IDD and Power Dissipation

[kudjung]

Can anyone help me here?

I'm trying to specify a current requirement for one of the DAC. It has following spec. Should I use Power Dissipation or Idd to calculate the current requirement?
Another thing is seem like it would draw less power the circuit from 3.3V(from power dissipation), correct?


Thanks in advance for all the help.

 

[KlausST]

Hi,

The following equation should be true: U * I = P

Do you find a (big) difference in that?
If yes, show us your calculations.
If no, then you could use both calculations and get about the same result.

Klaus

 

[kudjung]

Hi,

Attached is the Idd of the same chip. If we directly calculate the current from power dissipation. It seem to be significantly different.

For example,

1.8V, Fs =48 KHz case. Current will be 27 mA to 102 mA which is significantly different from the spec. Idd at 7 mA.


Am i missing something?

Thanks in advance for all the help.

 

[KlausST]

Hi,

Power dissipation is for the complete chip. You ned to know power dissipation to calculate the temperature rise.
Therefore power dissipation is the sum of all U x I.

Vdd and Idd is only one part of the total power dissipation.

Vdd can be 3.3V or 1.8V, the other supply voltages are 3.3V ( at least what I can see from your datasheet snippet).
Therefore the total power dissipation depends on Vdd and the frequency.

Klaus