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Original question:

TPS7B7702-Q1: VOUT will exceed 9V during start up

TPS7B7702-Q1: VOUT keeps on when there is inverse current during startup

wang wan
Prodigy 130 points
Part Number: TPS7B7702-Q1

Hi,

   From datasheet, we know that "Each time the LDO switch is enabled on the rising edge of the EN pin or during the exiting of the thermal shutdown, the short-to-battery detection occurs. At this moment, if the device detects the short-to-battery fault, the LDO switch is latched off"

We want to the the time between ‘EN’ pulled high and the short-to-battery detection. Because when we pull EN high and pull VIN low, VOUT still keeps on. Does it mean detection circuit is not ready？

  • 0
    Prodigy 130 points

    Correction: We want to know the the time between ‘EN’ pulled high and the short-to-battery detection

  • 0 in reply to wang wan
    TI__Mastermind 42355 points

    Hi,

    I'm not sure that we have data to answer this question directly, but what I can tell you is that the 'scope shot you posted does not show a condition that the device will detect as a short-to-battery event. The short-to-battery detection only triggers if the output voltage is greater than or equal to the input voltage. Please try shorting 12V or greater to the output to test the short-to-battery detection. Note that shorting greater than 12V may instead trigger the reverse current detection circuit, so it will be best to short 12V to the output to ensure that you aren't actually observing the reverse current detection.

    Regards,

    Nick

  • 0 in reply to Nick Butts
    Prodigy 130 points

    We test it again. And we are sure VOUT is greater than the input voltage.However the LDO is still not latched off. 

    Below are the test steps:

    1. Power VIN up to 12V

    2. Power VOUT up to 9V

    3. Add heavy load to VIN for a short time and VIN is pulled down to 7.8V

    4. LDO is not latched off

  • +1 in reply to wang wan
    TI__Mastermind 42355 points

    Hi Wan,

    The reverse current detection trips when there is enough reverse current through the channel; it may be that the reverse current was not enough to trip the circuit because the range of currents that trip the circuit is pretty wide:

    Can you share your test schematic?

    Regards,

    Nick