LM2937: Is an external diode needed from OUTPUT to INPUT?

Kazuya Nakai59

Guru 21565 points

Part Number: LM2937
Other Parts Discussed in Thread: LM317

Hello guys,

One of my customers asked me whether an external diode is needed from OUTPUT to INPUT for LM2937.

They found an external diode was connected from OUTPUT to INPUT on page 10 of LM317 datasheet.

Could you please tell me whether the external diode is needed or not in LM2937 case?

Your reply would be appreciated.

Best regards,

Kazuya Nakai.

over 7 years ago

0 Ryan Eslinger over 7 years ago

TI__Guru 55940 points

Hi Kazuya Nakai,

The external diode is recommended for LM317 in order to protect the LDO from reverse current through the NPN pass transistor.

LM2937 has a PNP pass element and therefore has additional inherent protections for reverse current. As such the diode is not needed for the LM2937.

Very Respectfully,
Ryan

0 Kazuya Nakai59 over 7 years ago in reply to Ryan Eslinger

Guru 21565 points

Hi Ryan,

Thank you very much for your reply. I understood it.

Best regards,
Kazuya Nakai.

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LM2937: Is an external diode needed from OUTPUT to INPUT?