74lvc2g14

AWG

Hello,

Under normal operating conditions the 74LVC2G14 is supplied witch 3,3V an the Input toggles between 0V and 5V. What happens if the 3,3V Supply is disconnected from the 74LVC2G14 and the Input toggles between 0V and 5V anyway. Can the 74LVC be destroyed?.

thanks,

Andy

over 9 years ago

0 Emrys Maier over 9 years ago

TI__Guru* 96591 points

Andy,

I would like to get a minor clarification -- is the Vcc pin being physically disconnected (Vcc floating) or is the power just being turned off and Vcc = 0 V?

The 74LVC2G14 has the Partial Power Down function (aka Ioff), which means that when Vcc = 0 V, the output can be up to 5.5 V and the maximum current in/out of the device will be 10 uA.

The short answer is: if Vcc = 0 V and an input is applied <= 5.5 V, then the device will be fine.

0 AWG over 9 years ago in reply to Emrys Maier

Prodigy 170 points

Thank you for the quick answer.

In my circuit, it is possible that the VCC pin is floating. This is not the normal mode, but it can be.

0 Emrys Maier over 9 years ago in reply to AWG

TI__Guru* 96591 points

Andy,
It is possible that having Vcc floating could cause problems. I don't have the answer as to what would happen exactly right now, but I will be doing some tests in the lab.

0 AWG over 9 years ago in reply to Emrys Maier

Prodigy 170 points

Ok, so I'm waiting for your test results.

Thank you.

Best regards.

Andy

0 Emrys Maier over 9 years ago in reply to AWG

TI__Guru* 96591 points

Andy,
I haven't forgotten about you. I'm working on getting samples of the 74lvc2g14 to complete my tests. Hopefully I will have them in by the end of the week.

0 Emrys Maier over 9 years ago in reply to AWG

TI__Guru* 96591 points

FYI - I have parts here and will be testing today. I will have something to tell you later today.

0 Emrys Maier over 9 years ago in reply to AWG

TI__Guru* 96591 points

Andy,

We tested the LVC1G14 (which is the same as the LVC2G14 except that it has only one channel), and it seems that leaving Vcc floating will turn off the output.

This scope shot shows normal operation (Triangular in on Ch 1, Square wave out on Ch 2):

The next one shows the same test with Vcc floating:

0 AWG over 9 years ago in reply to Emrys Maier

Prodigy 170 points

Good morning Emrys,

The answer is enough for me.

For me it looks as if the device is not damaged when the Vcc Pin is left Floating, so you can close this case.

Many thanks for your efforts.

Andy

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74lvc2g14