LMP8640: Output behaviour when Rload < Rsense

user6458113

Prodigy 30 points

Part Number: LMP8640
Other Parts Discussed in Thread: INA293, INA281

Using Spice model found on the forums, the output decreases as the load is decreasing around and below Rsense.

Hereafter is the simulation schematic and a plot at Rload=Rsense:

The component limits seem not reached.

Is there something I missed about this component ?

Regards

over 4 years ago

0 Javier Contreras4 over 4 years ago

TI__Mastermind 32700 points

Hello JY,

Where did you obtain the LMP8640 model? Can you share it with me.

0 user6458113 over 4 years ago in reply to Javier Contreras4

Prodigy 30 points

Hello Javier,

I found it there: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/772374/lmp8640-pspice-model/2865354#2865354

What I don't understand is that the common mode voltage is specified from -2 to 42V, but it seems it does not work properly near 0V.

0 Javier Contreras4 over 4 years ago in reply to user6458113

TI__Mastermind 32700 points

Hello JY,

I think the issue with the model is the CMRR at the voltages below. I also tried the simulation and the IB Vs VCM is not modeled and could cause additional error not seen in the model. There is a much higher IB when the VCM is below 2.1V and that is why there are some issues when VCM is close to 0V.

May I suggest you use the INA293 or the INA281. They do not have the same issue of High IB at that VCM.

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LMP8640: Output behaviour when Rload < Rsense