TPS59621: TPS59621 OCP at -40°C

Hello, 

Can you send a waveform and schematic?
Best,
Ryan

Please have a look at the attached waveform.  In this case Channel 1(yellow) is PGood from the TPS59621, Channel 2(Blue) is the 1.1 Volt VDDC voltage and Channel 3(Red) is system reset.  I am also uploading a PDF of the circuit.  Thanks!

3386.Sheet4.pdf

Hello, 

How many devices do you see have this issue, and what is the ratio of working to non-working parts? If you haven't, could you try ABA swap with another new device? Does it only fail at -40 C or is there a temperature where it won't have this issue? Can you provide the same waveform, but with the device working?
Best,
Ryan

We have around a 75% failing rate at -40°C.  We have tested around 60 of the units so far.  We are currently working on changing the parts with newer ones from a different lot.  We do not have a way of verifying the components at the chip level.  If we take a failing card and run it off of a bench top supply we know that configuration works.  I am attaching an image from a different card showing these 3 signals.  This was done at a tighter timescale.  If it is needed I can take this measurement again.  

Do you have spice models for the TPS 59621?  I downloaded PSpice for TI but it does not seem to be in the included libraries.  Thanks!

Hello,

Does this work at other temperatures with the same fail ratio?

Unfortunately, we do not have a PSPICE model for this part. 

Best,

Ryan

They only really fail at -40.  Almost all cards work just fine at room temperature.  The cards that fail at -40 will start working again once you warm them up.  The ones that fail will usually start working somewhere between -35°C and -10°C.

Hello, 

Do you mean they will start to work when the IC, the board, or both are warmed up? Is this only happening on one board or across all boards?
If this issue persists, we can have the part sent in for testing. 
Best,

Ryan

Hello,

Any recent activities on this post? Please let me know and I will take over the support.

Regards

Good Afternoon,

Sorry for the delay on the response here.  As we have dug into the issue more it seems to be related to the power sequencing and how the TPS59621 comes on in relation to another supply.  We are making a modification to overcome this issue.  In relation to that, do you know what the input impedance is for pin 35 (VR_ON).  Thank you so much for you continued support.

Hello,

The VR_ON leakage current, at 3.3V, is 8uA min and 25uA max. Please let me know for further support or close the thread as resolved if your question is answered.

Regards