LMP8640: IN+/IN- voltage when power up

Robin Liu

Part Number: LMP8640
Other Parts Discussed in Thread: INA281

hi team,

as my customer use LMP8640 to sense the NVDIMM P12V power, they find, when the LMP8640 is powered up by a +5V/0V, their is a about 1.375V volts on the IN+/IN- pin, when the Vbus is not present(I mean the Rshunt is not powered by external source).

Could I know if the 1.375V is normal? if so, could you please share me the reason? maybe a block diagram for the internal amplifier?

And if so, could I know if all our current sense devices are like this? if some one can block such a volt like a bias voltage? Thanks!

regards,

Robin Liu

over 2 years ago

0 Javier Contreras4 over 2 years ago

TI__Mastermind 26485 points

Hello Robin,

This is due to the input bias current of the device. Since the input pins normally require some input bias current the voltage depending on you application and how you float your inputs. You can see that on the LMP8640 that at lower voltages it does require a bit more bias current and that is where it settled.

I would recommend trying the INA281 as I think these would be a better option in general.

0 Robin Liu over 2 years ago in reply to Javier Contreras4

TI__Intellectual 1330 points

hi Javier,

Thanks! customer asked, if we have p2p solution with LMP8640 to replace?

0 Javier Contreras4 over 2 years ago in reply to Robin Liu

TI__Mastermind 26485 points

Hello Robin,

The INA281A is pin to pin. The NC pin is not there. If better accuracy is required then the INA293A. Make sure you use the "A" pinout option

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LMP8640: IN+/IN- voltage when power up