SN74LV594A: Could I wire pin 3 "QD" to ground directly event this pin is at output high situation, VCC=P3V3

JH Wu

Part Number: SN74LV594A

Normally, I use a program to control the pin 3 "QD" that is connect to a NAND gate 74LVC1G08GW.

For ICT, we would like to control the NAND gate directly, so we would like to know if it may damage SN74LV594APWR if we wire the pin 3 to ground directly?

9 months ago

0 Albert Xu1 9 months ago

TI__Mastermind 23015 points

Hi JH,

This should be no problem. Any unused inputs and/or outputs can be wired directly to ground.

0 JH Wu 9 months ago in reply to Albert Xu1

Prodigy 30 points

Hi Albert,

Thanks, so we don't need to add a small resistance that is less than 10 ohm to avoid damage SN74LV594APWR internal buffer, right?

+1 Clemens Ladisch 9 months ago

Guru 265760 points

Unused outputs that are active should not be shorted to the opposite voltage level; this will exceed the absolute maximum rating of 25 mA.

You are likely to need more than 100 Ω to prevent damage, depending on the supply voltage. I would use 1 kΩ to be safe.

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SN74LV594A: Could I wire pin 3 "QD" to ground directly event this pin is at output high situation, VCC=P3V3