TPS7A49 - Voltage sag under any load

Michael Chapman78

Other Parts Discussed in Thread: TPS7A49

I've designed a power supply using the TPS7A49 and am experiencing a drop in voltage under any load.

The power supply implementation is using the recommended circuit design with feedforward capacitor, and an output voltage of 22.9V.

At no load the voltage is spot on at 22.9V, but when I start applying a load (1.6mA draw) the voltage drops to 22.88, and continues to drop to 22.3V at 130mA.

Any thoughts or ideas would be greatly appreciated.

-Mike

over 7 years ago

0 David Hopkins over 7 years ago

TI__Expert 8905 points

Hi Mike,

There will be some drop in Vout as Iout increases due to load regulation (see figure 17 in the datasheet).

For drop that is more than expected make sure you are measuring the output voltage at the top of the feedback resistors - if you are measuring the output voltage at the load there is likely some resistive (I x R) losses due to board parasitics.

Regards,
David

0 Michael Chapman78 over 7 years ago in reply to David Hopkins

Prodigy 20 points

Thanks for the reply.

I looked into the IC and discovered that the FB pin has been damaged.
Replacing the IC fixed the issue.

0 David Hopkins over 7 years ago in reply to Michael Chapman78

TI__Expert 8905 points

Hi Mike,

Thanks for the update and good to hear!

-David

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TPS7A49 - Voltage sag under any load