LMR23625: How does the protect when Vout connect to a external power source?.

Junshi Shimeno

Part Number: LMR23625

Dear Team,

I am designing circuits using LMR23625.

My circuit has a external power source and the output is connected to Vout of LMR23625.
When Vin=0[V] of LMR23625, Vout(+5V) voltage of LMR23625 is 5[V] by the external power source.
1. Can I insert Diode(Dadd) in the attachment diagram for protect of LMR23625?.
2. Is there a problem about LMR23625 when there is not the diode(Dadd) ?.
3. Is there the method to recommend to protect for LMR23625?.

Best regards

Junshi

over 5 years ago

0 Ethan T over 5 years ago

TI__Expert 3835 points

Hi Junshi,

This is a possible solution to protect from an external power source, but will decrease your efficiency. Make sure the FB trace is after the diode and output capacitor so that the converter takes into account the diode drop.

Thanks,

Ethan

0 Junshi Shimeno over 5 years ago in reply to Ethan T

Prodigy 30 points

Hello Ethan,

Thank you for your reply.

Is the decrease in efficiency caused by the voltage descent of the diode?
Is the diode necessary to follow LMR23625? .

Best regards,

Junshi

0 Ethan T over 5 years ago in reply to Junshi Shimeno

TI__Expert 3835 points

Hi Junshi,

That is also an option, but there will be a forward voltage drop at the output. I also forgot to mention that if the diode is within the control loop, forced PWM operation is not possible since it does not allow negative current.

Regards,

Ethan

0 Junshi Shimeno over 5 years ago in reply to Ethan T

Prodigy 30 points

Hello Ethan,

Thank you for your reply.

I understood that the option could not use force PWM mode.

Can I insert the Diode bitween the output capacitor and the FB trace for allow negative current from output capacitor ?.

best regards,

Junshi

0 Ethan T over 5 years ago in reply to Junshi Shimeno

TI__Expert 3835 points

Hi Junshi,

I believe this is a probable solution. I would just make sure that the device is not on while the external power source is also on since it can possibly affect the control loop.

Thanks,

Ethan

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LMR23625: How does the protect when Vout connect to a external power source?.