LM62435-Q1: Can the BIAS pin be higher than VIN?

Matthew Trescott

Part Number: LM62435-Q1
Other Parts Discussed in Thread: LM25148

Hello,

I want to supply the LM62435's BIAS pin from an external 5 V regulator. However, sometimes this external regulator will be on when the LM62435's VIN is off; i.e VIN=0 V and BIAS=5V. Is this supported?

Another part I plan to use (the LM25148) doesn't allow an external bias greater than VIN, but for the LM62435 it looks like it would be OK based on the datasheet and a quick diode-check with a multimeter. But I'd like to make sure.

Thanks!

Matt

over 1 year ago

0 Joshua Austria over 1 year ago

TI__Mastermind 24115 points

Hi Matt,

After taking a look at the datasheet, I cannot find anything that says that this would be an issue. I do see that the datasheet recommends connecting this to output voltage, but the only thing I found for an external power supply is to ensure that the voltage entering the BIAS pin does not rise above 16 V.

If it helps, I did find that the PIN FMA for the LM61435 does state that an external supply for BIAS is ok up to 16 V and should exhibit normal operation without any stipulations with VIN. These two parts have similar structures.

Thank you,

Joshua Austria

0 Matthew Trescott over 1 year ago in reply to Joshua Austria

Prodigy 20 points

Hi Joshua,

Thnaks! That is helpful to know. I will check on a test board and update this post soon.

Kind regards,

Matt

0 Joshua Austria over 1 year ago in reply to Matthew Trescott

TI__Mastermind 24115 points

Hi Matt,

Sounds good!

Thank you,

Joshua Austria

0 Matthew Trescott over 1 year ago in reply to Matthew Trescott

Prodigy 20 points

I tested it and indeed, no measurable current flows into BIAS when VIN is not supplied. When VIN is supplied and there is a load on the output, BIAS draws ~183 μA.

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LM62435-Q1: Can the BIAS pin be higher than VIN?