential output pair. There are 8 LVDS output pairs (D0_1+/D0_1– through D14_15+/ D14_15–) for the digital output data. The data output clock (CLKOUT+/CLKOUT–) has an LVDS output pair. By default the outputs are standard LVDS levels: 3.5mA output current and a 1.25V output common mode voltage. An external 100Ω differential termination resistor is required for each LVDS output pair. The termination resistors should be located as close as possible to the LVDS receiver. The outputs are powered by OVDD and OGND which are isolated from the A/D core power and ground. In LVDS mode, OVDD must be 1.8V. Programmable LVDS Output Current In LVDS mode, the default output driver current is 3.5mA. This current can be adjusted by serially programming mode control register A3. Available current levels are 1.75mA, 2.1mA, 2.5mA, 3mA, 3.5mA, 4mA and 4.5mA. Optional LVDS Driver Internal Termination In most cases using just an external 100Ω termination resistor will give excellent LVDS signal integrity. In addition, an optional internal 100Ω termination resistor can be enabled by serially programming mode control register A3. The internal termination helps absorb any reflections caused by imperfect termination at the receiver. When the internal termination is enabled, the output driver current is increased by 1.6x to maintain about the same output voltage swing. 225916f 17 LTC2259-16 APPLICATIONS INFORMATION Phase-Shifting the Output Clock In full-rate CMOS mode the data output bits normally change at the same time as the falling edge of CLKOUT+, so the rising edge of CLKOUT+ can be used to latch the output data. In double-data rate CMOS and LVDS modes the data output bits normally change at the same time as the falling and rising edges of CLKOUT+. To allow adequate setup-and-hold time when latching the data, the CLKOUT+ signal may need to be phase shifted relative to the data output bits. Most FPGAs have this feature; this is generally the best place to adjust the timing. The LTC2259-16 can also phase shift the CLKOUT+/CLKOUT– signals by serially programming mode control register A2. The output clock can be shifted by 0°, 45°, 90° or 135°. To use the phase shifting feature the clock duty cycle stabilizer must be turned on. Another control register bit can invert the polarity of CLKOUT+ and CLKOUT–, independently of the phase shift. The combination of these two features enables phase shifts of 45° up to 315° (Figure 14). DATA FORMAT Table 1 shows the relationship between the analog input voltage and the digital data output bits. By default the output data format is offset binary. The 2’s complement format can be selected by serially programming mode control register A4. Note that when the analog input is outside the normal operating range the two LSBs (D1, D0) can change and should be ignored. Table 1. Output Codes vs Input Voltage AIN+ – AIN– (2V Range) >1.000000V +0.999970V +0.999939V +0.999909V +0.999978V +0.000030V +0.000000V +0.000030V +0.000061V –0.999878V –0.999909V –0.999939V –1.000000V < –1.000000V D15-D0 (OFFSET BINARY) 1111 1111 1111 11XX 1111 1111 1111 1111 1111 1111 1111 1110 1111 1111 1111 1101 1111 1111 1111 1100 1000 0000 0000 0001 1000 0000 0000 0000 0111 1111 1111 1111 0111 1111 1111 1110 0000 0000 0000 0011 0000 0000 0000 0010 0000 0000 0000 0001 0000 0000 0000 0000 0000 0000 0000 00XX D15-D0 (2’s COMPLEMENT) 0111 1111 1111 11XX 