SN65HVD3088E: SN65HVD3088E weird waveform

Frank Xiao

Genius 12055 points

Part Number: SN65HVD3088E

Hi team,

My customer is using the SN65HVD3088 now, when they test our 485 and other competitor's 485, they find some weird waveforms.The waveforms are below. Could you please help explain it?(The left is receive and the right is transmit)

other competitor 485

SN65HVD3088 waveform( the amplitude is small, and the waveform has sunken)

The schematic is below.

Although it will not influence the connection, we want to check the why our device waveform is weird. The customer has concern to use it.

Thanks.

Frank

over 7 years ago

0 Hao L over 7 years ago

TI__Mastermind 25705 points

Frank,
Unfortunately I've never seen this before. Do you know the loading of the bus, like the other end of the bus? Is DF1 the cable model? How long is the cable? Is the waveform differential signal (VA-VB)? Do you know the voltage level of the dipping and its period?
Regards,

0 Frank Xiao over 7 years ago in reply to Hao L

TI__Genius 12055 points

Hi Hao,

Only one load, DF1 is common mode choke, the cable 0.5m, it's VA-VB waveform. The baud rate is 2.5M. Thanks.

BR
Frank

0 Hao L over 7 years ago in reply to Frank Xiao

TI__Mastermind 25705 points

Frank,
Can you test without the choke? Can you also test with clock signal with different frequncy? If it is still no clue, can you probe VA and VB separately? Thanks,

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SN65HVD3088E: SN65HVD3088E weird waveform