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1、IC基本电气特性Quiescent current 静态电流Standby current低功耗电流Dropout voltage 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电源排除/抑制NoiseAccuracy精确性IC量测ICLDO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;Volta
2、ge 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 低缺点：效率低、如果需要冷却设备,则要求较大的空间IC基本电气特性Quiescent Current & Standby CurrentQuiescent Current:The difference between input and output.Low quiescent current is necessary t
3、o 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 by a shutdown signal.Quiescent Current and Output CurrentThe value of quiescent current is mostly determined by the series pass element, topologies, ambient tempe
4、rature, 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 传统的三端稳压器如：LM78#Vdrop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 1.62.5VNPN Vdrop=Vsat+Vbe 0.9VPNP Vdrop=Vsat 0.150.4VPM
5、OS 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 resistance. 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
6、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 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
7、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 most 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
8、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
9、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.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,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 condit
10、ions. 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, 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
11、 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 Increasing 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 ResponseIC基本电气特性Transient Re
12、sponseu Transient Response:the maximum allowable output voltage variation for a load current 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 capacitor value , the ESR of the output capacitor, the buypass capacitor , and the maximum load-current . 瞬态响应是一
13、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 loop 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 L
14、DO 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 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
15、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 spectrum is considered.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.PSRR是基于小信号,而电压瞬态大信号.Very critical in many RF and wireless application非常关键的在许多射频和无线应用supply rejection in the frequency band between 100 kHz and 1 MHz is especially important
