SN65HVD485E: RO output is abnormal

Sara Jia

Part Number: SN65HVD485E
Other Parts Discussed in Thread: SN75176B,

Hi Sir,

Under certain environment, the chip enters an abnormal state, the RO output high level changes to about 1V, the chip becomes hot, and the fault mode can only be launched after the chip is recharged. If the chip is in the above state for a long time, the chip will be damaged. But SN75176B has no such problem.

So why has this problem in SN65HVD485E? How to avoid it? Pls give us some recommendation.

Thanks.

Sara

over 6 years ago

0 Miguel Robertson over 6 years ago

TI__Guru 62920 points

Sara,

I've never encountered this issue, so I hope you can help me to better understand it. What conditions seem to cause this behavior to occur?

Thanks,

Max

0 Sara Jia over 6 years ago in reply to Miguel Robertson

Expert 2975 points

Hi Max,

Thanks for your reply.Use USB to 485 converter to monitor data, repeatedly plug and pull the USB port of this converter to reproduce the problem.

Sara jia

0 Miguel Robertson over 6 years ago in reply to Sara Jia

TI__Guru 62920 points

Hi Sara,

It sounds like a latch-up issue to me, although I'm not aware of any latch-up sensitivities with this component. Would it be possible to probe the inputs to the transceiver when the cable is plugged and unplugged to see how this might be stressing the device? (Sometimes these kinds of "hot plug" events can result in voltage spikes at the IC pins that route to the connector.) If the cable is used to deliver power, it may be related to a power ramp profile as well (for example, overshoot on VCC at turn-on). In that case it would be good to also probe the VCC line.

Max

0 Miguel Robertson over 6 years ago in reply to Miguel Robertson

TI__Guru 62920 points

Hi Sara,

Have you had a chance to look into this any further? Or, have you been able to resolve the issue?

Max

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SN65HVD485E: RO output is abnormal