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Power Supply's Ripple Disturbs the Decoder of iCoupler?

Question asked by starraytheon on May 23, 2013
Latest reply on May 23, 2013 by starraytheon

Hi Experts,

 

I am learning the iCoupler basic theory and application now.

I have been confused by   " DC CORRECTNESS AND MAGNETIC FIELD IMMUNITY---Positive and negative logic transitions at the isolator input cause narrow (~1 ns) pulses to be sent via the transformer to the decoder. The decoder is bistable and is, therefore, either set or reset by the pulses, indicating input logic transitions.    In the absence of logic transitions at the input for more than ~1 μs, a periodic set of refresh pulses indicative of the correct input state is sent to ensure dc correctness at the output. If the decoder receives no internal pulses for more than approximately 5 μs, the input side is assumed to be without power or nonfunctional; in which case, the isolator output is forced to a default state (seeTable 20 and Table 21) by the watchdog timer circuit."  in page 13 of ADuM2210/2211' spec.

 

Question: If the power supply(never mind Vdd1 or Vdd2) has been coupled the ripple that can generate the high frequency inteference at the 1G Hz (in frequency domain analysis).

when the energy is enough to disturb the narrow pulses, the inteference can disturb the logic circuits in the decoder through the resistance coupling. such as nmos plus pmos pair (inverter)?  I think that the encoder and decoder have some basic logic units internal.

So, the bad power supply can make the icoupler malfunction.

Is it correct? Above is my personal opinion. Thanks for your help!

 

Yours Sincerely,

Tom

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