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INA146: what is the max input voltage when no power is connected to the IC

Part Number: INA146

Quick question:

INA146, the data sheet doesn't spec the max input voltage when no power is provided to it. Does anyone have info on that?

Thanks!

DC

  • David,

    Most datasheets specify only performance of the part under normal operating conditions and lists absolute maximum rated conditions in order to avoid damaging the part.  To understand what will happen under unpowered conditions, you need to understand simplified ESD/EOS protection scheme of INA146 as shown below.

    "No power is provided" may mean two different things; supplies are floating or supplied are at the system ground.  If the supplies are floating, all pins are floating and you may put any voltage on any single I/O pin but NOT on two pins or more.  For example, you may put 1000V on Vin+ and all pins will follow.  However, if for example, Vin- is connected to ground, the current will flow thru EOS1 diode (see above) and the maximum voltage allowable on Vin+ would be 200V so the maximum input current does not exceed: Iin_max=200V/200k=1mA.

    If on the other hand the supplies are tied to ground and you apply voltage to either input pin, the current will flow thru ESD1 or ESD2 (see above) and thus the maximum input voltage that may applied is 100V (Iin_max=100V/100k=1mA).