去掉LDO的输入电容，LDO的输出纹波反而减小了，这是怎么回事呢？

松哥无敌 · 发表于 2017-4-7 11:17

EDA365欢迎您登录！

您需要登录才可以下载或查看，没有帐号？注册

x

一个LDO，前级加30uf电容，后级30uf电容，后面加载100ma。输入10v，输出5v。这个时候LDO前级纹波在500mv左右，后级纹波300mv左右。把LDO前级的30uf电容拿掉后，LDO前级和后级电压的纹波都很小了，10mv以内，满足设计要求。

超級狗 · 发表于 2017-4-7 23:47

踢哀（TI）文檔

松哥无敌 · 发表于 2017-4-7 11:18

我顶我顶我顶。。。

fengyu6117 · 发表于 2017-4-7 11:25

帮你顶

yjj198709 · 发表于 2017-4-7 17:02

从手册上看：The input capacitor (CIN) compensates for line fluctuation. Using a resistor of approximately 1 Ω in
series with CIN dampens the oscillation of input capacitance.

The device is designed to operate from an input voltage supply range between 4 V and 40 V. This input supply
must be well regulated. If the input supply is located more than a few inches from the device, TI recommends
adding an electrolytic capacitor with a value of 47 μF and a ceramic bypass at the input.

你前面的电容是贴片的陶瓷电容么？要不试下47uf电解电容？看到上面需要ESR接近1ohm的。