TI中文支持网Part Number:TPS61378-Q1
Below is the schematic that used TPS61378-Q1 as the regulator to output 5V. The input voltage is 3.3V and use an external MOSFET to switch on or off this power input.
The regulator cannot start up even with light load(0.1A). Please see the waveforms showed below. The first one is the startup waveform with no load and the second one is the startup waveform with light load(0.1A).
CH1-SW
CH2-VO
CH3-Inductor current
If the OUT pin is connected to the VO pin and remove C4802(2U2) on OUT pin, the regulator can start up with 0.57A load current.
I find that there is a MOSFET between the HS FET and load to cut off the path between input side and output side during shutdown.
Why this MOSFET would prevent the regulator start up with light load. It seems that if the regulator is enabled but FB voltage is below 0.1V for some milliseconds, then the regulator will shut down, after that the regulator will try again.
Johnsin Tao：
HI
建议你先用芯片网站的在线仿真webench确认一下电路。
0.1A负载启动出现异常，空载启动正常吗？ 更大的负载（>0.1A)启动也出现异常吗？
如果是这样，注意输入电容尽量靠近功率电感，功率电感饱和电流足够，功率回路尽量小。
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Mark Dai：
Hello
当把电子负载切换到电阻负载时，500mA负载电流下，能够正常启动，但在600mA下，还是不能。
layout是按找datasheet中推荐的布局布置的。
可以帮忙解释下在重载情况下，为什么内置的switch会阻碍regulator的正常启动。
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Johnsin Tao：
Hi 如上，带载能力下降，建议确认： 电容尽量靠近功率电感，功率电感饱和电流足够，功率回路尽量小。
重载下异常，一般过载保护导致的，而上面提到的都影响过载保护。
