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Original question:

TPS76901-EP and Q1, Set to 3V3 as per procedure but I get 3V0.

TPS76901-EP: TPS76901-EP and Q1, Set to 3V3 as per procedure but I get 3V0.

Jon Page
Prodigy 20 points
Part Number: TPS76901-EP

There seems to be an ongoing discrepancy with the reference voltage specified for this part, or we have been supplied with a very old part.

A colleague calculated the feedback resistors for a 3.0V output using this device, ironically using an old data sheet dated May 2001, the reference voltage he used was 1.224V, he calculated R1 at 348k and R2 at 240k, measured voltage 2.98V which is correct. When I checked his calculations, I used the datasheet from your website which is dated December 2009,  page 8 specifies the feedback voltage as 1.127V, using this and the resistor values given above the output should measure 2.76V, it does not. The part fitted has the marking PCFI, does this indicate is we have been supplied old stock? My concern is that in the future we will receive new stock and the resistor values will then be wrong.

Any guidance is appreciated.

  • 0
    TI__Mastermind 20045 points
    Hello Jon,

    Sorry about the confusion. Can you confirm that you are using the -EP version? I just want to make sure you didn't accidentally get a regular version (TPS76901) or automotive version (TPS76901-Q1) of the part. These datasheets are the ones that specify the 1.224V reference. I will look in to if the -EP version actually is intended to have a different Vref or if this is just an error in the datasheet.

    Thanks,
    Kyle
  • 0 in reply to Kyle Rakos
    Prodigy 20 points
    Hi Kyle,

    I had specified the EP version however I’m beginning to have doubts that this was fitted, the part carries the marking PCFI which looks like it is a TPS76901DBV the EP version should be marked PCFS if I am understanding things correctly. I apologize if I have wasted your time, I should have checked this first.

    Best regards,
    Jon
  • 0 in reply to Jon Page
    TI__Mastermind 20045 points
    Hello Jon,

    Yes, it looks like the PCFI indicates the standard TPS76901 part as opposed to the TPS76901-EP version. No worries about the question. Hopefully that got you the answer you needed! If not feel free to follow up again.

    Thanks,
    Kyle