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1、MAX3963155Mbps Preamplifier for FDDI and ATM LAN Fiber Optic ReceiversGeneral Description:The MAX3963 is a low-noise transimpedence preamplifier for FDDI and 155Mbps ATM optical receivers. The MAX3963s dynamic range is optimized for use in multimode LED-based applications.The preamplifier converts a
2、 small photodiode current to a differential voltage, with typical transimpedance of 2K.Input-referred noise of only 21nA allows detection of signal as small as 267nA, while pulse-width distortion is only 85ps with a 60uA input signal. In a 1300nm multimode receiver, with responsivity of 0.7A/W, the
3、MAX3963s dynamic range spread from -36dB to -13.7dBm.The circuit operates from a single +5V supply, and typically consumed only 60mW power.The MAX3963 die includes a filter connection, which provides positive bias for the photodiode through a 1K resistor to VCC. The feature, combined with the small
4、die size, allows the MAX3963 to fit easily into a TO-style package with a photodiode.The differential outputs are back terminated with 60 per side, allowing the easy use of filters to improve sensitivity.The MAX3963 is designed to be used with the MAX3964 limiting amplifier IC. It is available in an
5、 8-pin SO package and as dice.Applications: FDDI、155Mbps ATMFeatures:21nA Total RMS Noise、22K Differential Transimpedance、180MHz Bandwidth、60mW Typical Power Consumption、60uA Peak Input Current、Low,85ps Pulse-Width DistortionOrdering Information:PARTTEMP.RANGEPIN-PACKAGEMAX3963CS/A0 to +708 SOMAX396
6、3C/D0 to +70DicePin ConfigurationTypical Application Circuit:Absolute Maximum Ratings:VCC .-0.5V to +7.0VContinuous Current:IN.5mA OUT+, OUT- .25mABYP .5mAContinuous Power Dissipation (TA = +70C)SO (derate 5.88mW/C above +70C) .471mWStorage Temperature Range .-65C to +150CLead Temperature (soldering
7、, 10sec) .+300C Operating Junction Temperature (die) .-55C to +150C Processing Temperature (die) .+400CDC Electrical Characteristic:(VCC = +4.5V to +5.5V, CBYP = 100pF, 1kW load between OUT+ and OUT-, TA = 0C to +70C. Typical values are at VCC = 5.0V, TA = +25C, unless otherwise noted.) (Note 1)AC E
8、lectrical Characteristic:(VCC = +4.5V to +5.5V, CBYP = 100pF, CIN = 1.15pF, TA = +25C, unlessotherwise noted.) (Notes 2, 3)Note 1: Dice are tested at TA = +25C only.Note 2: AC characteristics are guaranteed by design.Note 3: COUT is the differential output capacitive load.Note 4: PWD = (width of wid
9、er pulse) - (width of narrower pulse) / 2. Input is a 155Mbps 1-0 pattern, with rise time approximately 2ns.Note 5: Measured with a 117MHz, 3-pole Bessel filter.Note 6: Measured with COUT = 5pF, TA = +25C.Pin Description:PINNAMEFUNCTION1, 3N.C.No Connect. No internal connection to the die. 2INSignal
10、 Input4BYPConnection for optional noise-reducing capacitor5GNDSignal Ground6OUT+Noninverting Voltage Output. Current flowing into IN causes VOUT+ to increase.7OUT-Inverting Voltage Output. Current flowing into IN causes VOUT- to decrease.8VCCSupply VoltageFILTER*Connection for 1k filter resistor. Th
11、is pad is accessible on the die only.Detailed Description:The MAX3963 transimpedance amplifier is designed for 155Mbps fiber optic applications. Figure 1 is a function- al diagram of the MAX3963, which comprises a transimpedance amplifier and a paraphrase amplifier with emitter-follower outputs. Tra
