TPS54140: Input voltage at Pin 10 (Vout)

Hi Fabian,

Do you mean to say that the part failed, and there's a short between VIN and PH?

Thanks,

Andrew

Hi Andrew, 

yes the part failed and there is a short between VIN and PH. 

Best regards, 

Fabian

hmm. what's the VIN max that the part sees Is there any protection at the input?

Thanks,

Andrew

Vin max is 24V but in this case VIN max is 10V, Imax is 640mA. 
The input protection (reverse polarity and overvoltage protection) is in the screenshot above.

Hi Andrew, 

The connection from Pin 2 -> 10 is 50-500Ohm (depends on the pcb). One that is still working it is 44MOhm.

I also measured the diode: Pin 10 -> 2 = 0,54V, Pin 2 ->10 = 0,58V (2,17V with a working one) 

Best regards, 
Fabian

Hi,

I'm really sorry I didn't get to this post today. I was busy handling an urgent customer issue.

Thanks,
Andrew

Hi Fabian,

Thank you for sending your concern.

Just to set a baseline, have you conducted an A-B-A part swap between the working IC and the non-functional IC? This can help us determine what is the root cause of the failure whether it be with the part itself or systemic.

Thank you,

Joshua Austria

Hi Joshua, 

for us its not possible to change the TPS54140 by ourself. 
Or do you mean something different?

Best regards, 

Fabian

Hi Fabian,

Yes, I do mean to change the TPS54140 by yourself. 

If this is the case unfortunately it will be difficult to determine a root cause failure. A short between PH and VIN suggests that the HS FET is damaged. This can occur in any number of cases. For example, if there is a case where your input voltage drops but PH is held high for too long, this can cause damage to the HS FET. 

Are there signs of damage on the IC or at any of the surrounding components?

Thank you,

Joshua Austria

Hi Joshua, 

thank you for your answer. 

we try to let it change. 

There are no other signs of damages, I only could measure that the diode  (HS FET) is not working anymore. 
What can cause that the diode brakes? What are the maximum values from the diode? 
Are there other reasons that the HS FET gets damaged?  

Best regards, 
Fabian

Hi Fabian,

The maximum value requirements for the diode should be listed in section 9.2.2.4 of the datasheet.

There could be a number of any other reasons, but as stated above, it may be difficult to diagnose this without knowing if this is a system or device issue. A reverse voltage condition for example could also cause HSFET damage.

Thank you,

Joshua Austria

Hello Joshua,

I meant the diode that is in the HS FET....is it possible to get the datasheet of the HS FET?

We think it is a problem with the TPS54140 as all the protection components are still ok.

If we replace your IC, we still have the problem that the other voltage regulators are also damaged as the input voltage of 10V (Vin) is also on pin 10 (Vout). And this should normally be 4.8V. The regulators after the TPS54140 have 6V specified as Vin_max....

The structure looks like this:
Vin (10V) -> protection components -> TPS54140/ Vout = 4.8V -> step-down -> 3.3V, 1.2V and 1.5V

Best regards, 

Fabian

Hi Fabian,

Unfortunately, I do not believe we can disclose those internal parameters with the customer.

Did you test the suspected TPS54140 on another board to see if it was working correctly? Do you have a potential KGU of the TPS54140 to swap onto the application to see if you are still exhibiting 10 Vout instead of 4.8?

I understand that the other regulators are damaged, but this could help us diagnose what may have occurred in the application to cause a short between VIN-PH. In any case, it could also be helpful to see more of the schematic. Can you also send a larger view of the schematic and all the components connected to the input/output of the TPS54140?

Thank you,

Joshua Austria

Hi Joshua, 

I understand that.

 
We can't change the TPS54140, we can't solder the exposed pad. We don't have any other TPS54140. 

Is it possible to send the schematic to your E-Mail or somewhere else then add it here? 

Best regards, 

Fabian