IC基本电气特性-华为内部员工培训资料Word文档下载推荐.doc

1、NoiseAccuracy精确性IC量测IC（LDO）结构框图Capacitor电容 reference参考（电压）error amplifier误差信号放大器Pass element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 反馈网络 Series-pass Element无源元件（二极管）优点：简单、输出纹波电压低 、出色的 line 和负载稳压、对负载和 line 的变化响应迅速 、电磁干扰 （EMI） 低缺点：效率低 、如果需要冷却设备，则要

2、求较大的空间IC基本电气特性Quiescent Current & Standby CurrentQuiescent Current（Ground current）: The difference between input and output。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 Current:The input current drawn by a regulator when the output voltage is disabled

3、by a shutdown signal.Quiescent Current and Output CurrentThe value of quiescent current is mostly determined by the series pass element, topologies, ambient temperature, etc. 静态电流的值主要是一系列无源元件，拓扑结构，环境温度等 确定的具体特性与IC结构、制程密切相关IC基本电气特性 Dropout Voltage（特有规格）u Low-Dropout Linear Regulators低压差线性稳压器 u 传统的三端稳

4、压器如：LM78xxVdrop的典型值是2V，看到很多7805应用 时都会背着一个散热器。LM317 2V LM1117 1.2V。u 调整管采用的结构 LM317 输出 Darlingtong Vdrop=Vsat+2Vbe 1.62.5V NPN Vdrop=Vsat+Vbe 0.9V PNP Vdrop=Vsat 0.150.4VPMOS Vdrop=Io X Ron 35350mvNMOS Vdrop=Vsat+Vgs 1Vu 不同调整管结构的比较：1 The NMOS pass element is most advantageous due to its low on resist

5、ance. Unfortunately, the gate drive difficulties make it less than ideal in applicaitons and as a result there are few NMOS LDOs available. 传统上，PNP双极型晶体管应用到低压线性稳压器，主要是因为它很容易实现了低压降电压。2 Traditionally, the PNP bipolar transistor has been applied to low dropout applications, primarily because it easily

6、enables a low drop out voltage. However, it has a high quiescent current and low efficiency, which are not ideal in applications where maximizing efficiency is a priority. 然而，它的高静态电流和低效率，这是不理想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 levels exceeding mos

7、t bipolar devices. PMOS上设备已经高度发达，现在的性能水平超过最双极器件。u Dropout voltage：the input-to-output differential voltage at which the circuit ceases to regulate against 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规范对进一步削减输入电压;这一点时发

8、生的输入电压接近输出电压。 Vds=Vo-Vin IC基本电气特性Efficiencyu The efficiency of a LDO regulator is limited by the quiescent current and input/output voltage as follows: 效率是有限的LDO稳压器的静态电流和输入/输出电压如下：输入电压降低;u 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

9、，电压和辍学静态电流必须减少到最低限度IC基本电气特性Load Regulationu Load Regulation:A measure of the circuits ability to maintain the specified output voltage under varying load conditions. 衡量电路的能力，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

10、, increasing dc open-loop current gain improves load regulation. 负荷调节是有限的开环电流增益的系统。正如上述方程，增加直流开环电流增益改善负载调节。u Line Regulation:a measure of the circuits ability to maintain the specified output voltage with varying input voltage. 衡量这条赛道的能力，保持指定的输出电voltage.open环电流增益改善负载调节。其中， Rds为调整管Q1源漏等效电阻。u Increasi

11、ng dc open loop current gain improves the line regulation. 提高直流开环电流增益提高了线路调整Output Voltage With Respect to Input VoltageLine Transient Response IC基本电气特性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

12、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 capacitor 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 lo

13、op bandwidth. ESR is the voltage variation resulting from the presence of the ESR of the output capacitor. ESR is proportional to ESR.凡 t1闭环带宽。 esr是电压变化造成在场的情况下的ESR的输出电容器。 esr成正比esr。Transient Response of LDO Regulator瞬态响应LDO稳压器u 输出电容的影响ESL load-transient response负载瞬态响应 ESR load-transient responseESL

14、 影响比较小，但不合适的PCB布线同样使得性能下降。ESR是越小越好，但 成本稳定性IC基本电气特性 Power Supply Rejectionu PSRR:also 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稳压器的能力，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