LM5176: UVLO hysteresis current flows thru upper resistor

Ella KIM

Part Number: LM5176

Hello,

May I know why UVLO hysteresis current flows thru the upper resistor? I was thinking it should flow thru lower resistor to ground.

-Ella

over 2 years ago

0 Brigitte over 2 years ago

TI__Guru 65200 points

Hello Ella,

It would make more sense having it dependent on the upper resistor as this is in general the bigger one and therefore you get easier more hysteresis. It would surprise me if the formula is wrong as a lot customer are using it, but give me some days to clarify this.

Best regards,
Brigitte

0 Brigitte over 2 years ago in reply to Brigitte

TI__Guru 65200 points

Hello Ella,

I checked in the lab and the formula is right.

Best regards,
Brigitte

0 Ella KIM over 2 years ago in reply to Brigitte

TI__Expert 4212 points

Hi Brigitte,

I also think the formula in datasheet is right. My customer is just wondering why. Intuitively, the current should flow lower resistor but the formula includes upper resistor.

-Ella

0 Brigitte over 2 years ago in reply to Ella KIM

TI__Guru 65200 points

Hello Ella,

The current is flowing through the lower resistor, but the upper resistor defines the current that is coming from VIN, so it defines the hysteresis caused by the current through the lower resistor.

Best regards,
Brigitte

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LM5176: UVLO hysteresis current flows thru upper resistor