12、nsimpedance Amplifier:The signal current at the input flows into the summing node of a high-gain amplifier. Shunt feedback through RF converts this current to a voltage with a 10k gain.Paraphrase Amplifier :The paraphrase amplifier converts single-ended signals to differential signals and introduces
13、 a 2x voltage gain. This signal drives a pair of internally biased emitter followers, Q1 and Q2, which form the output stage. Resistors R1 and R2 provide back termination at the output, providing a 120 differential output impedance. The output emitter followers are designed to drive a 1kW differenti
14、al load between OUT+ and OUT-. Higher out- put impedances can also be driven, resulting in slightly increased gain and output voltage swing. The MAX3963 will not drive a 50 grounded load. The MAX3963 outputs may be AC coupled to a limiting amplifier.Applications Information Optical-Power Relations:M
15、any of the MAX3963 specifications relate to the input signal amplitude. When working with fiber optic receivers, the input is usually expressed in terms of average optical power and extinction ratio. The relations shown in Table 1 are helpful for converting optical power to input signal when designi
16、ng with the MAX3963. These relations are true if the average data duty cycle is 50%.Calculating Sensitivity and Overload:The MAX3963s input-referred RMS noise current (in) generally dominates receiver sensitivity. In a system where the bit error rate is 1E-10, the signal-to-noise ratio must always e
17、xceed 12.7. The sensitivity, expressed in average power, can be estimated as shown in the following equation:Where is the photodiode responsivity in A/W .Input Overload:The overload is the largest input that the MAX3963 accepts while meeting specifications. A larger input causes increased pulse-widt
18、h distortion. Output Filter:The MAX3963s noise can be reduced by filtering the output signal. For digital communications systems, a linear-phase filter with -3dB low pass response of (0.7 x data rate) is recommended. A single-pole filter implemented with a capacitor across the outputs also reduces n
19、oise, and consumes less board space than a linear-phase filter. The following equation represents the filter frequency:Where ROUT is the MAX3963 differential output resistance (typically 120), and COUT is the differential out- put load capacitance. For 155Mbps receivers, an 11pF capacitor is recomme
20、nded.Layout Considerations:Use good high-frequency design and layout techniques. The use of a multilayer circuit board with separate ground and VCC planes is recommended. Bypass VCC and connect the GND pin to the ground plane with traces kept as short as possible. Ensure that common- mode output cap
21、acitance is less than 2pF per output.Low-Capacitance Input Design Considerations:Noise performance and bandwidth are adversely affected by stray capacitance on the input node. Every effort must be made to minimize capacitance on this pin. Select a low-capacitance photodiode, and use good high freque
22、ncy design and layout techniques. The MAX3963 is optimized for 1.0pF of capacitance on the input, approximately the capacitance of a photo detector diode packaged in a header. When using the SO package version of the MAX3963, the package capacitance is about 0.3pF. This means that great care must be
