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ISO1050: ISO1050 power ramp up question

Peter Chen(ICP_FAE)
Intellectual 2480 points
Part Number: ISO1050

Is there any power ramp up sequence required in ISO1050? It looks that VCC2(Transceiver-side supply voltage)ramp earlier than VCC1(Digital-side supply voltage). the CAN output does not output (CANH and CANL) in short period. but if zoom out the observe time, the ISO1050 output correctly.

Is that due to ISO1050 device need the time to resume from protected state to normal operation? 

ISO1050 output question.docx

Yellow : VCC1_3.3V
Blue : TXD(ISO1050 input)
Purple : VCC2_5V
Green : CNA BUS(CANH-CANL; ISO1050 output)
 
Longer the time, the CAN looks working well.
 
  • 0
    TI__Intellectual 2900 points
    Hi Peter,

    The device is expected to work under such a condition. Could you please help with a few more details to help us debug this?

    According to the captures you have shared , it looks as if the supply has some noise (yellow line is switching a lot in the oscilloscope capture). Since this switching is very faint and present on multiple lines, it could be the oscilloscope is accidentally capturing some external noise, please check whether this is actual noise seen by the device on the supply lines.

    1) Was this behavior observed on multiple devices or just one IC?
    2) Would it be possible to share the schematic for the ISO part?
    3) Could you please ensure that there are proper Decoupling capacitors placed very close to the IC pins VCC1 and VCC2?
    4) For the captures you have shared in your previous post, where are you probing with the oscilloscope? Are the measurements being done at the IC pin?

    Thanks you for helping us out with theses details, it should help us move ahead with this debug.

    Regards,
    Anand Reghunathan
  • 0 in reply to Anand Reghunathan
    TI__Intellectual 2480 points

    more detail information is going though by mail.