MAX3738 DS Rev2.C

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1 ; Rev 2; 12/08 可提供评估板 155Mbps 至 4.25Gbps SFF/SFP 激光器驱动器, 概述为 +3.3V 激光驱动器, 专为数据速率从 155Mbps 至 4.25Gbps 的多速率收发模块而设计激光器直流耦合到, 减少了外部元件数量, 易于多速率运行激光器消光比控制 (ERC) 包括自动功率控制 (APC) 调制补偿和片内温度补偿等 APC 环路保持平均光功率恒定 ; 调制补偿根据偏置电流调节调制电流这些控制环路具有温度补偿, 在整个温度范围和有效使用期限内保持恒定的消光比接受差分数据输入信号 5mA 至 60mA ( 交流耦合时高达 85mA) 的宽调制电流范围和高达 100mA 的偏置电流范围, 使尤其适合于驱动光模块中的 FP/DFB 激光器外部电阻设置所需的激光器电流值提供发送禁止控制 () 单点故障容限偏置电流监视及光电流监视该器件还提供一个锁定的失效输出 (TX_FAULT), 用于指示故障, 例如 APC 回路无法保持期望的平均光功率时符合 SFF-8472 发送器诊断及 SFP MSA 的定时要求提供 24 引脚 4mm x 4mm 薄型 QFN 封装, 工作在 -40 C 至 +85 C 的扩展级温度范围内特性 +3.3V 单电源供电 47mA 电源电流 85mA 调制电流 100mA 偏置电流自动功率控制 (APC) 调制补偿片内温度补偿用于交流耦合的自偏置输入以地为参考的电流监测激光器关断和报警输出使能控制和激光器安全特性定购信息 PART TEMP RANGE PIN-PACKAGE ETG -40 C to 85 C 24 Thin QFN-EP* ETG+ -40 C to 85 C 24 Thin QFN-EP* + 表示无铅 (Pb)/ 符合 RoHS 标准的封装 *EP = 裸焊盘应用多速率 OC-3 至 OC-48 FEC 收发器千兆位以太网 SFF/SFP 和 GBIC 收发器 1Gbps/2Gbps/4Gbps 光纤通道 SFF/SFP 和 GBIC 收发器典型应用电路在数据资料的最后给出引脚配置 TH_TEMP MODBCOMP MODSET APCSET APCFILT2 APCFILT1 TOP VIEW MODTCOMP IN+ IN MD OUT OUT *EP 13 BIAS PC_MON BC_MON SHUTDOWN GND TX_FAULT GND *THE EXPOSED PADDLE MUST BE SOLDERED TO SUPPLY GROUND ON THE CIRCUIT BOARD. PIN1 INDICATED BY + ON LEAD-FREE PACKAGE. Maxim Integrated Products 1 本文是 Maxim 正式英文资料的译文,Maxim 不对翻译中存在的差异或由此产生的错误负责请注意译文中可能存在文字组织或翻译错误, 如需确认任何词语的准确性, 请参考 Maxim 提供的英文版资料索取免费样品和最新版的数据资料, 请访问 Maxim 的主页 :

