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ADM2483 with isolated power supply

Question asked by jcrummy on Nov 20, 2014
Latest reply on Nov 25, 2014 by jcrummy

Hello,

 

I'm having an issue with an ADM2483 not doing full 'swings' on the RxD line....

 

I have two ADM2483 side by side, one with an isolated bus power supply of 5V, and one with an non-isolated power supply of 5V. The non-isolated module works just fine, however the RxD line on the isolated module does not swing all the way down to 0V, instead it only goes from 3.3V to about 2V, which isn't enough to trigger a low level on the input to my CPU.

 

The PV line is tied directly to 3.3V (VDD1), and I've checked that the CPU is holding both RE and DE low.

 

The isolated power supply is provided by a RECOM RKE-0505S, data rate is 250,000baud.

 

Does anyone of any ideas to help me out? I'm getting stumped on this one....

 

Thank you,

 

-John

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