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TPS3808G33 functionality and

Bhupendar Singh
Prodigy 100 points
Other Parts Discussed in Thread: TPS5430

Hi,

We are using 2  TPS3808G33 in our Board one to Monitor 3.3V rail and other to monitor 18V@3A rail using voltage divider (Consist of 10k and 2.26k to make it 3.3).

Wanted to check with you if we need to put any series resistance to Sense pin of TPS3808G33 for current limit/protection. If yes what value we should use here?

Is it ok to use TPS3808G33 to montor 18V@3A ?

  • 0
    TI__Mastermind 32350 points

    Hi Bhupendar,

     

    As far as understand in your application, the chosen resistor values (10K & 2.26K) for your voltage divider is much smaller than the 4Mohm of the internal voltage divider resistor of the SENSE pin for a fixed voltage version.  Thus the leakage current is negligible and does not affect the threshold voltage accuracy. I am not sure how you power up your Vdd from the 18V rail, because the maximum Vdd voltage is 7V. And you are not suppose to connect your Vdd to the SENSE pin.

    for more info here is an app note attached.

     

     

    Thanks!

    Tahar     

    slva450[1].pdf
  • 0 in reply to Tahar Allag
    Prodigy 100 points

    Hi We are not driving VDD through this 18V rail. We have 3.3V on our board, generated through TPS5430 reg which is providing VDD to TPS3808G33. 

    My concern was on the current limitation side or avoiding damage to TPS3808G33 on Sense pin side as it is used to sense 18V through voltage devide.

    But as there is internal voltage devider used, the top resistance of internal voltage devider will come in the series of the  sense pin input, so i think it doesn't require external series resistance for current protection. Please confirm if otherwise.

     

     

    Thanks & Regards

    Bhupendar

  • 0 in reply to Bhupendar Singh
    TI__Mastermind 32350 points

    Hi Bhupendar,

     

    If you are setting up your circuit as shown the attachment, then you are doing it right. Also it is good to add 1 to 10 nf bypass cap on SENSE input to reduce sensitivity to transients and layout parasitics.

     

     

     

    Thanks!

    Tahar