0111 1111 1111 1111 0111 1111 1111 1110 0111 1111 1111 1101 0111 1111 1111 1100 0000 0000 0000 0001 0000 0000 0000 0000 1111 1111 1111 1111 1111 1111 1111 1110 1000 0000 0000 0011 1000 0000 0000 0010 1000 0000 0000 0001 1000 0000 0000 0000 1000 0000 0000 00XX Note: X means data could be 1 or 0. ENC+ D0-D13, OF PHASE SHIFT 0° 45° 90° 135° CLKOUT+ 180° 225° 270° 315° 225916 F14 MODE CONTROL BITS CLKINV 0 0 0 0 1 1 1 1 CLKPHASE1 0 0 1 1 0 0 1 1 CLKPHASE0 0 1 0 1 0 1 0 1 Figure 14. Phase-Shifting CLKOUT 225916f 18 LTC2259-16 APPLICATIONS INFORMATION Digital Output Randomizer Interference from the A/D digital outputs is sometimes unavoidable. Digital interference may be from capacitive or inductive coupling or coupling through the ground plane. Even a tiny coupling factor can cause unwanted tones in the ADC output spectrum. By randomizing the digital output before it is transmitted off chip, these unwanted tones can be randomized which reduces the unwanted tone amplitude. The digital output is randomized by applying an exclusiveOR logic operation between D2 and all other data output bits. To decode, the reverse operation is applied—an exclusive-OR operation is applied between D2 and all other bits. The D2 and CLKOUT outputs are not affected. The output randomizer is enabled by serially programming mode control register A4. Alternate Bit Polarity Another feature that reduces digital feedback on the circuit board is the alternate bit polarity mode. When this mode is enabled, all of the odd bits (D1, D3, D5, D7, D9, D11, D13, D15) are inverted before the output buffers. The even bits (D0, D2, D4, D6, D8, D10, D12, D14) and CLKOUT are not affected. This can reduce digital currents in the circuit board ground plane and reduce digital noise, particularly for very small analog input signals. When there is a very small signal at the input of the A/D that is centered around mid-scale, the digital outputs toggle between mostly 1s and mostly 0s. This simultaneous switching of most of the bits will cause large currents in the ground plane. By inverting every other bit, the alternate bit polarity mode makes half of the bits transition high while half of the bits transition low. To first order, this cancels current flow in the ground plane, reducing the digital noise. PC BOARD CLKOUT FPGA D15 D15 D2 D15 D2 D15 D14 D14 D2 D14 D2 CLKOUT CLKOUT • • • D3 • • • D3 D2 LTC2259-16 • • • D3 D2 D14 • • • D3 D2 D1 D2 D2 D1 D2 D1 D2 D2 D1 D0 RANDOMIZER ON D2 225916 F15 D0 D2 D0 D2 D0 225916 F16 Figure 15. Functional Equivalent of Digital Output Randomizer Figure 16. De-Randomizing a Randomized Digital Output Signal 225916f 19 LTC2259-16 APPLICATIONS INFORMATION The digital output is decoded at the receiver by inverting the odd bits (D1, D3, D5, D7, D9, D11, D13, D15). The alternate bit polarity mode is independent of the digital output randomizer—either, both or neither function can be on at the same time. When alternate bit polarity mode is on, the data format is offset binary and the 2’s complement control bit has no effect. The alternate bit polarity mode is enabled by serially programming mode control register A4. Digital Output Test Patterns To allow in-circuit testing of the digital interface to the A/D, there are several test modes that force most of the A/D data outputs (D15-D2) to known values. Note that the two LSBs, D1 and D0, are not controlled