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TPS62933: TPS62933 lock with no output

Hale Tan
Expert 3770 points
Part Number: TPS62933

Hi team,

When use tps62933 to convert 5V to 3.6V to power the measurement board (average power consumption 10mA) and display board. The terminal board, measurement board, and display board are powered on normally, and the 3.6V output is normal. During normal operation, unplug the measurement board, and the 3.6V output is still normal; at this time, remove the measurement board. When connected, the 3.6V output becomes 0V, the power consumption of the whole machine is 260mA, and the power consumption becomes larger. When the power is turned off and on again, the 3.6V output is normal, and the power consumption of the whole machine is normal. After unplugging the measurement board, the 3.6V output is still 0V, and the power consumption of the whole machine is abnormal again.

It seems that the current limit is triggered, but i am not sure that why the power consumption is 260mA. And we tested the inductor current as below when unplug/plug the measurement board:  

 

Could you help make sure if the device has been limited? And if so, what method can we try?

By the way, the measurement board has about 800uF capacitor, if the customer remove the capacitor, tps62933 can work all the time whenever unplug the measurement board.

  • 0
    TI__Genius 16632 points

    Hello Hale,

    1. Could you please provide schematic for us review?

    2. How to look at your IL waveform as it's voltage channel? What's the convert ratio? Did they measure negative IL? Please capture Vin/Vout/SW/IL waveforms with 800uF Cout VS without 800uF Cout.

    3. The 800uF Cout is really large, could have big inrush current during startup. Could you reduce to tens of uF?

  • 0 in reply to Miranda Gu
    TI__Expert 3770 points

    Hi Miranda,

    The schematic is as below and the input voltage is changed to about 5V.

    The indictor current is tested with a resistor about 0.5ohm.

    Is there any possibility that the device can be locked by some condition and unlocked by power up again? What condition may be the reason? And 800uF is essential for the customer application. 

  • 0 in reply to Hale Tan
    TI__Genius 16632 points

    Hello Hale,

    Did they use differential probe to measure the voltage drop on 0.5ohm? If not, using one non-differential probe cannot get right IL value. Please provide right Vin/Vout/IL/SW waveforms for our analysis. 

    Have you checked the loading condition? Is it possible that the loading drags Vout down? Please disconnect the loading, using an external loading to check whether the issue caused by loading. 

    Besides, is your Vin 5V or 15V? 5V is your description, but 15V is on your schematic. If Vin is low, please look at EN resistors and EN-pin voltage, maybe device haven't been enabled. You can float EN-pin to enable the device.

  • 0 in reply to Miranda Gu
    TI__Genius 16632 points

    As the case moved to offline discussion, I will close this thread.