2 ABSOLUTE MAXIMUM RATINGS Supply Voltage V to +6.0V IN+, IN-,, TX_FAULT, SHUTDOWN, BC_MON, PC_MON, APCFILT1, APCFILT2, MD, TH_TEMP, MODTCOMP, MODBCOMP, MODSET, and APCSET Voltage V to ( + 0.5V) Storage Temperature Range C to +150 C Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability. ELECTRICAL CHARACTERISTICS OUT+, OUT-, BIAS Current...-20mA to +150mA Continuous Power Dissipation (T A = +85 C) 24-Pin TQFN (derate 27.8mW/ C above +85 C) mW Operating Junction Temperature Range C to +150 C 24-Pin TQFN (derate 27.8mW/ C above +85 C) mW ( = +2.97V to +3.63V, T A = -40 C to +85 C. Typical values are at = +3.3V, I BIAS = 60mA, I MOD = 60mA, T A = +25 C, unless otherwise noted.) (Notes 1, 2) POWER SUPPLY PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS Supply Current I CC (Note 3) ma Power-Supply Noise Rejection PSNR f 1MHz, 100mA P-P (Note 4) 33 db I/O SPECIFICATIONS Differential Input Swing V ID DC-coupled, Figure V P-P Common-Mode Input V CM 1.7 LASER BIAS - V ID / 4 Bias-Current-Setting Range ma Bias Off Current = high 0.1 ma Bias-Current Monitor Ratio I BIAS / I BC_MON ma/ma LASER MODULATION Modulation Current-Setting Range Output Edge Speed I MOD (Note 5) 5 85 ma 20% to 80% (Notes 6, 7) 5mA I MOD 85mA ps Output Overshoot/Undershoot With 1pF between OUT+ and OUT- ±6 % Random Jitter (Notes 6, 7) ps RMS Deterministic Jitter (Notes 6, 8) Modulation-Current Temperature Stability Modulation-Current-Setting Error 2.7Gbps, 5mA I MOD 85mA Gbps, 5mA I MOD 85mA Mbps, 5mA I MOD 85mA Mbps, 5mA I MOD 85mA (Note 6) 5mA I MOD 10mA ±175 ±600 10mA I MOD 85mA ±125 ± load, 5mA I MOD 10mA ±20 T A = +25 C 10mA < I MOD 85mA ±15 Modulation Off Current = high 0.1 ma AUTOMATIC POWER AND EXTINCTION RATIO CONTROLS Monitor-Diode Input Current Range V ps P-P ppm/ C I MD Average current into the MD pin µa MD Pin Voltage 1.4 V MD Current Monitor Ratio I MD / I PC_MON ma/ma % 2

3 ELECTRICAL CHARACTERISTICS (continued) ( = +2.97V to +3.63V, T A = -40 C to +85 C. Typical values are at = +3.3V, I BIAS = 60mA, I MOD = 60mA, T A = +25 C, unless otherwise noted.) (Notes 1, 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS APC Loop Time Constant C APC_FILT = 0.01µF, I MD / I BIAS = 1/ µs APC Setting Stability (Note 6) ±100 ±480 ppm/ C APC Setting Accuracy T A = +25 C ±15 % I MOD Compensation-Setting Range by Bias K K = I MOD / I BIAS ma/ma I MOD Compensation-Setting Range by Temperature Threshold-Setting Range for Temperature Compensation TC TC = I MOD / T (Note 6) ma/ C T TH (Note 6) C LASER SAFETY AND CONTROL Bias and Modulation Turn-Off Delay C APC_FILT = 0.01µF, I MD / I BIAS = 1/80 (Note 6) 5 µs Bias and Modulation Turn-On Delay C APC_FILT = 0.01µF, I MD / I BIAS = 1/80 (Note 6) 600 µs Threshold Voltage at Monitor V REF Figure V INTERFACE SIGNALS Input High V HI 2.0 V Input Low V LO R PULL = 45k (typ) 0.8 V Input Current V HI = 15 V LO = V GND TX_FAULT Output Low Sinking 1mA, open collector 0.4 V Shutdown Output High Sourcing 100µA V Shutdown Output Low Sinking 100µA 0.4 V Note 1: AC characterization is performed using the circuit in Figure 2 using a PRBS or equivalent pattern. Note 2: Specifications at -40 C are guaranteed by design and characterization. Note 3: Excluding I BIAS and I MOD. Input data is AC-coupled. TX_FAULT open, SHUTDOWN open. Note 4: Power-supply noise rejection (PSNR) = 20log 10 (V noise (on VCC ) / V OUT ). V OUT is the voltage across the 15Ω load when IN+ is high. Note 5: The minimum required voltage at the OUT+ and OUT- pins is +0.75V. Note 6: Guaranteed by design and characterization. Note 7: Tested with pattern at 2.7Gbps. Note 8: DJ includes pulse-width distortion (PWD). µa 3

