• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Subscribers 62 subscribers
  • Views 285 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2663: Reverse current /FLT behavior

Jason Morris
Prodigy 80 points
Part Number: TPS2663


Hi, the datasheet is not clear on whether the reverse current fault is latched or not. I'm having a problem with a latching fault, which occurs when other e-fuse devices fed from the same source power up after the TPS2663. The power source droops by a couple of hundred mV while the new device turns on, and existing TPS2663 allow a small amount of current back from the load. I don't need reverse flow protection as such, but it triggers the /FLT output and remains latched. The datasheet (page 8, electrical characteristics) shows a thresholds V(revth) & V(fwdth) which would indicate that a reasonable amount of forward current would be needed to clear the fault. All other faults self clear, but this one requires a substantial amount of 'normal' to go away: with the nominal 30mOhm Pass Fet on resistance, it would need around 2 amps to clear the fault?

  • 0
    TI__Guru** 106201 points

    Hi Jason,

    Thanks for reaching out!

    Once the device triggers reverse current fault and turns OFF the FET, the forward voltage drop has to cross V(fwdth) threshold to turn back ON and start conduction. That is V(IN_SYS) - V(VOUT) > V(fwdth) has to be met, that means either V(IN_SYS) has to increase or V(OUT) has to drop to turn ON the device. 

    Best Regards,

    Rakesh

  • 0 in reply to Rakesh
    Prodigy 80 points

    Ok - so there's really a trap to be aware of - this is labelled as a 0.6 - 6A adjustable e-fuse; but in the case of any momentary reverse current (that may be acceptable at low limits), the fault that is generated can't be cleared until greater than 2 amps is passed in the forward direction (30mOhm x 2A >= V(fwdth) ). Also - I believe your comment about turning the FET off only applies to an external blocking FET; the internal one still stays on with reverse current (which can be ok...).

  • +1 in reply to Jason Morris
    TI__Guru** 106201 points

    Hi Jason,

    I got your point.. enough current (2A) has to follow in the ON device to meet V(IN_SYS) - V(VOUT) > V(fwdth) so that the parallel device, which was in reverse OFF state to get forward biased. 

    you mentioned.. The power source droops by a couple of hundred mV while the new device turns on, and existing TPS2663 allow a small amount of current back from the load.

    It looks like the supply droop while new device truns ON is triggering reverse condition. Can you increase decoupling capacitance at the input of eFuse to help.

    Also - I believe your comment about turning the FET off only applies to an external blocking FET; the internal one still stays on with reverse current (which can be ok...).

    yes.

    Best Regards,

    Rakesh