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TPS3808: Vit tolerance

Aaron Spaete
Expert 4527 points
Part Number: TPS3808
Other Parts Discussed in Thread: , TPS3890, TPS3890-Q1

Team,

My customer has the following inquiry:

"I’d like to use the TPS3808G01 in a new design to monitor a 1.5V supply rail. I cannot use the TPS3808G15 because my minimum supply voltage is 1.425V. (It’s supplying a Microsemi A3P1000) The datasheet for the TPS3808, section 7.5 states a Vit tolerance of bormal operation, setween  2% and -2%. My supply voltage may drop to 1.474V in no I can’t accommodate that window of 4%. Could I ask you just how might parts be distributed in that  2% to -2% range? If it’s a Normal/Gaussian distribution, then might I expect a better accuracy in reality?"

Is there a better part we should be using?

Regards,

Aaron

  • 0
    TI__Genius 12630 points
    Aaron,

    1. TPS3808G01 is adjustable with external resistors. This device can monitor 1.425V or any voltage above the VIT threshold for this device which is 0.405V. The TPS3808G01 has +/- 2% accuracy that follows normal Gaussian distribution and the main factors to be closer to typical are Temperature and VDD operating voltage. If you are at room temp and near the middle of the VDD operating range (around 3.3V) then you will most likely be close to typical.

    2. There are a commercial version (TPS3808) and an automotive version (TPS3808-Q1) which slightly different threshold options. I recommend checking both versions to see if something other than the adjustable -G01 will work. For example, what about TPS3808G09 (0.9V rail monitoring - actual threshold is 0.84V), TPS3808G12 (1.2V rail monitoring, actual threshold is 1.12V), TPS3808G125 (1.25V rail monitoring, actual threshold is 1.16V), or the TPS3808G15Q (automotive version monitors 1.5V rails with actual threshold at 1.4V).

    3. TPS3890 is a more accurate device with all the same functionality at TPS3808. The TPS3890 offers +/- 1% MAX accuracy over all temperature and VDD operating range. The TPS3890 and TPS3890-Q1 offer slightly different thresholds than TPS3808 as well.

    I recommend using TPS389015, this is the commercial version of TPS3890 for 1.5V rails. The actual threshold on the falling supply is 1.44V so your minimum supply voltage of 1.425V is low enough to trip the /RESET since this is under 1.44V.

    Let me know if you have any other questions or need any additional support. Thanks!

    -Michael