LM5176: LM5176 output voltage during FB circuit failure

mutoh kenji

Part Number: LM5176
Other Parts Discussed in Thread: LM51770, LM51772

If the LM5176's FB pin fails and is pulled to GND,
it will likely continue to boost the output voltage.
I would like to confirm the output voltage at that time.

Input: 12V
Output: 12.8V (RFB1: 20k, RFB2: 300k, L1: 5.6uF, RT: 23.2k)

1. To what voltage will the output voltage rise?
1. Is this the result of some kind of protection function?

Thank you in advance.

2 months ago

0 Stefan Schauer 2 months ago

TI__Guru 61481 points

Hi Mutoh,

thank you for using the E2E forum.

When the FB at the LM5176 is shorted to GND there is no further output voltage protection available and the device would go to max duty cycle boost mode.

FYI:

The LM51772 or LM51770 would have an separate OVP which is independent from the FB pin

Best regards,

Stefan

0 mutoh kenji 2 months ago in reply to Stefan Schauer

Prodigy 20 points

Thank you for your reply.

What is the maximum duty cycle of the LM5176?
Is it possible to calculate the maximum duty cycle?

Thank you in advance.

0 Stefan Schauer 2 months ago in reply to mutoh kenji

TI__Guru 61481 points

Hi Mutoh,

unfortunately we have not specified this parameter in the datasheet.

Best regards,

Stefan

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LM5176: LM5176 output voltage during FB circuit failure