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ISO1050: ISO1050 LOW TEMPERATURE START-UP PROBLEM

cyan zhou
Expert 1500 points

Part Number: ISO1050
Other Parts Discussed in Thread: ISO1042

Hi Sir,

ISO1050DUBR, I meet a problem: 

Test condition: -30℃;  DSP: F28034PNT; CAN:ISO1050DUBR

Because of our design defect, the Vcc2 of ISO1050 will drop from 5V to 0.6V, and ISO1050 stop working.  During the Voltage of  Vcc2 rises from 0.58V to 5V,  the ISO1050 works delayed, delay time is about 17.7 seconds, That's not what we want.

below is the wave:  ch1: 5V  for ISO1050 Vcc2;    ch2: TX （connect DSP28034）;  ch3: RX （connect DSP28034）; ch4 CANH/CANL(differential)

Besides, system standby,  when I powered Vcc2 by a external power supply from 0V~5V; that will not be happened; below is the wave:

That's my doubt, only in below -10C, only rise Vcc2 from 0.6V to 5V, the device iso1050 will be work delayed several seconds.

Please help to check.

Thanks and Regaids

Cyan Zhou

  • 0
    TI__Expert 6195 points

    Hi Cyan Zhou,

    I'm sorry to hear you are having issues with the ISO1050. You are correct that this delayed start up is due to low temperature and brownout voltage on Vcc2. More information about this issue can be found on this E2E thread.

    The best solution would be if you could upgrade to the ISO1042. I've tested this isolated CAN transceiver under these conditions and I'm confident it does not have this startup issue. Unfortunately, this device is not pin to pin compatible with the ISO1050 so some layout rework would have to be done. The ISO1042 comes in an 8-pin DWV and 16-pin DW package.

    Another solution is to add a bleed resistor to Vcc2. Assuming that the device is starting up at 0.58V due to the caps not discharging down to zero - a bleed resistor will allow those caps to discharge quickly. If we can get Vcc2 to discharge below 0.3V before starting back up you should not see the startup issue.

    Will either of these solutions work for you?

    Best regards,

    Dan

  • 0 in reply to Dan Kisling
    Expert 1500 points
    Hi Sir，
    Thanks for your quick response.
    We had solved the drop down Voltage of Vcc2, So this won't be happened on ISO1050;
    seems ISO1042 is better than iso1050, we will take a look on it.
  • 0 in reply to cyan zhou
    TI__Expert 6195 points
    Hi Cyan Zhou,
    Yes the ISO1042 is a newer isolated CAN transceiver. It supports CAN FD datarates, has higher bus fault protection, and also a higher isolation rating. If you have any questions about the device please feel free to ask - either in this thread or a new one.
    Best regards,
    Dan