SN65HVD3082E baud rate issue

Pradhan Rivankar

Other Parts Discussed in Thread: SN65HVD3082E

1332-3PProtel Schematic.pdfDear Sir / madam

We are using a PCB for communication using TI device SN65HVD3082E.

We have studied the datasheet of IC SN65HVD3082E, this device is optimized for signaling rates up to 200 Kbps, but in our application signaling baud rate is up to 115.200 Kbps still it is not working, so please guide whether we are wrong in our circuit diagram. Attached is the schematic.

Thanks and regards

Pradhan

over 9 years ago

0 Miguel Robertson over 9 years ago

TI__Guru 62920 points

Hi Pradhan,

It would be good to try to view the waveforms at the D, DE, A, B, and R pins on an oscilloscope to get a better understanding of what exactly is going wrong. Just looking at the schematic, my main concern is the response time of the PC817 opto-coupler. At 115.7 kbps baud rate, each bit period is about 8.7 us. The rise/fall times of the PC817 look to be > 40 us when a 4.7 kOhm load resistance is used. This would be too slow for the data to properly cross through the opto-coupler devices.

Regards,
Max

0 Pradhan Rivankar over 9 years ago in reply to Miguel Robertson

Expert 1080 points

Thanks Max for your quick reply.

Can you please advice what should be the load resistance value and also any suitable optocoupler that will support the 115200 baud rate?

Awaiting for your kind response.

Thanks in advance
Pradhan

0 Miguel Robertson over 9 years ago in reply to Pradhan Rivankar

TI__Guru 62920 points

Pradhan,

It looks like even with the minimum specified load resistance of 100 Ohms, the response time will be too slow. I'm not sure about what optocouplers may exist that could handle this data rate, unfortunately. If you are not able to find one that is fast enough, you may instead want to consider a digital isolator device; these are designed to support high baud rate communication. You can find more information here: www.ti.com/.../digital-isolators-overview.page. You can also get more detailed guidance from their e2e forum, found here: e2e.ti.com/.../1013.

Regards,
Max

0 Pradhan Rivankar over 9 years ago in reply to Miguel Robertson

Expert 1080 points

Thanks Max

Really Appreciate your quick response.

Thanks a lot
Pradhan

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SN65HVD3082E baud rate issue