4 典型工作特性 ( = +3.3V, C APC = 0.01µF, I BIAS = 20mA, I MOD = 30mA, T A = +25 C, unless otherwise noted.) OPTICAL EYE DIAGRAM (2.7Gbps, PRBS, 2.3GHz FILTER) toc nm FP LASER r e = 8.2dB OPTICAL EYE DIAGRAM (1.25Gbps, PRBS, 940MHz FILTER) toc nm FP LASER r e = 8.2dB ELECTRICAL EYE DIAGRAM (I MOD = 30mA, 2.7Gbps, PRBS) toc03 1pF BETWEEN OUT+ AND OUT- 75mV/div 54ps/div 116ps/div 52ps/div ELECTRICAL EYE DIAGRAM (I MOD = 30mA, 3.125Gbps, PRBS) toc04 ELECTRICAL EYE DIAGRAM (I MOD = 30mA, 4.25Gbps, PRBS) toc05 SUPPLY CURRENT (I CC ) vs. TEMPERATURE (EXCLUDES BIAS AND MODULATION CURRENTS) toc06 SUPPLY CURRENT (ma) V 3.63V 2.97V 35 46ps/div 34ps/div TEMPERATURE ( C) IBIAS/IBC_MON (ma/ma) BIAS-CURRENT MONITOR RATIO vs. TEMPERATURE TEMPERATURE ( C) toc07 IMD/IPC_MON (ma/ma) PHOTOCURRENT MONITOR RATIO vs. TEMPERATURE TEMPERATURE ( C) toc08 IMOD (ma) MODULATION CURRENT vs. R MODSET R MODSET (kω) toc09 4

5 典型工作特性 ( 续 ) ( = +3.3V, C APC = 0.01µF, I BIAS = 20mA, I MOD = 30mA, T A = +25 C, unless otherwise noted.) IMD (ma) PHOTODIODE CURRENT vs. R APCSET R APCSET (kω) toc10 DJ (psp-p) DETERMINISTIC JITTER vs. MODULATION CURRENT 2.7Gbps I MOD (ma) toc RANDOM JITTER vs. MODULATION CURRENT toc12 10 COMPENSATION (K) vs. R MODBCOMP toc13 RJ (psrms) K (ma/ma) I MOD (ma) R MODBCOMP (kω) TEMPERATURE COMPENSATION vs. R TH_TEMP (R MODTCOMP = 500Ω) R TH_TEMP = 12kΩ toc TEMPERATURE COMPENSATION vs. R TH_TEMP (R MODTCOMP = 10kΩ) R TH_TEMP = 12kΩ toc15 IMOD (ma) R TH_TEMP = 7kΩ R TH_TEMP = 4kΩ R TH_TEMP = 2kΩ IMOD (ma) R TH_TEMP = 7kΩ R TH_TEMP = 4kΩ R TH_TEMP = 2kΩ TEMPERATURE ( C) TEMPERATURE ( C) 5

6 典型工作特性 ( 续 ) ( = +3.3V, C APC = 0.01µF, I BIAS = 20mA, I MOD = 30mA, T A = +25 C, unless otherwise noted.) FAULT 0V HOT PLUG WITH 3.3V t_init = 59.6ms toc16 FAULT 3.3V HIGH TRANSMITTER ENABLE t_on = 23.8µs toc17 LASER OUTPUT LASER OUTPUT 20ms/div 10µs/div TRANSMITTER DISABLE toc18 RESPONSE TO FAULT toc19 FAULT LASER OUTPUT 3.3V HIGH 91.2ns V PC_MON FAULT LASER OUTPUT EXTERNALLY FORCED FAULT t_fault = 160ns 20ns/div 400ns/div FAULT RECOVERY TIME toc20 V PC_MON EXTERNALLY FORCED FAULT FAULT HIGH t_init = 58ms HIGH LASER OUTPUT 40ms/div 6

