ISOW7841: Over-voltage protection
Part Number: ISOW7841
We have build the board with several ISOW7841 + overvoltage protection circuit as per SLLA440 and revised resistor values from our previous correspondence. Unfortunately, none of ISOW7841s turns on - it seems that PFET is preventing it (when PFET is removed, the output voltage is fine).
I have attached my schematic - could you please have a look and advise!?
Thanks,Goran320879-B 11_RS422-3 Interface-Isolated.pdf
Hi Goran,I am Manuel Chavez, a colleague of Koteshwar's. Gate capacitance of PMV30XPEA might be too high for TLV3012 to drive, so the P-FET may be continuously shorting +3V3-ISO3 to 0V-ISO3. Can you attempt to use DMP3056L instead?Thank you,Manuel Chavez
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In reply to Manuel Chavez:
Thank you very much for your prompt reply - I'll try DMP3056L (it will take few days to get it in).
My only concern is that DMP3056L has much higher gate-source threshold voltage than PMV30XPEA, so UVTP might need to be increased as well - I'll let you know the outcome.
In reply to Gorbal:
Hi Goran,No problem! Thank you for anticipating the request and placing an order for DMP3056L.Before modifying UVTP levels, can you re-attempt tests of PMV30XPEA with the drain and source pins switched? I had not realized earlier, but this component might be connected incorrectly.I look forward to your response.Best,Manuel Chavez
Hi Goran,Hopefully all is well. Please let us know if switching the drain and source pins of the P-FET as mentioned above allowed the ISOW7841s in this circuit to power on.Have a great weekend!Manuel Chavez
Sure will do - the reason I have been quiet was that I had some urgent things to do on other projects - I hope I'll get back to this one mid-week and will let you know how it goes. Having said that (and looking again at the AN and my drawings), I am quite sure that the swapping drain and source pins will solve it - sometimes the most obvious errors are easily missed :-(.
I'll be in touch as soon as I get some results!
Hi Goran,No worries! I apologize for initially missing this.. I'm glad we've found a possible solution and look forward to hearing back from you :)Respectfully,Manuel Chavez
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