IC基本电气特性-华为内部员工培训资料.docx

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1、IC 根本电气特性-华为内部员工培训资料IC 根本电气特性Quiescent current 静态电流Standby current 低功耗电流Dropout voltage (LDO 特性)压降的输入电压Efficiency 功率Transient response 顺势特性Line regulation 线路调整器Load regulation 负载调整率Power supply rejection 电源排解/抑制NoiseAccuracy 准确性IC 量测ICLDO构造框图Capacitor电容 reference参考 电压 error amplifier 误差信号放大器Pass ele

2、ment 无源元件二极管dynamic load 动态负载主要模块包括;Voltage Reference 参考电压Error Amplifier 误差信号放大器Feedback Network 反响网络 Series-pass Element无源元件二极管优点：简洁、输出纹波电压低 、精彩的 line 和负载稳压、对负载和 line 的变化响应快速 、电磁干扰 (EMI) 低缺点：效率低 、假设需要冷却设备，则要求较大的空间IC 根本电气特性Quiescent Current & Standby CurrentQuiescent Current(Ground current):Thediff

3、erencebetweeninputandoutput。Low quiescent current is necessary to maximize the efficiency. 低静态电流是最大限度地提高效率必要条件 。:Standby CurrentThe input current drawn by a regulator when the output voltage is disabled by a shutdown signal.Quiescent Current and Output CurrentThevaluecurrentofisquiescentmostlydeterm

4、inedbytheseriespasselement,topologies,ambient temperature, etc. 静态电流的值主要是一系列无源元件，拓扑构造，环境温度等 确定的具体特性与IC 构造、制程亲热相关u Low-DropoutLinear Regulators低压差线性稳压器u 传统的三端稳压器如：LM78xxIC 根本电气特性 Dropout Voltage特有规格Vdrop 的典型值是 2V，看到很多 7805 应用 时都会背着一个散热器。LM3172V LM11171.2V。调整管承受 的 结 构LM317 输出Darlington g Vdrop= Vsat+2

5、V beVdrop=Vsat+Vbe0.9VVdrop=Vsat0.150.4V OSVdrop=Io X Ron35350mv OSVdrop=Vsat+Vgs1V不同调整管构造的比较：1. The NMOS pass element is most advantageous due to its low on resistance. Unfortunately, the gate drive difficulties make it less than ideal in applicaitons and as a result there are few NMOS LDOs availab

6、le.传统上，PNP 双极型晶体管应用到低压线性稳压器，主要是由于它很简洁实现了低压降电压。2. Traditionally, the PNP bipolar transistor hasbeen applied to low dropout applications, primarily because it easily enables a low drop out voltage. However, it has a high quiescentcurrentandlowefficiency,whicharenotidealinapplicationswheremaximizing ef

7、ficiency is a priority. 然而，它的高静态电流和低效率，这是不抱负的应用最大限度地提高了效率是一个优先事项。3. PMOS devices have been highly developed and now have performance levelsexceedingmost bipolar devices.PMOS 上设备已经高度兴旺，现在的性能水平超过最双极器件。Dropout voltage：the input-to-output differential voltage at which the circuitceases to regulate again

8、st further reductions in input voltage; this point occurs when the input voltage approaches the output voltage. 压降：对输入至输出差分电压在电路不再标准对进一步削减输入电压;这一点时发生的输入电压接近输出电压。Vds=Vo-VinIC 根本电气特性Efficiencyu The efficiency of a LDO regulator is limited by the quiescent current andinput/output voltage as follows:效率是

9、有限的 LDO 稳压器的静态电流和输入/输出电压如下：输入电压。降低;这一点时发生的输入电压接近输出电压Efficiency = (I V )100V= V + VooI + IVoqii _ mino dropu To have a high efficiency LDO regulator, drop out voltage and quiescent current must be minimized.具有高效率的 LDO 稳压器，电压和辍学静态电流必需削减到最低限度IC 根本电气特性Load Regulationu Load Regulation:A measure of the ci

10、rcuits ability to maintain the specified output voVo / DIo(Dvarying load co)nditions. 衡量电路的力量，保持指定的输出电压在不同负载条件下。The load regulation is limited by the open loop current gain of the system. As noted from the above equation, increasing dc open-loop current gain improves load regulation. 负荷调整是有限的开环电流增益的

11、系统。正如上述方程，增加直流开环电流增益改善负载调整。u Line Regulation:a measure of the circuits ability to maintain the specified output voltage with varying(DVo /DVi)其中， Rds 为调整管 Q1 源漏等效电阻。input voltage.衡量这条赛道的力量，保持指定的输出电 voltage.open 环电流增益改善负载调整。u Increasing dc open loop current gain improves the line regulation.电流增益提高了线路

12、调整提高直流开环Line Transient ResponseOutputVoltageWithRespecttoInputVolta geIC 根本电气特性Transient Responseu Transient Response:the maximum allowable output voltage variation for a load current (input voltage) step change. 瞬态响应：允许的最大输出电压变化的负载电流输入电压一步变化。u The transient response is a function of the output capa