7 引脚说明引脚名称功能 1 MODTCOMP 2, 5, 14, 17 调制电流温度补偿该引脚的外部电阻设置在超出温度门限时的调制电流温度系数无需温度补偿时, 该引脚浮空 +3.3V 电源 3 IN+ 4 IN- 6 7 PC_MON 8 BC_MON 9 SHUTDOWN 10, 12 GND 11 TX_FAULT 13 BIAS 15 OUT- 16 OUT+ 18 MD 19 APCFILT1 20 APCFILT2 21 APCSET 22 MODSET 23 MODBCOMP 24 TH_TEMP 同相数据输入反相数据输入发送器禁止,TTL 电平在为高电平或浮空时, 激光器输出被禁止该引脚为低电平时, 允许激光器输出光电流监视器输出该引脚输出电流通过一个外部电阻产生正比于监测二极管电流的以地为参考的输出电压偏置电流监视器输出该引脚输出电流通过一个外部电阻产生正比于偏置电流的以地为参考的输出电压关断驱动输出电压输出控制外部晶体管, 以选择关断某些电路地集电极开路输出的发送故障指示 ( 表 1) 激光器偏置电流输出调制电流反相输出输入数据为低电平时,I MOD 流入此引脚调制电流同相输出输入数据为高电平时,I MOD 流入此引脚监测光电二极管输入该引脚接监测光电二极管的阳极要求对地外接一只电容, 以滤除高速交流监测光电流在引脚 19 (APCFILT1) 和引脚 20 (APCFILT2) 之间连接一只电容 (C APC ), 用于设置 APC 反馈回路的主极点 ( 参见引脚 19 ) 在此引脚和地之间连接一个电阻, 用于设置所需的平均光功率在此引脚和地之间连接一个电阻, 用于设置所需的恒定调制电流部分基于偏置的调制电流补偿将偏置电流耦合至调制电流 I BIAS 的镜像电流流过一个外部电阻无需耦合时, 该引脚浮空温度补偿门限该引脚的外接电阻设置温度门限, 超出该温度时将对调制电流进行补偿 EP 裸焊盘将裸焊盘焊接到电路板地, 以达到指定的散热和电气特性 7

8 SINGLE ENDED DIFFERENTIAL 100mV (min) 1200mV (max) 200mV (min) 2400mV (max) VOLTAGE V IN+ V IN- (V IN+ ) - (V IN- ) OUT- 30Ω 30Ω Z 0 = 30Ω 0.5pF I OUT+ 30Ω OSCILLOSCOPE CURRENT OUT+ Z 0 = 30Ω Z 0 = 50Ω I OUT+ I MOD 75Ω 50Ω TIME 图 1. 所需的输入信号和输出极性图 2. 特征参数的测试电路 SOURCE NOISE HOST BOARD FILTER DEFINED BY SFP MSA L1 1µH OPTIONAL MODULE TO LASER DRIVER VOLTAGE SUPPLY C1 0.1µF C2 10µF C3 0.1µF OPTIONAL 图 3. 电源滤波器详细说明激光驱动器主要包括三个部分 : 高速调制驱动器带 ERC 的偏置电流单元及保护电路该电路设计优化用于高速低压 (+3.3V) 工作方式 ( 图 4) 高速调制驱动器输出级由高速差分对儿和可编程调制电流源组成针对驱动 15Ω 负载进行优化 ; 要求调制电流达到 60mA 时, OUT- 的最低瞬态电压为 0.7V; 要求调制电流为 60mA 至 85mA 时,OUT- 的最低瞬态电压为 0.75V 超过 60mA 运行时可采用交流耦合, 保证激光器上具有足够的电压, 以达到驱动器输出电压的要求为了与激光二极管连接, 需采用一只阻尼电阻 (R D ) 进行阻抗匹配串联阻尼电阻与激光二极管的等效串联电阻 (ESR) 总和应等于 15Ω 为减小由激光二极管寄生电感引起的过冲, 可能需要一个 RC 并联网络详细信息, 请参考应用笔记 274:HFAN-02.0:Interfacing Maxim Laser Drivers with Laser Diodes 数据速率较高时, 任何加载在激光二极管阴极的电容都会恶化光输出性能由于 BIAS 输出直接与激光二极管阴极连接, 可利用电感将 BIAS 引脚的寄生效应与激光器阴极隔离开, 使该引脚的寄生电容最小消光比控制消光比 (r e ) 为激光器导通状态的功率除以关断状态的功率若峰值功率和平均功率保持不变, 则消光比保持恒定 : r e = (2P AVG + P P-P ) / (2P AVG - P P-P ) 8

