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ADum5211 Isolator Input Current Question

Question asked by kornaktech on Apr 30, 2013
Latest reply on May 13, 2013 by MSCantrell

I am trying to determine much current the ADuM5211 will draw if it is operating at 1Mbps and also powering an isolated LED at 12mA.  Therefore, the isolator power section is supplying about 18mA of isolated current (Idd1=2.7mA and Idd2=2.9mA max at 1Mbps).

 

The Rev 0 ADuM5210/ADuM5211/ADuM5212 datasheet seems inconsistent.

 

The maximum current that the device can supply is 30mA.

Output Supply   Iiso (MAX) = 30mA

 

The power supply input current is listed as...

IDDP, No Viso Load   IDDP (Q)   = 6.8mA to 12mA

IDDP, Full Viso Load IDDP (MAX) = 30mA

 

That second number seems wrong since the efficiency is listed as...

Efficiency at Iiso (MAX)        = 29% (Iiso = 27mA)

 

Wouldn't the input current draw at full output be...

IDDP (MAX) = 30mA / 29% = 103mA (at Iiso=30mA)

 

Would IDDP = 18mA / 29% = 62mA (at Iiso=18mA) be a good input current estimate? Or would the efficiency be worse around half load?

 

Thanks for your help.

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