ISO7342CEVM: ISO734X DOES NOT WORK

Bobby Lam95

Part Number: ISO7342CEVM
Other Parts Discussed in Thread: ISO7741EVM

i bought this ISO73xx Triple/Quad Digital Isolator Evaluation Module a couple months ago. I just hooked up today and find it does not output the signal that is fed in the input. Both of the 5V supply rails are good and isolated, The signal can be seen at the input pins, but not the output pins. I replace the IC and still not working. The enable line does not do anything at high or low. Any suggestion? Thank you

Bobby.

over 5 years ago

0 Dan Kisling over 5 years ago

TI__Expert 6195 points

Hi Bobby,

I'm not sure why you are not able to see the outputs. Would you be able to provide some additional details on the experiment you have run.

What was the transmit signal you used?

Can you provide a picture EVM so I can see how you have the jumpers configured? I have attempted to give a crude markup of the EVM showing where the jumpers should be placed.

Best regards,

Dan

0 Bobby Lam95 over 5 years ago in reply to Dan Kisling

Intellectual 320 points

Hi Dan,
Thanks for the response. The circuit is very intuitive and I don't see why it does not work. I fed in a signal 3.3 Vpp square wave from a PIC micro at 20 KHz. When I powered up the supplies, the signal drop to 1 Vpp. I got a signal generator and feed the same 3.3Vpp square wave and it comes out fine. How much current does this part sink?
Bobby.

0 Bobby Lam95 over 5 years ago in reply to Bobby Lam95

Intellectual 320 points

Hi Dan,
I took the 50 ohm termination resistor off the input and the signal comes out on the output. This is good, but I want to understand the purpose of the input termination resistor. Can you explain? or should put some high value of resistor rather than none at all? thank
Bobby.

0 Dan Kisling over 5 years ago in reply to Bobby Lam95

TI__Expert 6195 points

Hi Bobby,
The input termination resistor is not necessary. On our newer EVMs (ISO7741EVM and ISO7842EVM) we have not included it. For most applications it is fine to just connect the digital isolator channels to the microcontroller directly. I'm sorry for any confusion.
Did you have any other questions?
Best regards,
Dan

0 Bobby Lam95 over 5 years ago in reply to Dan Kisling

Intellectual 320 points

That's good to know. I am good now. Thank you very much. I close out this issue.
Bobby.

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ISO7342CEVM: ISO734X DOES NOT WORK