in the test pattern mode and can have unknown values. All 1s: Outputs are 1111 1111 1111 11XX All 0s: Outputs are 0000 0000 0000 00XX Alternating: On alternating samples, the outputs change from 1111 1111 1111 11XX to 0000 0000 0000 00XX. Checkerboard: On alternating samples, the outputs change from 1010 1010 1010 10XX to 0101 0101 0101 01XX. The digital output test patterns are enabled by serially programming mode control register A4. When enabled, the test patterns override all other formatting modes: 2’s complement, randomizer, alternate-bit-polarity. Output Disable The digital outputs may be disabled by serially programming mode control register A3. All digital outputs including CLKOUT are disabled. The high impedance disabled state is intended for long periods of inactivity—it is too slow to multiplex a data bus between multiple converters at full speed. Sleep and Nap Modes The A/D may be placed in sleep or nap modes to conserve power. In sleep mode the entire A/D converter is powered down, resulting in 0.5mW power consumption. Sleep mode is enabled by mode control register A1 (serial programSDI ming mode), or by SDI (parallel programming mode). The amount of time required to recover from sleep mode depends on the size of the bypass capacitors on VREF , REFH, and REFL. For the suggested values in Figure 8, the A/D will stabilize after 2ms. In nap mode the A/D core is powered down while the internal reference circuits stay active, allowing faster wake-up than from sleep mode. Recovering from nap mode requires at least 100 clock cycles. If the application demands very accurate DC settling then an additional 50μs should be allowed so the on-chip references can settle from the slight temperature shift caused by the change in supply current as the A/D leaves nap mode. Nap mode is enabled by mode control register A1 in the serial programming mode. DEVICE PROGRAMMING MODES The operating modes of the LTC2259-16 can be programmed by either a parallel interface or a simple serial interface. The serial interface has more flexibility and can program all available modes. The parallel interface is more limited and can only program some of the more commonly used modes. Parallel Programming Mode To use the parallel programming mode, PAR/SER should be tied to VDD. The CS, SCK and SDI pins are binary logic inputs that set certain operating modes. These pins can be tied to VDD or ground, or driven by 1.8V, 2.5V or 3.3V CMOS logic. Table 2 shows the modes set by CS, SCK and SDI. Table 2. Parallel Programming Mode Control Bits (PAR/SER = VDD) PIN CS DESCRIPTION Clock Duty Cycle Stabilizer Control Bit 0 = Clock Duty Cycle Stabilizer Off 1 = Clock Duty Cycle Stabilizer On SCK Digital Output Mode Control Bit 0 = Full-Rate CMOS Output Mode 1 = Double-Data Rate LVDS Output Mode (3.5mA LVDS Current, Internal Termination Off) Power Down Control Bit 0 = Normal Operation 1 = Sleep Mode 225916f 20 LTC2259-16 APPLICATIONS INFORMATION Serial Programming Mode To use the serial programming mode, PAR/SER should be tied to ground. The CS, SCK, SDI and SDO pins become a serial interface that program the A/D mode control registers. Data is written to a register with a 16-bit serial word. Data can also be read back from a register to verify its contents. Serial data transfer starts when CS is taken low. The data on the SDI pin is latched at the first 16 rising