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TPS25946: Not shutting off when EN/UVLO is low

Cameron Nichols
Prodigy 30 points
Part Number: TPS25946

Hi Team, 

We are observing an issue with the TPS259461L. 
We are using it as switch for controlling output power to a daughter board.

The setup:
Input power is derived from a DC power supply - set at 7.4V with 10A limit. 
The output power is connected to a DC programmable load - set at CC of 5A, and being turned on/off manually.

The control of the eFuse is from a microcontroller (which drives the EN/UVLO high/low, and an external 100K PD is also attached to the pin)
Additionally, there is a 7.5K PD on  the OVLO pin. 

What we are observing is that when we turn on the eFuse, and then load it with 5A, and then subsequently turn it off, the output remains conductive. 
The EN/UVLO pin and OVLO are both low.

Toggling the EN/UVLO pin has no effect, however tripping over-current or driving OVLP pin high causes the eFuse to switch off as expected.


We cannot figure out why the eFuse won't swtich off when EN/UVLO is driven low. 
Any help on this matter would be appreciated. 

Kind Regards

  • 0
    TI__Guru* 79181 points

    Hi Cameron,

    Do we have some waveforms? Let me check more on this and get back.

    Regards

    Kunal Goel

  • 0 in reply to Kunal Goel
    Prodigy 30 points

    Hi Kunal

    I am getting our technician to bond some wires so I can capture the waveforms. 
    I have also swapped the part for the TPS259814L on some of the units and haven't been able to replicate the issue.

    Am I correct in understanding that for both devices, toggling EN/UVLO should reset the device as long as the fault has cleared?
    (i.e. if TSD triggered, or ILIM pin short) then EN/UVLO below SD threshold should trigger reset?

    If OC is triggered (<SC) I have noted that I cannot reset the device without power cycling it.

  • 0 in reply to Cameron Nichols
    TI__Guru* 79181 points

    Hi Cameron,

    Am I correct in understanding that for both devices, toggling EN/UVLO should reset the device as long as the fault has cleared? YES

    (i.e. if TSD triggered, or ILIM pin short) then EN/UVLO below SD threshold should trigger reset? YES

    If OC is triggered (<SC) I have noted that I cannot reset the device without power cycling it. Which device?

    Regards

    Kunal Goel