13、citor value (Co), the ESR of the output capacitor, the buypass capacitor (Cb), and the maximum load-current (Io,max). 瞬态响应是一个功能的输出电容值公司中，电子自旋共振的输出电容器，电容器的buypass炭黑 ，最大负载电流 Io ，最大值 。Where t1 corresponds to the closed loopbandwidth. ESR is the voltage variation resulting from the presence of the ESR o

14、f the output capacitor. ESR is proportionalto ESR.凡t1 闭环带宽。esr 是电压变化造成在场的状况下的 ESR 的输出电容器。esr 成正比 esr。TransientResponseofLDO Regulator瞬态响应 LDO 稳压器输出电容的影响ESL load-transient response 负载瞬态响应ESR load-transientresponseESL 影响比较小，但不适宜的 PCB 布线同样使得性能下降。ESR 是越小越好，但 本钱稳定性IC 根本电气特性Power Supply RejectionPSRR:also

15、 known as ripple rejection, measures the LDO regulators ability to prevent the regulated output voltage fluctuating caused by input voltage variations. 也被称为纹波抑制，措施的 LDO 稳压器的力量，以防止输出电压波动所造成的输入电压的变化The same relation for line regulation applies to PSRR except that the whole frequency spectrum is consid

16、ered.同样的关系线适用于的 PSRR ，但整个频谱是考虑。PSRR is based on small signals, whereas line transients are large signals.基于小信号，而电压瞬态大信号。PSRR是Very critical in many RF and wireless application 格外关键的在很多射频和无线应用supply rejection in the frequency band between 100 kHz and 1 MHz is especially important in applications where

17、 the output ofa dc/dc switch mode power supply (SMPS) isused to power the linear regulator 抑制频带在 100 kHz 和 1 MHz 的是特别重要的应用场合中的输出的 DC / DC 开关模式电源 SMPS 是用于功率的线性稳压器But why battery-powered application?But why battery-powered application?The output voltage will show a large variation based upon the curre

18、nt drawn from that battery.输出电压将消灭大的变化依据目前从该电池。In GSM, transmit and receive cycles in the RF draw a huge amount of current,causing a large change in voltage on the output of the battery. That change in voltage is seen throughout the system and on inputs to all of the system regulators.在GSM ， 传输和接收周期

19、中的射频吸引了大量的电流，造成一个大的变化对输出电压的电池。这一变化在电压是整个系统， 并投入到全部的系统监管。One of the dominant internal sources of PSRR in an LDO is the bandgap reference. so its important to have a bandgap reference with high PSRR. 其中一个主要的内部来源的PSRR 的 LDO 中的带隙基准。因此，必需有一个带隙基准高的 PSRR 。Board layout must be carefully done to reduce the f

20、eedthrough from input to output via board parasitics.电路板布局必需认真进展，以削减馈从输入输出通过董事会寄生。u Improved Power Supply Rejection For IC Linear Regulators滤波器u LC filterIC 根本 电气 特性 Noiseu 在输出信号中包含我们不需要的信号。PSRR、NOISE 简洁混淆的概念！PSRR 输入变化引起输出的变化，抑制力量NOISE固有特性，和外部无关，主要由芯片内部电阻、晶体管产生。u 衡量 NOISE 的两种式：Spectral 谱线 noise dens

21、ity 密度 a curve 曲线that shows noise (uV/Hz) versus 相对Equipment 设备:frequency 频率,that is,noise spectral density cure spectrum analyzer 光谱分析器.with units uV/Hz plotted over frequencyIntegrated 综合的 output noise spectral noise density integrated over aoutput noise voltage (in Vrms)certainfrequency range and

22、 cantherefore be thought of as the total noise in a specified frequency range.Equipment:True root-mean-square(Rms)meterAbsolute measurement with units uV-RMS(rootmean square)take over a fixed bandwidth真有效值测量 AC / DC，u 噪声源：Reference 重要因素，通过外接 LPF 来减小基准噪声的影响。但电容也不能太大，否则会对启动产生影响。 LPF 的 CUTOFF 频率一般会设在1-

23、500KHzresistor divider 电阻分割器 热噪声 4KTR，要减小噪声，采样电阻的阻值不能取很大。和低功耗要求相冲突，假设噪声是必需考虑的因素，也只有部 分的牺牲功耗。EA -假设是 2 级运放，则低噪声设计，第一级供给大局部的 GAIN。PASS FET调整管虽然占芯片比较大的面积，对 NOISE 的影响不大，由于和其它几个因素相比，PASS FET 缺少了增益级。u 整个环路的频率特性也会对 NOISE 产生影响。是对频域的噪声做积分，噪声的增益大了，所以噪声也会大。所以对于低噪声的设计，尽量承受大的相位裕度。假设可以的话可以在R1 两端并一相位裕度减小，环路趋于不稳定，增

24、益的峰值变大。output noise voltage (in Vrms)个小电容，这样在高频时,基准到输出之间是一个单位增益的放大器。IC 根本电气特性Accuracy 准确性Accuracy:specifies all effects of line regulation ( VLR), load regulation ( VLDR), reference voltage drift (Vo,ref ), error amplifier voltage drift (Vo,a ),external sampling resistor tolerance (Vo,r ), and temperature coefficient (VTC). 指定所有影响线路调整，负载调整，参考电压漂移，误差放大器电压漂移，外部取样电阻宽容，和温度系数。