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TPS60111 ENABLE pin

Andy Peters
Genius 3945 points
Other Parts Discussed in Thread: TPS60111, TPS2061

The datasheet for the TPS60111 regulated charge pump tells us that "ENABLE high may only be applied when VIN is inside the recommended operating range." Also, every diagram in the datasheet show ENABLE driven by a discrete.

So the obvious question: is it OK to simply tie ENABLE to VIN? Obviously when the input voltage to the device is first applied, it will be out of the recommended operating range for a millisecond or so depending on capacitance.

I'm pretty sure that it's safe but when data sheets indicate "don't do this" I tend to take the warnings seriously.

Thanks.

  • 0
    TI__Guru**** 169156 points

    A voltage should not be applied on ENABLE unless VIN is first applied to the IC.  You should be able to tie ENABLE to VIN without damaging the IC; however, ENABLE hi and low are specified relative to VIN so the IC's exact startup time may be unpredictable if VIN ramps slowly.

  • 0 in reply to Jeff F
    Genius 3945 points

    Jeff F said:
    A voltage should not be applied on ENABLE unless VIN is first applied to the IC.  You should be able to tie ENABLE to VIN without damaging the IC; however, ENABLE hi and low are specified relative to VIN so the IC's exact startup time may be unpredictable if VIN ramps slowly.

    OK, I see. The input to this guy is coming from a TPS2061 switch, which will only switch after its input side is stable. The VIN therefore should take about a millisecond to reach full value; dunno if that's "slow," although the start-up time basically doesn't matter, as long as it starts up.

    Thanks for the info.

  • 0
    TI__Expert 6060 points

    Andy,

    Connecting VIN and ENABLE together will not damage the device.

    We found a problem with the device not starting up properly under certain operating conditions (especially low temp), when ENABLE high is applied before VIN is within recommended operating range.

    Therefore we recommend to drive ENABLE high after VIN is within the recommeded operating conditions.