LM5060: LM5060 cannot work as expected

Hi Kevin,

Welcome to E2E!

In the first case, the device turns ON the GATE when Vin crosses the UVLO threshold. After that Vout follows the Vin. It is as excepted.

For the other two cases, Can you please include VIN, VOUT, GATE and Timer voltages in a single scope shot and share us to understand 

Regards

Rakesh

Hey Rakesh

thanks for your replay.

here are two pictures which indicate all the VIN VOUT GATE and Timer, It gives me the feeling that the Gate voltage cannot reach to higher than VIN if the voltage is 27v? while the Gate's voltage is higher than VIN when the input voltage is only 12v

Thank you

What is the load ? Timer starts for overload event

Best regards 

Rakesh

Hey Rakesh

I think the problems was caused by those two big 100uF capacitors connected to the output pins of this chip(my previous schematic shows that two 100uF cap).

After i remove it, then things becomes normal. However I don't quite understand why on it, as the charge current is definitely not high after power up for those two cap to trigger a over-current fault?

I also find out if the input voltage decreased to around 20v, then it's normal with my current hardware configuration. Pretty weird 

You are correct. once it is powered up the inrush should not lead to overcurrent fault. Can you probe the current and check ? 

hey Rakesh

if inrush is the issue, do you know how to address it?

I tried to limit the current from power bench, and I did not find out any inrush higher 0.5A, so it really confused me.

Hi Kevin,

Please add capacitor on GATE to limit inrush current (refer Figure 26 C3 capacitor slows down the GATE ramp rate)

Can you probe the current and share the test waveform? 

Hey Rakesh

yes, after I add the cap, problem solved. I will do more test for it.

I find out it would be hard to probe the current, but I do find out the peak current for VIN can reach up to 2A(I figured this out by see my over-current LED from power bench turned on and off immediately) after I add this cap. is that normal?  

before I add this. the LED will not blink. which is of course as the output didnot work yet.

I put the power bench to constant current mode and tuning the peak current until when I plug in the connector to my hardware, I find out around 2A, it will not blink. but any value lower  than 2A, it will blink. So I guess the peak current after I add the cap is 2A.  

Hey Rakesh

I will try to figure out how to probe the current, while before I close this thread, 

Just want to get some feedback from you on where I should add the cap. 

should I add the cap to the Gate pin of LM5060 or the Gate pin of the mosfet, as you can see there are resistor(R38) between them,.

my test shows that both of them are ok. but the value may differ a little bit based on the location that the cap located. I guess it's because the resistor have the impact?