TL331: operation when VCC=0

Michael T Schneider

Expert 3780 points

Part Number: TL331

What is the unpowered operation of TL331 with input voltages applied?

Assume single power supply configuration.

VCC : turned off

VCC- : GND

IN+ and IN- : signal voltages present

over 4 years ago

0 Paul Grohe over 4 years ago

TI__Mastermind 49906 points

Hi Michael,

The inputs can be taken up to 36V even with 0V on the supply. Obviously, it will NOT be functioning (output state may be incorrect!) and this is NOT a specified mode of operation.

Leakage currents will be in the upper pA to sub nA as the input devices B-E junctions are reverse biased.

We recommend that there be series resistance on the inputs to limit any current should things get out of hand. 1k Ohm per volt is recommended.

Please see the following Appnote for more information:

Application Design Guidelines for LM339/LM393/TL331 Family Comparators

0 Michael T Schneider over 4 years ago in reply to Paul Grohe

TI__Expert 3780 points

so the output state is in-deterministic during this condition?

0 Paul Grohe over 4 years ago in reply to Michael T Schneider

TI__Mastermind 49906 points

Hi Michael,

With Vcc=0V, there is no power for the device to function internally.

So the output will be high-impedance (the output is a NPN transistor, and if there is no base voltage, it will not conduct). So the output will be "high" regardless of the input voltages.

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TL331: operation when VCC=0