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tps54620 no output when loaded

Francois
Prodigy 40 points
Other Parts Discussed in Thread: TPS54620

3441.regulators.pdf

On the attached file are my regulators. I use them to supply my components on the PCB.

I supply the Regulators with +5V (D5V0P). With the +3V (D3V0P) there are no regulation. +5V in +5V out when measured with a multimeter. I would like to know why.

The regulators output, including the +3V, switches of as soon as I put a load, even as low as 10mA, on the output of the regulator.

On the 0.95V regulator I draw a maximum of 350mA. On the 1.8V regulator I draw a maximum of 280mA. On the 2.5V regulator I draw a maximum of 20mA. on the 3V regulator I draw a maximum of 3A. 

I would like it if anyone have a solution for my problem. The components is 4 of 10 that I bought on the same order. I should think that they would come from the same batch.

  • 0
    TI__Guru**** 191445 points

    The TPS54620 should regulate with no load.  The first thing I would do is remove the resistor divider from Vin to EN and GND.  It looks like your start voltage is set to 5.2 V.  After that check the PH node voltage with a scope and see if the devices are switching.  Let me know what you find.  Please post waveforms if you can.

  • 0 in reply to JohnTucker
    Prodigy 40 points

    I have removed the resistor divider from EN. The regulators except for the 3V regulate with no load. I have checked the PH node voltage and it is switching. Unfortunately I can not attach any waveforms. When a load is attached to the regulator outputs, the voltage drop to 0V.

  • 0 in reply to JohnTucker
    Prodigy 40 points

    Anything else I can try with this problem.

  • 0 in reply to Francois
    TI__Guru**** 191445 points

    Without seeing waveforms it is difficult to guess.  How many boards do you have that show this problem out of how many total?  Where are teh input capacitors located relative to the IC pins?  they should be as close as possible.  When you apply the load, does VIN drop below the UVLO?  Do you have any solder defects or wrong value components?