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ADuM6401/2 VDD Noise issue

Category: Hardware
Product Number: ADuM6401/2

Hi Team,

We are using ADuM6401 for RS485 (2 no) and ADuM6402 for CAN communication within the same PCB board. Total 3 digital isolator is placed in same PCB with the same VDD (3.3V). Pelase see circuit diagram of RS485 digitla isolator. same circuit configuration used for CAN communication.



* we are observing 41mV Pk-Pk noise at 3.3V VDD supply line(see below attached image). Which is connected to all the three ADuM device and other on Board circuit. As ADC is also connected to the same 3.3V line and geting imapcted. 

Please give your comments to redice the noise in 3.3V VDD line.

Note : We confimed that this noise is because of ADuM device while removing the All the three ADuM Device and observed the noise in 3.3V. 



  • The noise is expected as this is a switching converter operating at ~180MHz with a PWM frequency of ~500kHz. The noise may be decreased by reducing the impedance of the decoupling network on VDD1 and/or adding an additional LC filter between this part and the source voltage. Note that the ADuM640x parts are not designed to operate and are not tested with 3.3V on the input and 5V on the output.