SN74LVC1G126-Q1: About voltage application to input terminal when VCC = 0V

Takuya Nagasawa

Part Number: SN74LVC1G126-Q1

Hi TI-team

I have a question about input / output protection when the power of SN74LVC1G126-Q1 is turned off.

If a voltage is applied to the input terminal when VCC = 0V, will the IC be damaged?

The data sheet says "Ioff Supports live insertion, partial-power-down mode, and back drive protection"
I think it's okay because the application report (Logic in Live-Insertion Applications.) Says "Ioff protection circuitry ensures that no excessive current is drawn from or to an input, output, or combined I/O that is biased to a specified voltage while the device is powered down.".
However, I checked it just in case because the explanation of the data sheet only mentions "This device includes circuitry to disable all outputs when the supply pin is held at 0 V. When disabled, the outputs will neither source nor sink current, regardless of the input voltages applied." (because the protection of the input terminal is not specified).

Best Regards,

Takuya Nagasawa

over 2 years ago

+1 Clemens Ladisch over 2 years ago

Guru 243180 points

The description of I_off mentions only the outputs because the inputs are overvoltage tolerant in all cases, even when powered. See [FAQ] Can the input voltage (Vi) to my logic device be higher than the supply voltage (Vcc)?

+1 Michael J Schultis over 2 years ago in reply to Clemens Ladisch

TI__Mastermind 24485 points

Hello,

Yes, Clemens is correct here. Providing the FAQ link, since his link didn't come through: https://e2e.ti.com/support/logic-group/logic/f/logic-forum/723607/faq-can-the-input-voltage-vi-to-my-logic-device-be-higher-than-the-supply-voltage-vcc

For devices with Ioff, when the supply is down, another VCC can be applied to the inputs without damage as long as it doesn't exceed the datasheet rated voltage limits.

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SN74LVC1G126-Q1: About voltage application to input terminal when VCC = 0V