9 SHUTDOWN INPUT BUFFER DATA PATH IN+ IN- OUT- OUT+ R D SHUTDOWN TX_FAULT SAFETY LOGIC AND POWER DETECTOR I MOD ENABLE I BIAS ENABLE I MOD BIAS I BIAS R PULL = 45kΩ I MD 1 I BIAS V REF APCSET R APCSET PC_MON x1/2 R PC_MON xtc x268 xk BC_MON I BIAS 82 T > T TH I APCSET MD I MD C MD R BC_MON T x1 V REF TH_TEMP MODTCOMP MODSET MODBCOMP APCFILT1 APCFILT2 R TH_TEMP R MODTCOMP R MODSET R MODBCOMP C APC 图 4. 功能框图通过 APC 调节平均功率, 保持激光器耦合到光电二极管的电流恒定激光器斜率效率 (η) 降低时, 通过补偿调制电流能够在整个有效使用期限内和温度范围内保持峰值功率恒定 : P AVG = I MD / ρ MON P P-P = η x I MOD 基于偏置的调制补偿按照用户选择的比例系数 (K) 调节调制电流, 以便在偏置电流随温度升高而增大时, 保持峰值光功率不变详细资料请参考应用笔记 1119:HFAN : Maintaining the Extinction Ratio of Optical Transmitters Using K-Factor Control K = I MOD / I BIAS 这提供了增大电流所需要的一次逼近, 以保持峰值功率恒定斜率效率随着温度的增加将明显降低当温度超出用户定义的门限 (T TH ) 时, 还可提供额外的温度补偿 9

10 POR AND COUNTER 60ms DELAY I MOD ENABLE COUNTER 60ms DELAY 100ns DELAY I BIAS ENABLE R PC_MON PC_MON R BC_MON BC_MON I MD 1 I BIAS 82 V REF V REF EXCESSIVE APC CURRENT SETPOINT COMP COMP R S RS LATCH Q CMOS SHUTDOWN TX_FAULT EXCESSIVE MOD CURRENT SETPOINT TTL OPEN COLLECTOR 图 5. 简化的安全电路表 1. 典型故障条件 1 If any of the I/O pins are shorted to GND or (single-point failure; see Table 2), and the bias current or the photocurrent exceeds the programmed threshold. 2 End-of-life (EOL) condition of the laser diode. The bias current and/or the photocurrent exceed the programmed threshold. 3 Laser cathode is grounded and photocurrent exceeds the programming threshold. 4 No feedback for the APC loop (broken interconnection, defective monitor photodiode), and the bias current exceeds the programmed threshold. 10

