SN74CBT3345C: -6V on input with low Current

Jim Kotcher

Part Number: SN74CBT3345C

Can a CBT-C part receive a -6V input at 0.2 mA without damaging the part?

Part is 74CBT3345C. Converting a -6V input to a positive voltage using a divider network and a +5V supply. The -6V could come up before the +5V supply. There could also be a resistor failure where only the -6V is input to the device. Current limited to 0.2 mA. The CBT3345C part could be a) powered and enabled, b) powered and disabled, or c) not powered, while -6V is present on the input.

over 2 years ago

0 Clemens Ladisch over 2 years ago

Guru 267180 points

That voltage will be clamped to about −0.7 V. This is allowed if the current is limited to less than 50 mA.

0 Jim Kotcher over 2 years ago

Prodigy 10 points

Is the voltage clamped under all three conditions (a,b,c)?

0 Clemens Ladisch over 2 years ago in reply to Jim Kotcher

Guru 267180 points

It's just a diode; no power supply is needed.

0 Rami Mooti1 over 2 years ago in reply to Jim Kotcher

TI__Mastermind 26383 points

Hey Jim,

Yes all three conditions should be fine as long as your limit the current to 50mA. To reiterate Clemens here, it's just a diode so there isn't some circuitry that requires a power supply to actually clamp this. Limiting the current will keep the device safe from damage.

Thanks,
Rami

0 Jim Kotcher over 2 years ago

Prodigy 10 points

Thank you for the responses.

The input will be clamped to -0.7V. With the device powered and enabled will the output also be -0.7V or is it clamped further?

0 Jim Kotcher over 2 years ago in reply to Jim Kotcher

Prodigy 10 points

The reason I ask is that this device feeds another device that has a minimum voltage requirement.

0 Rami Mooti1 over 2 years ago in reply to Jim Kotcher

TI__Mastermind 26383 points

Hey Jim,

If you're also limiting the current you'll probably have some extra drop from any limiting resistor or circuitry. But the camping itself would clamp it down and should keep it in that 0.7~0.6V level.

Thanks,
Rami

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SN74CBT3345C: -6V on input with low Current