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Hello

We would like to know that a current from Viso of ADuM6211 meets VDD2 of ADuM6211 and VCC of ADM3101E.

We will use thme at below condition.

Condition

ADuM6211: ( 3.3V supply at primary and sencondary)

We think below from description of datasheet.

Is it correct ?

power supply current : 2.3 mA  Max

power supply current : 7mA Max

So needed current is 2.3+7=9.3mA

Current from Viso of ADuM6211 is 20mA max at VDDp 77mA.

But, current needed by load capacitance is described in ADM3101E datahseet rev.C P.6 Figure 9.

So if load capacitance is over about  800pF  ( we think about 11mA at 800pF from Figure9)

the current from Viso can not meet VDD2 of ADuM6211 and VCC of ADM3101E.

Generally, 20feet of cable length is 1000pF.

So the cable lenght which we can use 16 feet max ( 20feet * 800pf/1000pf = 16 feet).

If there is any wrong with our understanding, please let me know it.

Regards,

Teruamsa

• Hi Teruamsa,

For the application setup described, i think that the  current from Viso of ADuM6211 meets the requirements of VDD2 of ADuM6211 and VCC of ADM3101E.

power supply current : 2.3 mA  Max.

power supply current : ~12mA at 1000 pF load.

2.3mA + 12mA = 14.3mA total.

Current from Viso of ADuM6211 is 20mA max at VDDp 77mA.
So the current from Viso of ADuM6211 meets the requirements of VDD2 of ADuM6211 and VCC of ADM3101E.

Regards,

Richard

• Hello RAnslow,

Datasheet P.3 says that power supply current is 7mA MAX at 3Kohm load resistance.

Datasheet P.6 FIgure 9 says poewr supply current for load capacitance.

I tought that there is a current for load resistance of input resistance of receiver and a current for load capacitance of a cable.

So,  in the condition of using cable and receiver,

I tought that needed current is total of 2.3mA (ADuM6211) and 7mA (ADM3101E) and 12mA (1000pF) =21.3mA .

Is above my understanding wrong ?

If so, please let me know your advice how to use for  Figure 9 (load capacitance) and P.3 power supply current ( load resistance)   in estimating total current .

Best Regards,

Terumasa

• Hi Terumasa,

Yes, you are correct.

The receiver input resistance is specified to be between 3 kΩ and 7kΩ, 5 kΩ is used as a typical, and 3 kΩ is the worst case from a power point of view.

So, the 7mA in the data sheet is a worst case scenario.

Under typical operation for 3 kΩ the current could be 5 mA or less, allowing you to come in less than 20mA for the overall application.

If you can increase the power supply voltage of the ADuM6211 to one of these setups;
5 V PRIMARY INPUT SUPPLY/5 V SECONDARY ISOLATED SUPPLY
5 V PRIMARY INPUT SUPPLY/3.3 V SECONDARY ISOLATED SUPPLY
Then you can provide up to 30mA from Viso of ADuM6211.

This might be an alternative for this customer ?

Regards,

Richard

• Hello RAnslow,