11 表 2. 不同单点故障的电路响应 PIN CIRCUIT RESPONSE TO OVERVOLTATGE OR SHORT TO CIRCUIT RESPONSE TO UNDERVOLTAGE OR SHORT TO GROUND TX_FAULT Does not affect laser power. Does not affect laser power. Modulation and bias currents are disabled. Normal condition for circuit operation. IN+ IN- MD The optical average power increases, and a fault occurs if V PC_MON exceeds the threshold. The APC loop responds by decreasing the bias current. The optical average power decreases and the APC loop responds by increasing the bias current. A fault state occurs if V BC_MON exceeds the threshold voltage. This disables bias current. A fault state occurs. The optical average power decreases, and the APC loop responds by increasing the bias current. A fault state occurs if V BC_MON exceeds the threshold voltage. The optical average power increases and a fault occurs if V PC_MON exceeds the threshold. The APC loop responds by decreasing the bias current. The APC circuit responds by increasing the bias current until a fault is detected; then a fault* state occurs. SHUTDOWN BIAS Does not affect laser power. If the shutdown circuitry is used, the laser current is disabled. In this condition, the laser forward voltage is 0V and no light is emitted. Does not affect laser power. Fault state* occurs. If the shutdown circuitry is used, the laser current is disabled. OUT+ The APC circuit responds by increasing the bias current until a fault is detected; then a fault state* occurs. Fault state* occurs. If the shutdown circuitry is used, the laser current is disabled. OUT- Does not affect laser power. Does not affect laser power. PC_MON Fault state* occurs. Does not affect laser power. BC_MON Fault state* occurs. Does not affect laser power. APCFILT1 APCFILT2 I BIAS increases until V BC_MON exceeds the threshold voltage. I BIAS increases until V BC_MON exceeds the threshold voltage. MODSET Does not affect laser power. Fault state* occurs. APCSET Does not affect laser power. Fault state* occurs. * 故障状态触发 TX_FAULT 引脚, 禁止调制和偏置电流, 并触发 SHUTDOWN 引脚 I BIAS increases until V BC_MON exceeds the threshold voltage. I BIAS increases until V BC_MON exceeds the threshold voltage. 安全电路安全电路包括禁止输入 () 锁存故障输出 (TX_FAULT) 和故障检测器 ( 图 5) 该电路监视激光驱动器的工作状况, 一旦检测到故障状态, 就强行关断驱动器 ( 见表 1) 根据 SFP MSA 的要求,TX_FAULT 引脚应接一个 4.7kΩ 至 10kΩ 电阻上拉到单点故障可以是与或 GND 的短路有关电路对不同单点故障的响应情况参见表 2 发送故障状态会一直被锁定, 直到或引脚被触发复位利用可选的关断电路, 激光驱动器提供备用的激光二极管关断功能, 参见典型应用电路关断晶体管避免了由于激光器的单点故障而发生的不安全情况安全电路电流监测器能够监视 (BC_MON PC_MON) 偏置电流 (I BIAS ) 和光电流 (I MD ) 通过映射部分电流, 并在外部接地电阻产生电压实现监视功能当 PC_MON 或 BC_MON 的电压大于 V REF 时, 进入故障状态例如, 在每个监测器输出端接 100Ω 的电阻到地, 可以得到以下电压 : V BC_MON = (I BIAS / 82) x 100Ω V PC_MON = I MD x 100Ω 需要高精度测量偏置电流和光电二极管电流时, 可以使用外部检测电阻片内隔离电阻减少了实现该功能所需要的元件数量 11

