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ADUM341E0BRWZ-RL - Issue similar to loading effect

Category: Hardware
Product Number: ADUM341E0BRWZ-RL


Currently we are facing some other issues.

I will try to explain my circuit in brief,

we have one processor card and 4 Analog Cards which are connected in a Backplane. In each analog card, we have 2 ADC's communicating through SPI. Also with in each analog card, we have one digital isolator (ADUM341E0BRWZ-RL) after the ADC's. the voltage is level shifted from 5V-3.3V by the Digital isolator.. After this digital isolator, the SPI lines are travelling through the backplane which is in 3.3V logic and reaches processor card. In the processor card, we have one level translator which translates the logic from 3.3V to 1.8V. Then it is going directly to the processor. This is the Flow of circuit.
The current Scenario is
If we are connecting 1 analog card, everything is working fine and we are getting proper reading. the MISO voltage level is also stable.
if we are connecting 2 Analog cards, The ADC configuration and reading also we are getting. But the voltage level of MISO after the digital isolator( In the Analog Card itself) drops to 2V.
if we are connecting 3 Analog cards, its somehow working, but cant say a consistency. Here also the MISO voltage level is reduced below 2V( Around 1.8-1.9V).
If we are connecting 4 Analog cards, it wont work, we didn't get reading from any ADC's even configuration setting also not possible. The voltage level of MISO will drop below 1V.
We checked all the voltage rails during the SPI communication, We didn't identified any Voltage dip in the power rails. Also the ADC side MISO voltage level is also stable which is 5V. Only after the digital isolator we are facing the dip in the level.
All the other line except MISO looks ok.
May i know the reason for the voltage level decrease in the MISO line after digital isolator. Could you please help us to root cause the issue

  • Are the MISO outputs from each analog card tied together on the backplane? If so are the VE1 enable inputs of the ADuM341 being used to high-z the outputs which are not communicating? From the description it sounds like the MISO outputs are shorted together and the outputs are all enabled at the same time.