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TPS25840Q1EVM-079: TPS25840Q1EVM-079 defective

biketart
Prodigy 110 points
Part Number: TPS25840Q1EVM-079
Other Parts Discussed in Thread: TPS25840-Q1

hi,

im only posting as ive been instructed to to get confirmation of a defective evaluation board and a totally inadequate user manual.

details:

Case details or comments:

i have been delived a faulty eval kit order number T01613178. TPS25840-Q1 Evaluation Module.
the Fault pin no 24 of the TPS25840, which is open drain does not go low in the fault condition. it sits at ~ 3.6V at all times, even though the buck converter has shut down.

ive been at this for 25 years, and dont want to waste ages on this. Repalcement please asap.

Bruce.

  • 0
    TI__Expert 5000 points

    Hi Bruce,

    Not sure for your fault situation, it is for OV or OC, and do you use external FET in this case? Could you please supply detailed comments? 

    Best Regards,

    Ethan Wen

  • 0 in reply to Chuqiang Wen
    Prodigy 110 points

    development kit is used as supplied with external fet. check your TI schematic on the user manual.

    12v input supply. its the overcurrent fault condition.

    i checked the pull down led and resistor. Since the fault pin is supposed to be an open drain output for the fault pin, when i pull the pin low externally the led (led2) lights up, just about as the series resistor (r18) is far too big at 10K??

    should be more like 1k, sink you have up to 10mA sinking current on Fault pin. Vcc is present @ 4.99v.

    Im testing the over current with a Rigol DL3021 DC electronic load, it triggers the OC condition @ 3.3A, as per the Eval kit setup.

    But as said before the fault pin just sits at 3.6v. It cant sink the current for the D2 & R18 pull down load.

  • +1 in reply to biketart
    TI__Expert 5000 points

    Hi Biketart,

    For the series resistor to LED, the resistor is using for limiting LED current. The res value is up to the LED brightness you want to set and the power consumption of res. 

    The fault phenomenon you measured is correct. If use external FET and source current from VBUS, fault pin won't be pulled down when OC occurred. 

    Thanks!

    Best Regards,

    Ethan Wen

  • +1 in reply to Chuqiang Wen
    Prodigy 110 points

    Ethan,

    thanks for getting back.

    i know how a resistor/LED pull down works..

    here's an image form the user guide - it exsplicitly says that the led turns on in a fault condition (it does not mention disabling the external FET) - this manual needs a lot of editing and lacks any useful onformation. please remove it or edit it asap.

    If TI cannot be professional enough to write a correct and useful manual for an evaualtion kit, they should not sell it.

    Thanks,

    Bruce.

  • 0 in reply to biketart
    TI__Expert 5000 points

    Hi Biketart,

    All these features are detailed in datasheet. The main goal of user guide is the reference for validation. 

    Rgards,

    Ethan Wen