12 表 3. 光功率关系式 PARAMETER SYMBOL RELATION Average Power P AVG P AVG = (P 0 + P 1 ) / 2 Extinction Ratio r e r e = P 1 / P 0 Optical Power of a One P 1 P 1 = 2P AVG x r e / (r e + 1) Optical Power of a Zero P 0 P 0 = 2P AVG / (r e + 1) Optical Amplitude P P-P P P-P = P 1 - P 0 Laser Slope Efficiency η η = P P-P / I MOD Modulation Current I MOD I MOD = P P-P / η Threshold Current I TH P 0 at I I TH Bias Current (AC-Coupled) Laser to Monitor Transfer I BIAS I BIAS I TH + I MOD / 2 ρ MON 注 : 假设 50% 的平均输入占空比和符号密度 I MD / P AVG 设计步骤设计激光发射器时, 通常用平均功率和消光比表示光输出表 3 列出的关系式有助于平均光功率和调制电流之间的换算在光信号的符号密度和占空比为 50% 时, 这些关系式有效给定平均激光功率 (P AVG ) 和消光比 (r e ), 可根据表 3 计算偏置电流和调制电流为了适当设置这些电流, 需要了解激光器特性, 以监视传输效率 (ρ MON ) 和斜率效率 (η) 设置监测二极管电流在任何时候都工作在 APC 模式偏置电流将自动设置, 使平均光功率由 APCSET 的外部电阻确定 : P AVG = I MD / ρ MON APCSET 引脚控制监测二极管电流的设置点内部电流调节器以与 MODSET 相同的方式建立 APCSET 电流参考典型工作特性中 Photodiode Current vs. R APCSET 的关系曲线, 选择 +25 C 下所需电流对应的 R APCSET 值激光驱动器自动调整偏置, 以保持恒定的平均功率对于直流耦合的激光二极管 : I AVG = I BIAS + I MOD / 2 设置带补偿的调制电流由激光器的斜率效率决定调制电流 : I MOD = 2 x P AVG / η x (r e - 1) / (r e + 1) 的调制电流包括 : 静态调制电流 (I MODS ) 与 I BIAS 成正比的电流和与温度成正比的电流由 MODSET 设置的 I MOD 电流通过内部电流调节器建立, 保持外部编程电阻上电压为 V REF 参考典型工作特性中 Modulation Current vs. R MODSET 的关系曲线, 选择 +25 C 下所需电流对应的 R MODSET 值 : I MOD = I MODS + K x I BIAS + I MODT I MODS = 268 x V REF / R MODSET I MODT = TC x (T - T TH ) T > T TH I MODT = 0 T < T TH MODBCOMP 引脚的外部电阻用来设置与 I BIAS 成比例的电流 MODBCOMP 引脚开路将断开 I BIAS 与 I MOD 之间的耦合关系 : K = 1700 / ( R MODBCOMP ) ±10% 若 I MOD 必须从 I MOD1 增加到 I MOD2, 以便使消光比在高温下保持不变, 所需补偿因数为 : K = (I MOD2 - I MOD1 ) / (I BIAS2 - I BIAS1 ) 附加温度补偿的门限通过 TH_TEMP 引脚的电阻设置 : T TH = -70 C MΩ / (9.2kΩ + R TH_TEMP ) C ±10% 超过 T TH 时, 温度补偿系数由 R MODTCOMP 设置 MODTCOMP 引脚开路将禁止附加的温度补偿 : TC = 1 / (0.5 + R MODTCOMP (kω)) ma/ C ±10% I MD = 1/2 x V REF / R APCSET 12

13 电流条件 (I MOD 60mA), 直流耦合 OUT+ 和 OUT- 上的最小电压为 0.7V 对于 : V DIODE = 二极管偏置电压 (1.2V 典型值 ) R L = 二极管偏置电阻 (5Ω 典型值 ) R D = 串联匹配电阻 (20Ω 典型值 ) 为了满足电流条件 : V OUT+ = - V DIODE - I MOD x (R D + R L ) - I BIAS x R L 0.7V 电流条件 (I MOD > 60mA), 交流耦合对于要求调制电流大于 60mA 的应用来说, 如果激光器采用直流耦合, 留出的空间将不足以保证激光驱动器的正常运行为避免该问题的发生, 的调制输出可通过交流耦合至激光二极管的阴极这就需要一只外部上拉电感, 将调制输出直流偏置在这种配置将激光器正向电压与输出电路隔离, 并允许 OUT+ 输出在供电电压 ( ) 处上下波动采用交流耦合时, 调制电流可以设置到 85mA 有关交流耦合激光驱动器与激光二极管的详细信息, 请参考应用笔记 274:HFAN-02.0: Interfacing Maxim Laser Drivers with Laser Diodes 为满足电流条件 : V OUT+ = - I MOD / 2 x (R D + R L ) 0.75V 确定 C APC 必须合理选择 APC 环路滤波电容 C APC, 以平衡快速开启和减小低频时数据模板相互影响的要求低频截止电容为 : C APC (µf) 68 / (f 3dB (khz) x (η x ρ MON ) 1.1 ) 高频噪声可用 MD 引脚与地之间的外部电容 C MD 滤除 : C MD C APC / 4 设计, 以便开启时间小于 1ms, 以适合大多数激光器增益 (η x ρ MON ) 选择更小的 C APC 值, 将缩短开启时间对于某些激光器增益, 在低数据速率下需要仔细考虑开启时间和低频截止接口模型图 6 和图 7 给出了简化的激光驱动器的输入和输出电路若采用裸片, 则采用绑定线寄生参数代替封装寄生参数 IN+ PACKAGE 0.7nH 16kΩ PACKAGE 0.7nH OUT- 0.11pF 0.11pF 5kΩ 0.7nH OUT+ 5kΩ 0.11pF IN- 0.11pF 0.7nH 24kΩ 图 6. 简化的输入结构图 7. 简化的输出结构 13

