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TPS92682-Q1: Unable to output 4A current - Schematics review

PYTsai
Genius 11825 points
Part Number: TPS92682-Q1


Hi team,

Can you help review our schematics attached below ?

We have a TPS92682 design with the following design conditions

Vin = 9~16Vdc

CC mode

Iout = 0~4A with 5 ohm load

Currently, it can output 2A normally, but the MOSFET and DIODE components are both at 100°C.

When the output current is set to 3A via the SPI command, the actual output current is only around

1A. We checked the FLT1/FLT2 registers and found that when the output current is insufficient,

CH1UV, CH1UC, and CH1ILIM will be detected. In the ILIM register, we set VILIM(THR) = 250 mV.

Could you please help me figure out what the problem might be? 

1.jpg

Thanks 

PY Tsai

  • 0
    TI__Expert 6050 points

    Hi PY,

    Your device is likely hitting current limit. Can you please post the following wave forms?

    Inductor current
    Switch node voltage
    Input voltage
    Output voltage


    This is what your scope shot should look like, the channels are labeled in the picture and I need the same time division:




    Best,
    Daniel Louis

  • 0 in reply to Daniel Louis
    TI__Expert 6050 points

    Has your issue been resolved?

  • 0 in reply to Daniel Louis
    Prodigy 10 points

    Hi Daniel,

    We don't have a current probe, so we can't provide the inductor current waveform.

    The correct current output waveform is as follows.

     

    When the circuit is set to 3A output, it fails to output normally, and the waveform is as follows.

    Details are shown in the following figure.

       

     

    Thank you

    Jason Huang

  • 0 in reply to Jason Huang
    TI__Expert 6050 points

    Hi Jason, 
    It's hard for me to properly diagnose the issue because I dont have the inductor current wave form. However, I see the customer set the current limit to be 4A which may not be enough at the 3A set point. Please increase the current limit and see if that helps maintain normal operation. 

    The "flickering" is happening because the device is encountering some sort of fault and is trying to reset itself. Can you please read the fault register during this event?

    Best,
    Daniel