TPS548A20: 57K ossilation after load step

Relay Man 2

Part Number: TPS548A20

Hi,

I am trying to use the above part. 5V to 1V when I do a load step I get about 150mV P-P oscillations at about 57KHz on the output and this becomes continuous. There is 180uf of ceramic capacitance directly on the output and then via a zero ohm link a further 70uf of ceramic capacitance and 700uf of tantalum capacitance.

What is the best way of curing this?

over 3 years ago

0 David_Daniels over 3 years ago

TI__Genius 16760 points

I am unsure of your inductor value, switching frequency, tantalum esr or the mode pin setting.

But here some suggestions for improving stability

The mode pin can be configured to adjust an internal ramp. Try changing Rmode using value in the table 3.

Also, if you using a feedforward capacitor across the high side feedback resistor remove it.

If you have an oscilloscope plot of the output voltage and schematic you can share please attach.

0 David_Daniels over 3 years ago in reply to David_Daniels

TI__Genius 16760 points

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TPS548A20: 57K ossilation after load step