以上两幅图分别来自TI的SLVA453和SLVA905,之前我理解的D-CAP2是在D-CAP1的基础上发展而来,D-CAP2可以使ESR小的陶瓷电容然后增加内部ramp电路到FB,但是以上这两张图让我很疑惑,这两种模式有啥区别?
Star Xu:
For D-CAP2 mode converter, it is recommended to use ceramic capacitor with low ESR. Electrolytic cap has higher value and high ESR. If you use electrolytic cap, the side effect could be on the control loop. For D-CAP1 mode, the high ESR capacitor will contribute to higher output ripple, which can be used for ramp compensation for the control loop. Different from D-CAP1, D-CAP2 mode control combines constant on-time control with an internal compensation circuit for pseudo-fixed frequency and low external component count configuration with both low ESR and ceramic output capacitors. It is stable even with virtually no ripple at the output. An internal ramp is added to reference voltage to simulate output ripple, eliminating the need for ESR induced output ripple from D-CAP1 mode control.
Johnsin Tao:
回复 Star Xu:
hI再电感上增加电容电阻网络实际上是获取纹波然后注入到反馈,因为DCP1模式要求输出要用一定纹波。或者你需要ESR相对较大的输出电容也是可以的。而DCAP2就没有这样的限制,输出可以直接用低ESR陶瓷电容。我印象中是这样的,但是你给的CAP2是乎也增加了纹波注入,或许你选哦详细看一些这些电路的说明。
ting zeng:
回复 Star Xu:
您说的是区别,但是为啥我给出的两张图,你们官方的资料里的一会D-CAP一会D-CAP2,输出都是陶瓷电容的例子,图几乎没区别 确叫不同的名字
ting zeng:
回复 Johnsin Tao:
同样的架构,你们官方的资料里的一会D-CAP一会D-CAP2,输出都是陶瓷电容的例子 小的陶瓷电容
Vental Mao:
DCAP是在电感上跨界RC采用ripple
DCAP2的RC是设计在芯片内部,外部不用在电感上跨接RC