SN74LVC1G34 output behavior during power-on

George Hong

Other Parts Discussed in Thread: SN74LVC1G34

I've observed that the SN74LVC1G34 output strongly tracks its VCC during power-on, until VCC crosses its power-on threshold. It takes quite a small pull-down resistance to prevent this power-on "glitch". Is this expected behavior? Thanks.

over 14 years ago

0 Chris Cockrill over 14 years ago

TI__Mastermind 46480 points

This can be normal. When Vcc is at 0V the I/O's are high impedance so they may float then. during the power up the output may rise with vcc until the part turns on at about 1V for LVC.

0 George Hong over 14 years ago in reply to Chris Cockrill

Prodigy 70 points

To be clear, the output is not just floating up as VCC rises. It is sourcing current, and it takes a lot of current to pull it down. Is it normal behavior for the output to be driving strongly (not high impedance) during power-on?

0 Chris Cockrill over 14 years ago in reply to George Hong

TI__Mastermind 46480 points

Have you tried tying a pulldown on the input?

0 George Hong over 14 years ago in reply to Chris Cockrill

Prodigy 70 points

Are you suggesting that the output can actually interpret the input as VCC ramps up from 0V (before 1.5V)?

0 Chris Cockrill over 14 years ago in reply to George Hong

TI__Mastermind 46480 points

LVC normall turns on about 1.2V however the LVC little logic is newer process that may turn on lower. some of out other little logic parts begin to work at .5V.

I have no data either way but its worth a try.

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SN74LVC1G34 output behavior during power-on