14 布局考虑为尽可能降低损耗和串扰, 应保持输出与激光二极管之间尽可能短的连线采用良好的高频布局技巧和带有不间断地线层的多层电路板, 以最小化 EMI 和串扰应该采用低损耗绝缘电路板同时, 数据输入和模块输出应该采用阻抗受控的传输线激光器安全性和 IEC 825 单独采用激光驱动器并不保证发射器的设计符合 IEC 825 标准必须仔细考虑整个发射器电路及器件选择每个用户必须明确具体应用所要求的容错等级, 确保 Maxim 产品不会作为系统的一个部分被设计或使用到外科移植手术, 用于支撑或维持生命, 或其它任何可能因为 Maxim 产品失效所导致的人体伤害甚至死亡的应用领域裸焊盘 (EP) 封装 24 引脚 TQFN 的裸焊盘提供了一个低热阻通路, 有助于 IC 散热该焊盘同时也是的电气地, 必须被焊接至电路板地, 以获得良好的散热性能和电气性能详细信息, 请参考 Maxim 应用笔记 862:HFAN-08.1:Thermal Considerations of QFN and Other Exposed-Paddle Packages, 应用笔记可从网站获得芯片信息 TRANSISTOR COUNT: 3754 PROCESS: SiGe/BiPOLAR 14

15 典型应用电路 +3.3V OPTIONAL SHUTDOWN CIRCUITRY +3.3V CDR 0.1µF 0.1µF 100Ω TX_FAULT VCC SHUTDOWN IN+ IN- OUT- OUT+ 15Ω 10Ω +3.3V 0.01µF R MODBCOMP R MODTCOMP R TH_TEMP MODBCOMP MODTCOMP TH_TEMP BIAS MD GND MODSET APCSET APCFILT1 APCFILT2 BC_MON FERRITE BEAD C MD RMODSET PC_MON RAPCSET C APC RBC_MON RPC_MON REPRESENTS A CONTROLLED-IMPEDANCE TRANSMISSION LINE. 封装信息如需最近的封装外形信息和焊盘布局, 请查询封装类型封装编码文档编号 24 TQFN-EP T

16 修订历史修订次数修订日期说明修改页 0 1/04 最初版本将数据资料由 1Gbps 至 2.7Gbps 更改为 155Mbps 至 2.7Gbps 全部 1 7/05 在定购信息表中加入了无铅封装为 Electrical Characteristics 表中的确定性抖动参数增加了 622Mbps 和 155Mbps 测试条件在典型应用电路中增加了 100Ω 电阻将最大数据速率由 2.7Gbps 增加至 4.25Gbps 在应用中的光纤通道 SFF/SFP 和 GBIC 收发器之前增加了 4Gbps 全部 /08 将 Absolute Maximum Ratings 中连续功耗的降额因数由 20.8mW/ C 更改为 27.8mW/ C 在典型工作特性中增加了新的 TOC 4 和 TOC 5 曲线图将图 4 中的 V BG 更改为 V REF 将芯片信息部分中的晶体管数量由 1184 更改为 Maxim 北京办事处北京 8328 信箱邮政编码免费电话 : 电话 : 传真 : Maxim 不对 Maxim 产品以外的任何电路使用负责, 也不提供其专利许可 Maxim 保留在任何时间没有任何通报的前提下修改产品资料和规格的权利 16 Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA Maxim Integrated Products 是 Maxim Integrated Products, Inc. 的注册商标

MAX3737 DS.C

MAX3737 DS.C 19-2818; Rev 2; 7/04, +3.3V, 155Mbps 2.7Gbps,, (ERC) (APC) APC, 5mA 60mA ( 85mA) 100mA, FP/DFB () (TX_FAULT),, APC SFF-8472 SFP MSA 32 5mm x 5mm QFN QFN, -40 C +85 C OC-3 OC-48 FEC SFF/SFP GBIC 1Gbps/2Gbps