一个power问题！

szx841129 · 发表于 2011-12-10 13:33:22

马上注册，结交更多好友，享用更多功能，让你轻松玩转社区。

您需要登录才可以下载或查看，没有账号？注册

x

有个FPGA的小板，本来应该出来2.5V的电压，但是不知道为什么，出来的一直是2V，为什么呢？
请看下图：

jackzhang · 发表于 2011-12-10 14:18:04

最好把你的电源部分原理图发上来

szx841129 · 发表于 2011-12-11 21:28:44

回复 2# jackzhang

szx841129 · 发表于 2011-12-11 22:00:00

我用LTspice对电路做了一个简单的simulation，负载用的是3Ω的电阻，请参看下图：

szx841129 · 发表于 2011-12-11 22:03:57

对于fset pin,datasheet里面这样说：The LTM4601 is designed to typically operate at 850kHz
across most input conditions. The fSET pin is normally left
open or decoupled with an optional 1000pF capacitor. The
switching frequency has been optimized for maintaining
constant output ripple noise over most operating ranges.
The 850kHz switching frequency and the 400ns minimum
off time can limit operation at higher duty cycles like 5V to
3.3V, and produce excessive inductor ripple currents for
lower duty cycle applications like 20V to 5V. The 5V and
3.3V drop out curves are modifi ed by adding an external
resistor on the fSET pin to allow for lower input voltage
operation, or higher input voltage operation.

还有，用3Ω的电阻作为负载是否合适？