edges of SCK. Any SCK rising edges after the first 16 are ignored. The data transfer ends when CS is taken high again. The first bit of the 16-bit input word is the R/W bit. The next seven bits are the address of the register (A6:A0). The final eight bits are the register data (D7:D0). If the R/W bit is low, the serial data (D7:D0) will be written to the register set by the address bits (A6:A0). If the R/W bit is high, data in the register set by the address bits (A6:A0) will be read back on the SDO pin (see the timing Table 3. Serial Programming Mode Register Map REGISTER A0: RESET REGISTER (ADDRESS 00h) D7 RESET Bit 7 RESET D6 X D5 X Software Reset Bit D4 X D3 X D2 X D1 X D0 X diagrams). During a read back command the register is not updated and data on SDI is ignored. The SDO pin is an open-drain output that pulls to ground with a 200Ω impedance. If register data is read back through SDO, an external 2k pull-up resistor is required. If serial data is only written and read back is not needed, then SDO can be left floating and no pull-up resistor is needed. Table 3 shows a map of the mode control registers. Software Reset If serial programming is used, the mode control registers should be programmed as soon as possible after the power supplies turn on and are stable. The first serial command must be a software reset which will reset all register data bits to logic 0. To perform a software reset, bit D7 in the reset register is written with a logic 1. After the reset is complete, bit D7 is automatically set back to zero. 0 = Not Used 1 = Software Reset. All mode control registers are reset to 00h. This bit is automatically set back to zero after the reset is complete. Bits 6-0 Unused, Don’t Care Bits. REGISTER A1: POWER-DOWN REGISTER (ADDRESS 01h) D7 X Bits 7-2 Bits 1-0 D6 X Unused, Don’t Care Bits. PWROFF1:PWROFF0 00 = Normal Operation 01 = Nap Mode 10 = Not Used 11 = Sleep Mode Power-Down Control Bits D5 X D4 X D3 X D2 X D1 PWROFF1 D0 PWROFF0 225916f 21 LTC2259-16 APPLICATIONS INFORMATION REGISTER A2: TIMING REGISTER (ADDRESS 02h) D7 X Bits 7-4 Bit 3 D6 X Unused, Don’t Care Bits. CLKINV Output Clock Invert Bit 0 = Normal CLKOUT Polarity (as shown in the timing diagrams) 1 = Inverted CLKOUT Polarity CLKPHASE1:CLKPHASE0 Output Clock Phase Delay Bits 00 = No CLKOUT Delay (as shown in the timing diagrams) 01 = CLKOUT+/CLKOUT– Delayed by 45° (Clock Period • 1/8) 10 = CLKOUT+/CLKOUT– Delayed by 90° (Clock Period • 1/4) 11 = CLKOUT+/CLKOUT– Delayed by 135° (Clock Period • 3/8) Note: If the CLKOUT phase delay feature is used, the clock duty cycle stabilizer must also be turned on. DCS Clock Duty Cycle Stabilizer Bit 0 = Clock Duty Cycle Stabilizer Off 1 = Clock Duty Cycle Stabilizer On D5 X D4 X D3 CLKINV D2 CLKPHASE1 D1 CLKPHASE0 D0 DCS Bits 2-1 Bit 0 REGISTER A3: OUTPUT MODE REGISTER (ADDRESS 03h) D7 X Bit 7 Bits 6-4 D6 ILVDS2 Unused, Don’t Care Bit. ILVDS2:ILVDS0 LVDS Output Current Bits 000 = 3.5mA LVDS Output Driver Current 001 = 4.0mA LVDS Output Driver Current 010 = 4.5mA LVDS Output Driver Current 011 = Not Used 100 = 3.0mA LVDS Output Driver Current 101 = 2.5mA LVDS Output Driver Current 110 = 2.1mA LVDS Output Driver Current 111 = 1.75mA LVDS Output Driver Current TERMON LVDS Internal Termination Bit 0 = Internal Termination Off 1 = Internal Termination On. LVDS output driver current is 1.6× the current set by ILVDS2:ILVDS0. OUTOFF Output Disable Bit 0 = Digital Outputs are enabled. 