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TPS54526: No Output Voltage

Anand

Intellectual 540 points

Part Number: TPS54526

Hi TI,

We have designed TPS54526 based 5V DC-DC regulator in our board.I couldn't able to generate 5V output.All the other pins function as expected (EN is high, and VREG5 produces 5.5V).When probing the output, the 5V was observed only for around 100ms and then it decays rapidly.Kindly help me to resolve this issue.

over 5 years ago

0 Neal Zhang over 5 years ago

TI__Expert 4720 points

Hi,
Could you please provide the SW and Vo waveform? Do all the board behave the same?

0 Anand over 5 years ago in reply to Neal Zhang

Intellectual 540 points

Hi Zhang,

We have build two boards.In both the boards observing same issue.

I have attached waveform for your reference.

0 Anand over 5 years ago in reply to Anand

Intellectual 540 points

Hi Zhang,

We have tried with different feedback resistor combinations where i could see the output voltage only till 4.49V.

0 Neal Zhang over 5 years ago in reply to Anand

TI__Expert 4720 points

Hi,
From your waveform, it seems the Vin is only around 4V. Could you check the VPWR_IN?

0 Anand over 5 years ago in reply to Neal Zhang

Intellectual 540 points

Hi Zhang,

The input voltage is proper 12v at VPWR_IN.

0 Jason Wang (BSR-MV) over 5 years ago in reply to Anand

TI__Genius 9550 points

hi Anand,
Vin ramps up is too slow which trigher the Vout UVP.
Suggest:
improve Vin ramp up slew rate
Or
increase R1 to 1M ohm

0 Anand over 5 years ago in reply to Jason Wang (BSR-MV)

Intellectual 540 points

Hi Wang,

I tried with R1-1M Ohm for enable.I couldn't see any improvements.For your information I'm feeding supply from regulated DC power.

0 Neal Zhang over 5 years ago in reply to Anand

TI__Expert 4720 points

Hi,

Please change C11 to 0.1uF.

0 Anand over 5 years ago in reply to Neal Zhang

Intellectual 540 points

Hi Zhang

Now regulator is working after 0.1uF change for soft start pin.

Thanks for your valuable suggestion.

0 Neal Zhang over 5 years ago in reply to Anand

TI__Expert 4720 points

You're welcome. The problem reason is "Vin ramps up is too slow which trigger the Vout UVP" as Jason said.