LM74930-Q1: low temperature -30℃ boot failed, LM74930 can't open mosfet and no power output

Hi Wang,

Is the controller working fine other than FET not turning ON?

Can you share waveforms with the following signals probed during power up.

VIN,VS,HGATE,VCAP

Regards,

Shiven Dhir

here is the waveform under -25℃, as you can see, VS(in yellow) and VCAP(in red) are all low, in this case, HGATE(in green) can't open,  and power input VIN(in blue) is normal.

As the temperature rises up to 10℃, the circuit can recover itself and attached the normal operation under 10℃.

attached the recovery process, as you can see, the temperature rising up to 10℃, everything is back again, and LM74930 can work well.

Hi Wang,

Can you try reducing the R12784 from 10k to 4.7k and test again?

Regards,

Shiven Dhir

Sure, by the way, could you please give me some additional advice so that I can try everything together tomorrow?   I‘ll do this test at a 3rd party laboratory,   thanks in advance.

so do you think VS current too small?   how many mA does VS need?  is it equal to I(cap) from 1.3mA to 2.7mA?

I found the designer made a mistake with R12784, it is a NTC 10k Resistor,  maybe it's the root cause,  it's so ridiculous.

I'll test it again, thank you Shiven.