23、 used to reduce input capacitance. The PC board between the MAX3963 input and the photodiode can add parasitic capacitance. Keep the input line short, and remove power and ground planes beneath it. Assembling the MAX3963 in die form provides the best possible performance. Parasitic capacitance can b
24、e reduced to a minimum, resulting in the lowest noise and the best bandwidth.Wire Bonding:For high current density and reliable operation, the MAX3963 uses goldmetallization.Chip Topography:MAX3963-应用于光纤分布式数据接口或者局域网内光纤异步传输模式接收机的155Mbps前置放大器概述：MAX6613是一款应用于光纤分布式数据接口，155Mbp局域网内光纤异步传输模式接收机的低噪声跨阻抗前置放大器。
25、在以多模LED为基础的应用中它的动态范围能够最佳化。这款放大器典型的跨阻抗的为22K，使其可以将微弱的光电二极管的电流转换为差分电压。当输入信号为60uA时脉冲宽度失真仅为85ps，输入端的有关噪声仅有21nA，这时放大器可以检测如267nA的微弱信号。在响应特性为0.7A/W的1300nm的多模接收机中，MAX3963的动态范围从-36dBm-13.7dBm。这个电路采用+5V单电源供电，典型功率消耗为60mW。MAX3963封装包括一个filter管脚，它通过一个阻值为1K的电阻与VCC相连，为光电二极管提供正向偏压。上述特征和小的封装尺寸使MAX3963更易于与光电二极管以TO-styl
26、e方式封装。两个输出端分别连接60的电阻，允许使用滤波器提高灵敏度。MAX3963经常与MAX3964的限幅集成放大电路中一起使用。它在8脚的同样的封装与设备中都可以使用。应用：光纤分布式数据接口、155Mbps的异步传输模式接收机特征：总体均方根噪声：21nA差分跨阻抗：22k频带宽度：180MHz典型的功率损耗：60mW最大输入电流：60uA脉宽为85ps的失真控制信息：芯片温度范围封装管脚MAX3963CSA0708脚SOMAX3963C/D070dice管脚图： 典型应用电路：极限参数：VCC-0.5V+7.0V连续电流：IN-5mA OUT+、OUT- -25mA BYP- 5mA连
27、续功率损耗（TA=+70）：SO-471mV存储温度范围-65150导线温度（焊接，10sec）-+300操作连接点温度 - -55150处理温度 - +400不在以上所述极限参数条件下使用会对设备造成永久性的损害。长时间最大限度的使用设备会影响它的可靠性。直流电气特性：（VCC=+4.5V+5.5V,CBYP=100pF,OUT+与OUT-之间有1K的电阻，TA=0+70，典型值为VCC=5V，TA=+25，除非另外注明）参数符号条件最小 典型 最大单位输入偏压VIN输入电流=0uA60uA 1.6 1.8V供给电流ICC输入电流=0uA 12 20mA小信号Z21差分输出，Iin60uA1
28、7.5 22 26.3K一般模式VoutVCC-2.85V供给功率PSRRf1MHz,参考输出35dB输出电阻ROUT45 60 68最大差分VoutVODIIN=80uA 2.2V交流电气特性：（VCC=+4.5V+5.5V,CBYP=100pF,CIN=1.15pF,TA=+25,除非另外注明）参数符号条件最小 典型 最大单位小信号频带宽度BW-3dBCOUT=5pF100 180 220MHz脉冲宽度失真PWDIIN=60uAp-p（注解4） 85 160ps参考输入的均方根噪声IN注解5 21 24.5nA注解6 37注解1：只能在TA=+25测试设备注解2：交流电气特性由设计决定注解
29、3：CIN是输入端的合计电容，COUT为差分输出电容性负载注解4：PWD=（宽脉冲脉宽-窄脉冲脉宽）/2,输入为1-0模式155Mbps，上升时间大约为2ns注解5：用117MHz的3电极贝塞尔滤波器测量注解6：在TA=+25用COUT=5pF测量管脚介绍：管脚名称作用1,3N.C空接2IN信号输入4BYP接选择性噪声减少的电容5GND接地端6OUT+正向电压输出端，IN端输入电流使VOUT+增大7OUT-反向电压输出端，IN端输入电流使VOUT-减小8VCC电压供给-滤波器连接1K的电阻MAX3963 C/D详细说明：跨阻抗放大器MAX3963因155Mbps光纤应用而生。图一为它的功能表，
30、由一个跨阻抗放大器和一个接有发射输出端的倒相放大器组成。跨阻抗放大器：输入端电流信号流入高增益放大器的求和节点。RF作为分流反馈电阻，以10K的阻值将输入电流转变为电压值。倒相放大器：倒相放大器将单端输入的信号转变为差分信号，同时引进了两倍的电压增益。这个信号由内部的一对偏压射极跟随器Q1和Q2产生，Q1和Q2组成输出级。阻值为120的差分输出阻抗R1与R2给输出端提供终止反馈。输出端的射极跟随器是为了驱动OUT+和OUT-之间的阻值为1K的差分负载。高输出阻抗同样可以被驱动，同时会伴随增益的轻微增大，输出电压的起伏。MAX3963不能驱动接地的阻值为50的负载，它的输出端通常与限幅放大器连接
31、。应用信息-光电关系：许多MAX3963的规格同输入信号的幅度有关，应用于光纤接收机时，输入通常以平均输出功率与消光比的形式表示。表一所呈现的关系对于应用MAX3963时将输出功率转化成输入信号非常有用。当且仅当平均数据的占空比为40%时表一呈现的关系成立。灵敏度计算与超载-灵敏度计算与MAX3963输入有关的均方根噪声电流（IN）通常控制着接收机的灵敏度。在比特误码率为1E-10的系统中，信噪比肯定超过12.7。用平均功率表示的灵敏度，可以用下面的等式来估算：,这里为光电二极管的响应度，单位为A/W。输入端超载：超载即在符合规格条件下MAX963所能承受的最大输入。更大的输入信号会加大失真的
32、脉宽。表一：光电关系（假设平均数据的占空比为50%）参数符号关系平均功率PAVEPAVE=（P0+P1）/2消光比rere=P1/P0输出功率1P1P1=2 PAVE（re）/( re+1)输出功率0P0P1=2 PAVE/( re+1)信号幅度PINPUTPINPUT=P1-P0=2PAVE（re-1）/( re+1)图二：输出功率的定义输出滤波器：通过输出滤波器MAX3963的噪声会减小，数字通信系统建议使用（数据传输速率为0.7bit/s）-3dB的线性相位低通滤波器。在两个输出端间加电容实现单级滤波同样可以减小噪声，同时比线性相位滤波器节省板空间。下面的等式表示滤波器的频率：这里ROU
33、T是MAX3963的差分输出阻抗（典型值为220），COUT是差分输出端的负载电容。在155Mbps的接收机中，建议使用11pF的电容。布局思路：使用高频率的布局设备，建议使用独立的接地与VCC层。绕开VCC尽量少用导线将GND端练到接地层。确保普通模式下每个输出端的电容值小于2pF。低输入电容设计思路：输入节点的寄生电容不同的影响噪声性能与带宽，必须想办法减小这个电容。选择一个低电容值的光电二极管，并使用高频率的布局设备。输入端接有1.0pF的电容能使MAX3963的性能最佳化，近似等于封装的光电探测器的二极管的容值。当MAX3963以SO形式封装时，其封装电容值接近0.3pF。这意味着要尽量减小输入电容值。MAX3963输入端与光电二极管间的印刷电路板可加寄生电容。尽量使输入线短些，将电源层与接地层移到输入线下端。以die模式封装的MAX3963可能达到最好的性能，此时寄生电容值能减到最小，而且噪声最小，带宽最好。导线压焊:对于电流密度大而且可靠的操作，MAX3963采用金属封装。芯片：
