ADN2870 Analog Devices, Inc., ADN2870 Datasheet
ADN2870
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ADN2870 Summary of contents
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... V Dual-Loop, 50 Mbps to 3.3 Gbps GENERAL DESCRIPTION The ADN2870 laser diode driver is designed for advanced SFP and SFF modules, using SFF-8472 digital diagnostics. The device features dual-loop control of the average power and extinction ratio, which automatically compensates for variations in laser characteristics over temperature and aging. The laser need only be calibrated at 25° ...
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... ADN2870 TABLE OF CONTENTS Specifications..................................................................................... 3 SFP Timing Specifications............................................................... 5 Absolute Maximum Ratings............................................................ 6 ESD Caution.................................................................................. 6 Pin Configuration and Function Descriptions............................. 7 Typical Operating Characteristics.................................................. 8 Optical Waveforms Showing Multirate Performance Using Low Cost Fabry Perot Tosa NEC NX7315UA .......................... 8 Optical Waveforms Showing Dual-Loop Performance Over Temperature Using DFB Tosa SUMITOMO SLT2486............ 8 Performance Characteristics ...
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... Voltage setpoint mode (RPAV fixed at 1 kΩ Voltage setpoint mode (RERSET fixed at 1 kΩ) 2.4 V AC-coupled Ω Voltage required at FAIL for Ibias and Imod to turn off when FAIL asserted V Voltage required at FAIL for Ibias and Imod to stay on when FAIL asserted ADN2870 ...
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... Typ Max 85 100 115 92 100 108 ± 3.0 3.3 3 ADN2870 R L 22Ω TO HIGH SPEED C DIGITAL IMODP OSCILLOSCOPE 50Ω INPUT BIAS TEE 80kHz → 27GHz Figure 2. High Speed Electrical Test Output Circuit Rev Page Unit Conditions/Comments A < IBIAS < A < IBIAS < 100 < ...
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... From power-on or negation of FAIL using ALS. 100 µs Time to fault to FAIL on. 5 µs Time TX_DISABLE must be held high to reset TX_FAULT. × Rev Page SFP MODULE 1µH VCC_Tx 0.1µF 0.1µF 10µF SFP HOST BOARD Figure 4. Recommended SFP Supply ADN2870 3.3V ...
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... ADN2870 ABSOLUTE MAXIMUM RATINGS T = 25°C, unless otherwise noted. A Table 3. Parameter VCC to GND IMODN, IMODP PAVCAP ERCAP PAVSET PAVREF ERREF IBIAS IBMON IMMON ALS CCBIAS RPAV ERSET FAIL DATAP, DATAN (single-ended differential) TEMPERATURE SPECIFICATIONS Operating Temperature Range Industrial Storage Temperature Range ...
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... Bias Current Monitor Current Source FAIL Alarm Output Supply Ground Supply Voltage Modulation Current Positive Output, Connect to Laser Diode Modulation Current Negative Output Supply Ground Laser Diode Bias (Current Sink to Ground) Rev Page ALS DATAN DATAP GND PAVCAP ERCAP 7 6 ADN2870 ...
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... ADN2870 TYPICAL OPERATING CHARACTERISTICS V = 3.3 V and T = 25°C, unless otherwise noted OPTICAL WAVEFORMS SHOWING MULTIRATE PERFORMANCE USING LOW COST FABRY PEROT TOSA NEC NX7315UA Note: No change to PAVCAP and ERCAP values (ACQ LIMIT TEST) WAVEFORMS 1000 Figure 6. Optical Eye 2.488 Gbps,65 ps/div, PRBS 2 PAV = − ...
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... Figure 15. Total Supply Current vs. Modulation Current 100 –50 Figure 16. Supply Current (I Rev Page ADN2870 MODULATION CURRENT (mA 80mA BIAS I = 40mA BIAS I = 20mA BIAS MODULATION CURRENT (mA) Total Supply Current = I ...
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... ADN2870 120 115 110 105 100 –50 –30 – TEMPERATURE (°C) Figure 17. IBIAS/IBMON Gain vs. Temperature, Ibias = 20 mA OC48 PRBS31 DATA TRANSMISSION t _OFF ALS Figure 18. ALS Assert Time, 5 µs/div OC48 PRBS31 DATA TRANSMISSION t _ON ALS Figure 19. ALS Negate Time, 200 µs/div ...
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... Dual Loop The ADN2870 uses a proprietary patented method to control both average power and extinction ratio. The ADN2870 is constantly sending a test signal on the modulation current signal and reading the resulting change in the MPD current as a means of detecting the slope of the laser in real time. This ...
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... Some types of laser have LI curves that become progressively more nonlinear with increasing temperature (see Figure 25). At temperatures where the LI curve shows significant nonlinearity, the LI curve slope measured by the ADN2870 at the optical 1 level is no longer representative of the overall LI curve evident that applying a modulation current based on this slope information cannot maintain a constant extinction ratio over temperature ...
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... Figure 26. ADN2870 Using Microconverter Calibration and Monitoring VCC VCC VCC PAVREF MPD RPAV PAVSET GND ERSET GND VCC ERREF VCC GND Figure 27. ADN2870 Using Resistor Setpoint Calibration of Average Power and Energy Ratio VCC VCC FAIL ALS IMODN IMOD CONTROL IBIAS ADN2870 IBMON IMMON PAVCAP VCC GND GND 1kΩ ...
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... PAVSET and ERSET pins, respectively. A resistor is placed between the pin and GND to set the current flowing in each pin as shown in Figure 27. The ADN2870 ensures that both PAVSET and ERSET are kept 1.2 V above GND. The PAVSET and ERSET resistors are given by the following: ...
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... POWER CONSUMPTION The ADN2870 die temperature must be kept below 125°C. The LFCSP package has an exposed paddle, which should be con- nected such that is at the same potential as the ADN2870 ground pins. Power consumption can be calculated as follows: Thus, the maximum combination of I calculated. ...
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... ADN2870 LASER DIODE INTERFACING The schematic in Figure 32 describes the recommended circuit for interfacing the ADN2870 to most TO-Can or Coax lasers. These lasers typically have impedances of 5 Ω Ω, and have axial leads. The circuit shown works over the full range of data rates from 155 Mbps to 3.3 Gbps including multirate operation (with no change to PAVCAP and ERCAP values) ...
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... Alarm Type Pin Name 1. Bias Current IBMON 2. MPD Current PAVSET 3. Crucial Nodes ERREF IBIAS Table 6. ADN2870 Response to Various Single-Point Faults in AC-Coupled Configuration as Shown in Figure 32 Pin Short to VCC CCBIAS Fault state occurs PAVSET Fault state occurs PAVREF Voltage mode: Fault state occurs ...
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... PLANE Note: The LFCSP package has an exposed paddle that must be connected to ground. ORDERING GUIDE Model Temperature Range ADN2870ACPZ 1 −40°C to +85°C 1 ADN2870ACPZ-RL −40°C to +85°C 1 ADN2870ACPZ-RL7 −40°C to +85° Pb-free part. 4.00 BSC SQ 0.60 MAX 0.50 BSC TOP 3.75 VIEW BSC SQ ...
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... Preliminary Technical Data NOTES Rev Page ADN2870 ...
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... ADN2870 NOTES © 2004 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D04510–0–8/04(0) Rev Page ...