1 = Digital Outputs are disabled and have high output impedance. OUTMODE1:OUTMODE0 Digital Output Mode Control Bits 00 = Full-Rate CMOS Output Mode 01 = Double-Data Rate LVDS Output Mode 10 = Double-Data Rate CMOS Output Mode 11 = Not Used D5 ILVDS1 D4 ILVDS0 D3 TERMON D2 OUTOFF D1 OUTMODE1 D0 OUTMODE0 Bit 3 Bit 2 Bits 1-0 225916f 22 LTC2259-16 APPLICATIONS INFORMATION REGISTER A4: DATA FORMAT REGISTER (ADDRESS 04h) D7 X Bit 7-6 Bits 5-3 D6 X Unused, Don’t Care Bits. OUTTEST2:OUTTEST0 Digital Output Test Pattern Bits 000 = Digital Output Test Patterns Off 001 = Digital Outputs = 0000 0000 0000 00XX 011 = Digital Outputs = 1111 1111 1111 11XX 101 = Checkerboard Output Pattern. D15-D0 alternate between 0101 0101 0101 01XX and 1010 1010 1010 10XX. 111 = Alternating Output Pattern. D15-D0 alternate between 0000 0000 0000 00XX and 1111 1111 1111 11XX. Note: Other bit combinations are not used. D1 and D0 are not controlled by the digital output test patterns. ABP Alternate Bit Polarity Mode Control Bit 0 = Alternate Bit Polarity Mode Off 1 = Alternate Bit Polarity Mode On RAND Data Output Randomizer Mode Control Bit 0 = Data Output Randomizer Mode Off 1 = Data Output Randomizer Mode On TWOSCOMP Two’s Complement Mode Control Bit 0 = Offset Binary Data Format 1 = Two’s Complement Data Format Note: ABP = 1 forces the output format to be offset binary. D5 OUTTEST2 D4 OUTTEST1 D3 OUTTEST0 D2 ABP D1 RAND D0 TWOSCOMP Bit 2 Bit 1 Bit 0 GROUNDING AND BYPASSING The LTC2259-16 requires a printed circuit board with a clean unbroken ground plane. A multilayer board with an internal ground plane in the first layer beneath the ADC is recommended. Layout for the printed circuit board should ensure that digital and analog signal lines are separated as much as possible. In particular, care should be taken not to run any digital track alongside an analog signal track or underneath the ADC. High quality ceramic bypass capacitors should be used at the VDD, OVDD, VCM, VREF, REFH and REFL pins. Bypass capacitors must be located as close to the pins as possible. Of particular importance is the 0.1μF capacitor between REFH and REFL. This capacitor should be on the same side of the circuit board as the A/D, and as close to the device as possible (1.5mm or less). Size 0402 ceramic capacitors are recommended. The larger 2.2μF capacitor between REFH and REFL can be somewhat further away. The VCM capacitor should be located as close to the pin as possible. To make space for this the capacitor on VREF can be further away or on the back of the PC board. The traces connecting the pins and bypass capacitors must be kept short and should be made as wide as possible. The analog inputs, encode signals, and digital outputs should not be routed next to each other. Ground fill and grounded vias should be used as barriers to isolate these signals from each other. HEAT TRANSFER Most of the heat generated by the LTC2259-16 is transferred from the die through the bottom-side exposed pad and package leads onto the printed circuit board. For good electrical and thermal performance, the exposed pad must be soldered to a large grounded pad on the PC board. This pad should be connected to the internal ground planes by an array of vias. 225916f 23 LTC2259-16 TYPICAL APPLICATIONS LTC2259-16 Schematic T2 MABAES0060 R9 