ISO7742TB-Q1: ISO7742 not driving Isolating transformer

digilog

Part Number: ISO7742TB-Q1
Other Parts Discussed in Thread: ISO7742

I have designed a PCB using the ISO7742TBDWRQ1 and the Wurth 760390015 transformer and have followed the data sheet and application notes on the design but the ISO7742 pin 1 and pin 2 do not oscillate and are fixed at 3.3v.

The power supply to the device is 3.3V and I have verified this on the board.

I have checked all connections and layout and cannot see any obvious problems. Each of my boards contain 2 of these circuits and I have so far tested 2 boards and non of the ISO7742 devices are operating.

The only thing I can see is that at the moment the INA, INB are floating and measure about 3V but according to the data sheet this should be OK?

DO you have any ideas as to why these are not working?

ISO7742.pdf

5 months ago

+1 Aaditya V. 5 months ago

TI__Mastermind 21565 points

Hello,

Thanks for reaching out.

I understand you are having trouble with getting the ISO7742T-Q1 to function as expected. Can you please double confirm the part number of the device?

It seem that the schematic says ISO7742DWR, which is an entirely different device which has no integrated transformer driver.

Digital Isolator --> ISO7742DWR: https://www.ti.com/product/ISO7742

Digital Isolator with integrated transformer driver --> ISO7742TBQDWRQ1: https://www.ti.com/product/ISO7742TB-Q1

Regards,
Aaditya

+1 digilog 5 months ago

Prodigy 155 points

Yes you are right. I have rechecked the part number on the device and it is the DWR version. I had actually specified the TB-Q1 version in the BOM but the assembly house did not fit the correct part. Thanks for your reply.

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ISO7742TB-Q1: ISO7742 not driving Isolating transformer