TPS40170: HDRV and LDRV of TPS40170 are no working

Hi,

When you startup/EN the part, do you see the SS capacitor (C15) voltage ramped up?

Thanks
-Arief

thanks for the answer. I measure it and it was ramping up and down.

i will change the value tomorrow but i guess the value only affect the stability and was not supposed to affect the the output of PWM (LDRV or HDRV). why shall i remove C17? how did you get those value for C18, C20, R11, C19 and what are the condition for it?

will really be delighted if you can explain it

Thanks
Willy

this is the voltage at SS pin. Actually it ramps up to 2.56V and down to 240mV and according to datasheet it shall be an overcurrent fault restart. what shall i change in that case? my PGOOD is always 0V

Hi,

Yes, you can double check whether there is a short anywhere in the circuit.
Also for the value of stability, you can download a calculator on this page
www.ti.com/.../toolssoftware

At the bottom, there is a software section and in there i believe there is an excel calculator

Thanks
-Arief

ok thanks I saw the software and have being using it, but I am getting with the value you calculate a phase margin of 11°C and the one I was using was given me a phase margin of 49°C.
<i have been looking for short, but i did not find any.

Could we please go offline, because I am struggliung to get the problem fix by friday.? have you try to call me?

Hi,

now changing my bootstrap capacitor, i can HDRV(yellow line) is trying to switch but the Gate of the High side swithc is having enough energy to switch on. my SS pin (blue) is not more ramping up and down, he is instead ramping and stay constant at about 1,25V and not 3,3V.

Could the proble being my MOSFET having enough Gate Capacitor which does not enable his switching? would be delighted to get an answer today.

Have you removed C17 from your circuit? This is the capacitor on your low side MOSFET

Thanks
-Arief

Hi,

i already remove C17 and change the value of the compensator. I even change the value of Bootstrap-capacitor because a wrong value was mounted.

Is the part still not switch properly?

Also, try to increase the RLIM value and see if it changes its behavior

start increasing the RLIM, i just remove it. Interesting is that I am having 5V Output but the converting is really hot, the LOW Side FET ist not switching. The high side FET is switching but in linear interval and the FET is also too hot.

as Conclusion no PWM on LDRV. HDRV is having a PWM but with only 5Hz switching frequency. the voltage is only 6.4V and going from 4.87V to 6.4V (see the picture)

Hi,

Is the FET damaged? I would try with a 2nd board if there is one with new FET or new TPS40170 .
You can also measure the impedance of the LDRV and HDRV and compare with new unit and see if there is a damaged there.
I also noticed that you dont have much of the thermal pad on Q1, if i am comparing it with the EVM

You also need to put the input capacitor closer to the FETs such as the one in the EVM, the loop between HighSide FET, Low Side FET and GND should be tight like this one on the EVM. 

Thanks