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TPS2456: output abnormal

user5129062
Intellectual 295 points
Part Number: TPS2456

The schematic as below，We have a 1second switch test，that means switch from Channel A to channel B, work for 1 seconds, and then switch back to Channel A.In the process of switching back, we found that MOSFET Gate could not be drived.The waveform as below.Please help us analyze it,thanks

  • 0
    TI__Expert 5940 points
    Most probable is a current limit fault due to Cout charge and loading present. Expand the P12_Aux, look at Vin, Vout, Vfault timer, I-in (for the P12_Aux channel). The timer is probabaly timing out and the Gate may be in regulation mode.

    Brian
  • 0 in reply to Brian Daugherty
    Intellectual 295 points
    Hi ，
    Is there any risks if the fault rimer（CTX） design too long ？
    thanks
  • 0 in reply to user5129062
    TI__Expert 5940 points
    Yes, there is a risk. Set the timer max to the current the FET can survive (from its SOA curve) at full Vin. This is the worst case current/voltage/time (i.e. Energy in Joules) the FET can sustain without damage during a power up into short condition. The DS SOA curve is for 25C die temp. You must derate as die temp is higher. For instance if the steady state die temp (max) = 80C, then derate the current numbers in the FET DS by (150-80)/(150-25) for a FET rated at 150C operation.

    Brian
  • 0 in reply to Brian Daugherty
    Intellectual 295 points

    Hi Brain，

      I have a issue when the load on the back end is large，The INA is PSU，the INB is battery，when the battery volatge below 11.8V，the load current is 14A，the switch is abnormal，waveform as below，I don't know why the GAT1A open again when the battery is discharging， please help to analyze it，thanks

  • 0 in reply to user5129062
    TI__Guru** 102571 points
    Hi,

    Please help with more waveforms to analyse. During this transition, probe
    1. For INA channel: GATE voltage of Hot-swap FET, input current of INA, voltage at CTA, output voltage
    2) For INB channel:
    a) GATE voltage of Hot-swap FET, input current of INB, input voltage, output voltage
    b) GATE voltage of Hot-swap FET, input current of INB, voltage at CTB, output voltage
    3) input current of INA, input current of INB, output voltage, GATE voltage of Hot-swap FET of INA.

    Regards,
    Rakesh
  • 0 in reply to Rakesh
    Intellectual 295 points
    Hi Rakesh，
    It's difficult for us to measure current，is it possible to measure the voltage only ？