SN74ALVC125: SN74ALVC125 Buffer IC input pin failure

chandran j

Prodigy 40 points

Part Number: SN74ALVC125
Other Parts Discussed in Thread: STRIKE

We are using the SN74ALVC125 for VFD PWM buffer IC control

In the process observed one channel of Buffer IC got failed while switching. (Ref:U6 2nd Pin)

PWM_BUFF_BLK we made common Pull-up for 2 SN74ALVC125 IC (output enable pin ) is there any issue due to common pull-up

PCB Track distance between DSP to SN74ALVC125 almost 60mm

continuously we found same issue in two boards

Please refer the image

over 2 years ago

0 Emrys Maier over 2 years ago

TI__Guru* 96661 points

Hello,

There's no problem with using a 10k resistor to pull up multiple inputs.

What kind of failure are you seeing on the input? Also, can you share a scope shot of normal operation for that channel (input and output)?

0 chandran j over 2 years ago in reply to Emrys Maier

Prodigy 40 points

Hello Emrys Maier,

Thank you for your reply

In faulty condition, input to one channel of buffer IC is switching between 0 to 0.5V, instead of 0 to 3.3V ( probably, pin is getting loaded somehow).

Output is steady state condition.( not at all switching)

Right now we don't have captured waveform with us. If really required we can have it.

0 Emrys Maier over 2 years ago in reply to chandran j

TI__Guru* 96661 points

It sounds like the input has been damaged. The most common method for this is an ESD strike.

0 chandran j over 2 years ago in reply to Emrys Maier

Prodigy 40 points

Device(SN74ALVC125) it self available ESD protection,

any thing we to take care in our system, (Can you Suggest any design improvement required in our system.)

0 Emrys Maier over 2 years ago in reply to chandran j

TI__Guru* 96661 points

I can't see your entire system - only a very limited view of my device - so I can't really provide input to improving the system. I'm just giving you the most common reason for a failure like this. I haven't even seen the voltage inputs to my device (oscope shot).

The ESD protection for this device is not sufficient for a system-level ESD application. If the inputs are exposed to possible ESD strikes, you will need additional ESD protection.

We have an app note that talks about this in detail: https://www.ti.com/lit/slyt492

Page 1 has a section "System-level versus device-level ESD protection" that explains this very well.

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SN74ALVC125: SN74ALVC125 Buffer IC input pin failure