# ADum5211 Isolator Input Current Question

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 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?

Parents
• Hello Kornaktech

Thank you for finding that.  You are perfectly correct and your calculation is spot on. It is a typo, 30mA is Iiso max.  The number should be the same as in the ADuM5010 data sheet, 104mA typical.

I will put a correction in for the data sheet.

Best Regards,

MSCantrell

• Hello Kornaktech

Thank you for finding that.  You are perfectly correct and your calculation is spot on. It is a typo, 30mA is Iiso max.  The number should be the same as in the ADuM5010 data sheet, 104mA typical.