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INA190: input pin voltage range in bidirectional current measurements

Part Number: INA190
Other Parts Discussed in Thread: LMP8640

Dear Support,

I am using the INA190 for high-side bidirectional current measurements. According to the datasheet and other notes appeared on E2E (see for nistance https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/971909/ina190-how-to-achieve-bi-directional-current-measurement?tisearch=e2e-sitesearch&keymatch=ina190#) , I set GND = -2.5V, Vs = +2.5V and Vref = GND.

Unfortunately, the device is largely asymmetric in terms of input voltage, going from (GND-0.2V) to +40V. In my high-side setup, that means I can measure the current drawn from a negative supply limited to -2.5V - 0.2V = -2.7V This limit is more-or-less confirmed by bench results (INA reaches  -3.5V than stop working).

Is there a way to have a large negative common mode voltage? I would like to measure current from a supply in the range from -20V to +20V. Should that be not possible, can you suggest me how to power and/or configure the INA to measure current from negative supply in the range -40V to 0V or even -20V to 0V ?

Thank you in advance for your support.

Best,

Alberto

  • Alberto,

    You are correct. While biasing ground to a voltage <0V will provide a small amount of headroom for even lower negative common mode voltages, this will not allow you to get down to -20V. 

    There are a few options for common modes this low:

    1) you could use one of our devices rated for this low of common mode voltage, such as the LMP8640. This only goes down to -22V however.

    You could try to pedestal the voltage down using something along the lines of TIDA-00313. This uses zener diodes and transorbs to effectively level the part down to this voltagem and the common mode will shift in reference as well.