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INA190: Output current

Dominic Bernath
Prodigy 20 points
Part Number: INA190

Hi

I am using the INA190 to drive the input of a sigma delta ADC with built in MUX. This means that the ADCs MUX switches to the built in capacitor (of 25pF) and the INA190 has to provide the current. I am optimizing the time for the INA190 to settle and with SPICE simulations and verifications on hardware have seen that loading the output of the INA190 with a resistor improves the settling time. Now I have two questions:

1) Can you confirm that this is a good method for decreasing the settling time when the INA190 has to drive a capacitive load of 25pF which is attached and detached by a MUX? Are there other recommended ways?

2) What is the maximum resistive load the INA190 can drive? The datasheet only mentions a R_L of 10kOhm as test conditions. 

Thanks

Dominic

  • 0
    TI__Mastermind 18780 points

    Dominic,

    Great questions. Thanks for using E2E!

    1. Yes, this is a good method for driving a capacitive load. The reason for the faster settling time is that you are adding more resistance to the the output impedance of the amplifier to help isolate the amplifier from the capacitive load. There is more information about how this works here. 

    2. The maximum output current is given by the claw curves in figures 12 and 13 of the datasheet. There is a great video here that discusses how to interpret these curves. 

  • 0 in reply to Carolus Andrews
    Prodigy 20 points

    Quick follow up: 

    Through spice simulations we tested several options. 

    We have achieved the best results with a snubber (capacitor with resistor in parallel). Faster settling times and less overshoot than only adding a resistive load to the output of the opamp. 

    Further references: