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LMP2022: LMP2022 interface issue

Jeffrey Lee82
Prodigy 20 points
Part Number: LMP2022

We have a situation where the supply voltage, normally +5V nominal, is off (assume 0V) and the V- pin is connected to ground. There is a series resistance of 14Kohms connected to pin 6 (minus input). There is an input connected to that series resistor that can independently sustain a voltage of -3.9V. My questions are as follows:

  1. Can this induce circuit overstress for input pin 6?
  2. If conduction occurs, how much current can be anticipated coming from pin 6?

I would appreciate assistance on this issue. Thank you.

  • 0
    TI__Guru* 93105 points
    Hi Jeffery,

    The LMP2022 has ESD protection didoes from the inputs to the supply rails. These diodes are off during normal operation. If you apply -3.9 V to the 14 k resistor leading to the inverting input when the supplies are off (assuming they become a high impedance when off), the ESD diode leading from the input to V- may begin to conduct.

    The diode current will be much limited by the 14 k resistor. The diode current will be about (-3.9 V + 0.6 V)/14 k, or about -235 uA. Turning the diode on provides the secondary function of clamping the voltage to the diode forward voltage level. Between the low current and the clamping it very unlikely that the LMP2022 would be overstressed by the application of an input voltage while unpowered.

    Regards, Thomas
    Precision Amplifiers Applications Engineering