10Ω R39 33.2Ω 1% R40 33.2Ω 1% SENSE C23 1μF • ANALOG INPUT • C51 4.7pF C17 1μF R14 1k R10 10Ω R15 100Ω C12 0.1μF C13 1μF C19 0.1μF 40 39 38 37 36 D1 35 D0 34 33 32 31 VDD SENSE VREF VCM R27 10Ω 1 R28 10Ω 2 3 4 C15 0.1μF 5 C20 2.2μF 6 7 C21 0.1μF PAR/SER 8 9 10 C18 0.1μF AIN+ AIN– GND REFH REFH REFL REFL PAR/SER VDD VDD GND 41 ENC+ ENC– 11 12 CS 13 SCK 14 SDI SDO 15 16 D2 17 D3 18 D4 19 LTC2259-16 D15 D14 D13 D12 30 29 28 27 26 25 24 23 22 21 DIGITAL OUTPUTS D11 D10 CLKOUT+ CLKOUT– OVDD OGND D9 D8 D7 D6 D5 20 0VDD C37 0.1μF DIGITAL OUTPUTS ENCODE CLOCK R13 100Ω 225916 TA02 SPI BUS 225916f 24 LTC2259-16 TYPICAL APPLICATIONS Silkscreen Top Top Side 225916 TA04 225916 TA03 Inner Layer 2 GND Inner Layer 3 225916 TA04 225916 TA06 225916f 25 LTC2259-16 TYPICAL APPLICATIONS Inner Layer 4 Inner Layer 5 Power 225916 TA07 225916 TA08 Bottom Side 225916 TA09 225916f 26 LTC2259-16 PACKAGE DESCRIPTION UJ Package 40-Lead Plastic QFN (6mm × 6mm) (Reference LTC DWG # 05-08-1728 Rev Ø) 0.70 ±0.05 6.50 ±0.05 5.10 ±0.05 4.42 ±0.05 4.50 ±0.05 (4 SIDES) 4.42 ±0.05 PACKAGE OUTLINE 0.25 ±0.05 0.50 BSC RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS APPLY SOLDER MASK TO AREAS THAT ARE NOT SOLDERED 6.00 ± 0.10 (4 SIDES) 0.75 ± 0.05 R = 0.10 TYP R = 0.115 TYP 39 40 0.40 ± 0.10 1 PIN 1 NOTCH R = 0.45 OR 0.35 45° CHAMFER 2 PIN 1 TOP MARK (SEE NOTE 6) 4.50 REF (4-SIDES) 4.42 ±0.10 4.42 ±0.10 (UJ40) QFN REV Ø 0406 0.200 REF 0.00 – 0.05 NOTE: 1. DRAWING IS A JEDEC PACKAGE OUTLINE VARIATION OF (WJJD-2) 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.20mm ON ANY SIDE, IF PRESENT 5. EXPOSED PAD SHALL BE SOLDER PLATED 6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION ON THE TOP AND BOTTOM OF PACKAGE 0.25 ± 0.05 0.50 BSC BOTTOM VIEW—EXPOSED PAD 225916f Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 27 LTC2259-16 TYPICAL APPLICATION T2 MABAES0060 R9 10Ω R39 33.2Ω 1% R40 33.2Ω 1% SENSE • ANALOG INPUT • C23 1μF C51 4.7pF C17 1μF R14 1k R10 10Ω R15 100Ω C12 0.1μF C13 1μF C19 0.1μF 40 39 38 37 36 D1 35 D0 34 33 32 31 VDD SENSE VREF VCM R27 10Ω 1 R28 10Ω 2 3 4 C15 0.1μF 5 C20 2.2μF 6 7 C21 0.1μF PAR/SER 8 9 10 C18 0.1μF AIN+ AIN– GND REFH REFH REFL REFL PAR/SER VDD VDD GND 41 ENC+ ENC– 11 12 CS 13 SCK 14 SDI SDO 15 16 D2 17 D3 18 D4 19 LTC2259-16 D15 D14 D13 D12 30 29 28 27 26 25 24 23 22 21 DIGITAL OUTPUTS D11 D10 CLKOUT+ CLKOUT– OVDD OGND D9 D8 D7 D6 D5 20 0VDD C37 0.1μF DIGITAL OUTPUTS ENCODE CLOCK R13 100Ω 225916 TA10 SPI BUS RELATED PARTS PART NUMBER LTC1993-2 LTC1994 LTC6406 LTC2259-14/ LTC2260-14/ LTC2261-14 LTC2259-12/ LTC2260-12/ LTC2261-12 DESCRIPTION High Speed Differential Op-Amp/ADC Driver Low Noise, Low Distortion Fully Differential Input/Output Amplifier/Driver 3GHz, Low Noise, Rail-to-Rail Input Differential Amplifier/Driver 14-Bit, 80Msps/105Msps/125Msps Ultralow Power 1.8V ADCs COMMENTS 800MHz 70dBc Distortion at 70MHz, 6dB Gain Low Distortion: –94dBc at 1MHz Low Noise: 1.6nV/√Hz RTI 89mW/106mW/127mW, 73.4dB SNR, 85dB SFDR, DDR LVDS/DDR CMOS/CMOS Outputs, 6mm × 6mm QFN Package 87mW/103mW/124mW, 70.8dB SNR, 85dB SFDR, DDR LVDS/DDR CMOS/CMOS Outputs, 6mm × 6mm QFN Package 225916f 12-Bit, 80Msps/105Msps/125Msps Ultralow Power 1.8V ADCs 28 Linear Technology Corporation (408) 432-1900 ● FAX: (408) 434-0507 ● LT 0310 • PRINTED IN USA 1630 McCarthy Blvd., Milpitas, CA 95035-7417 www.linear.com © LINEAR TECHNOLOGY CORPORATION 2010