LM2991: Output Voltage

user4638730

Prodigy 100 points

Part Number: LM2991

Hi,

I am using LM2991 with Vin = -5V, Vout = -2V, Iout = 0.3Amax now.

However, to fix the problem, I need to use the LM2991 Vout at -1.55V.

When I refer to the data sheet, Vout is typ -2V, but there is no value for min.

Since Vref = -1.21V, I think it is possible to output Vout = -1.55V, is that correct?

I think of R2=750ohm and R1 = 2.7kohm. And my circuit current is 40mA min, so minimum load is no problem.

Regards,

Ikuo

over 3 years ago

0 Stephen Ziel over 3 years ago

TI__Mastermind 33625 points

Hello Ikuo,

There is nothing obvious in the datasheet which indicates to me that you cannot use this device down to the reference voltage for the output voltage. It appears that -1.55V would be fine given your conditions. Still, datasheets back as far as 1994 listed this -2V minimum in their datasheets. You may want to test this to confirm that you can achieve -1.55V.

Thanks,

- Stephen

+1 user4638730 over 3 years ago

Prodigy 100 points

Hello Stephen-san,

Thank you for your reply.
I will confirm and use it as you recommend.

Regards,

Ikuo

Power management

Power management forum

LM2991: Output Voltage