LMZ14202H: Inrush Current Spike

Hi Emanuel,

Thank you for using our products. Would you please share your schematic?  How to you control the startup, by applying the input source, or the input voltage is stable and you just pull up the EN pin? And, how big is your Cin?  Can you monitor the VIN pin voltage and Vout at the same time along with this inrush current?

Thanks,

Youhao

No problem Youhao,
I will make measurements and will post them.
Meanwhile here is the schematic.

Hi Emanuel,

From the schematic, I can tell that the startup is actually the bus applications, and there would be inrush to charge those input capacitors.  Since there is also an input inductor, there may have resonance between the inductor and Cin if C10 does not provide adequate damping.  Note that such inrush is not controllable by the IC because it happens before the IC starts to work.

If the inrush is an issue, you may consider to employ an thermistor as a simple inrush limiter, or elegantly use a Hotswap or inrush limiting device. Take a look at the following link: https://www.ti.com/power-management/power-switches/efuse-hotswap-controllers/products.html

Thanks,

Youhao

Hi Youhao,
Indeed it looks like the spike occurs before the IC starts to work, but it is hard to imagine that a small 47uF capacitor is able to genrate a 11A for 100mS spike.
I will try to repeat the test with C10 removed.

Please let me know the status of your test.

Thanks,

Youhao