Part Number: ISO1050
My customer using ISO1050 discover a issue that RX didn't change when TX sent data.
Please see schematic and waveform as below.
Have you seen similar case?
In reply to Zhe Ming Zhuang65:
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In reply to Dan Kisling:
No, because i don't have jumper on TX and RX trace thus i have to cut off trace to verify this.
(By the way, FW will change the activity if the MCU didn't receive RX data that may confuse us)
But i have done the swap process that on another PCBA the TX RX have no error from CAN log.
And later this ISO1050 may put on TI EVM board to double check this issue.
In reply to user4773196:
Yes. We found this issue also can be reproduced by TI EVM.
I have filled document for requiring your TI support
Following waveforms are measured at EVM by another FAE.
This is TI distributor FAE, CK.
I captured the fail waveform on ISO1050EVM.
Please see the figures as below.
You can see the RXD sometimes will not change after TXD transition from high to low.
Fail unit (zoom in):
Normal unit (zoom in):
The testing methodology is referred to ISO1050EVM user guide.
I just use a function generator to stimulate TXD, then measure the waveform of CANH, CANL, and RXD.
By the way, I found that the failure rate will increase if I decrease the data rate.
When TXD running at 1Mbps, this fail phenomenon will disappear.
But if TXD runs under 600Kbps, you can see the failure occured frequently.
In reply to CK Ho:
Thank you for the additional details. I am having trouble replicating the failure on our end. Could you help provide me with more information on how this experiment was conducted?
This is what I just tested in the lab on the EVM:
Vcc1: 5V, Vcc2: 5V
TX (from signal generator): 0-5V 150kHz square wave with 75% duty cycle. Monitored on scope in yellow.
CANH / CANL: Monitored on scope in green / purple. Not connected to any other nodes on network.
RX: Monitored on scope in pink.Not connected to anything else.
This is what I saw on the scope. I tried to match your scopeshot.
I then setup the trigger to only trigger when TX was LOW and RX was HIGH for greater than 500ns. This should then trigger whenever RX fails to follow TX. This was run for several minutes, but the scope did not trigger. So I was unable to find an instance where the ISO1050 created a bit error.
Yes, only the suspect IC has this fail phenomenon. And the suspect IC is on my hand now.
There is no bit error If I measure the normal one. The waveform is the same as yours. You can see the figure I posted before.
All of your setting is the same as mine, only one is different, I set VCC1=3.3V and TXD=0-3.3V. But I think it doesn't matter.
Thank you very much.
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