AM26C31 Line Driver

Elvis,

I have not seen this type of damage on AM26C31 before. It seems to center around pin 4 which is surprising.
In what application is this device being used.
Is it always U8 that goes bad or sometime U9?

Hi Ron,

The AM26C31 has being used by pulse output control application, the and output pins connected to motor control servo(CW/CCW mode). 9 in 10 cases (88%) happened to U8, just one on U9.

Thanks and regards,

Elvis

Elvis,

The damaged is electrical over stress, however the cause is uncertain.
Could there be a large difference between the ground on the AM26C31 and the ground of the board that receives the signal?

Hi Ronald,

The ground between the AM26C31 and the board, which should not a large difference as using the common ground.

How big voltage and current could be to cause the damaged like that ( as the photo above ), or any suggested protection methods to avoid the issue.

Many thanks,

Elvis

Elvis,

I can try to damage some part this week. However, I do not expect to see the same level of damage.

Hi Ron,

Many thanks for your help, we're looking forward to receive further information that can feedback to end user.

Regards,

Elvis

Elvis,

To help me break it like customer, can I get a schematic?
Are any pins connected directly to VCC or GND? (other than pins of that name)

Hi Ron,

Please see the schematic of the AM26C31 part below.

The user application of this case, output pin connected jumpers of the line driver will all keep the pin 1 and pin 2 short. 

Regards,

Elvis

Elvis,

AM26C31 I have tried normal over stresses such as over/under shoots with absolute max VCC. No problems observed so far.

I will get more aggressive in the coming week.

Hi Ron,

Understand. If any more detail information is required, please let me know.

Thanks,

Elvis

Elvis,

I was able to damage a device by injecting hundreds mili-amperes of negative current into pins 3 or 5.
Pin 4 current also became high during the stress. My part did not burn even though ICC became 500mA after the stress
I was going to check a new device without put VCC on pin 4 and in the middle of testing my lab equipment broke so it's time to stop for the day.

Elvis,

I spent some time on this in the last couple weeks and I could break a part by over-stressing the inputs but there was no sustained high ICC current that would be needed to burn the device. If the RS485 port can not cause this burning unless there is power on the bus that is some external power that is not RS485 compliant.

Do you know which pins on the burnt device that are shorted or open. I assume the VCC to ground is shorted for example

Hi Ronald,

Thank you for your help of the examinations and experiments.

I can report to our end user that there are no device issue, and which has been ensured by a period of testing. Besides, I can't sure which pins that are shorted or open of the burnt device, but some external power caused the issue could be the root in this case. Therefore, a protection circuit will be highly considered to the line driver, yet which must avoid to cause any side effect in the signal transmission.

Are there any suggestions that can be referenced to the protection circuit of AM26C31 line driver IC.

Many thanks,

Elvis

Elvis,

For better ESD and surge protection, try tpd4e1u06