# Power Dissipation Calculations ?

#### uhdam

Joined Jan 24, 2013
23
In my circuit, I am using the ADuM226N Digital Isolator and also using the TJA1052IT/5 CAN Transceiver. I want to calculate the Power Dissipation over Digital Isolator and CAN Transceiver. Any one help me with the formula and how to calculate the power dissipation on both chips ?

#### WBahn

Joined Mar 31, 2012
26,398
In my circuit, I am using the ADuM226N Digital Isolator and also using the TJA1052IT/5 CAN Transceiver. I want to calculate the Power Dissipation over Digital Isolator and CAN Transceiver. Any one help me with the formula and how to calculate the power dissipation on both chips ?
Power calculations for an IC can only be done using the data in the IC's datasheet. To see that this is true, picture two ICs that are identical except that one has a resistor between power and ground. That will mean that the two ICs dissipate different amounts of power and there is no way to know how much unless you use the data in the datasheet. So look up the datasheets for those two ICs and go from there.

#### uhdam

Joined Jan 24, 2013
23
Power calculations for an IC can only be done using the data in the IC's datasheet. To see that this is true, picture two ICs that are identical except that one has a resistor between power and ground. That will mean that the two ICs dissipate different amounts of power and there is no way to know how much unless you use the data in the datasheet. So look up the datasheets for those two ICs and go from there.
The two IC's are used for different cases that is different story. In this stage consider one IC only, in the datasheet they are not given any formula to calculate the power dissipation. Usually, when calculating the power dissipation for IC's they will give the formula and procedure to do how to calculate. But, in the datasheets of the both IC's they are not given. So that is why I am asking how to proceed.

#### bertus

Joined Apr 5, 2008
21,534

#### RichardO

Joined May 4, 2013
2,271
The two IC's are used for different cases that is different story. In this stage consider one IC only, in the datasheet they are not given any formula to calculate the power dissipation. Usually, when calculating the power dissipation for IC's they will give the formula and procedure to do how to calculate. But, in the datasheets of the both IC's they are not given. So that is why I am asking how to proceed.
They do give power supply current draw specifications. Start from there. Then you add whatever power is used by any loads that you connect to the IC.
If you need dynamic power dissipation then you will have to use spec's from the data sheet and add that to get total power used.

If power usage is not continuous, such as when a device is sometimes in standby mode, then you have to estimate what percentage of the time the power is used and correct for that.

edit: bertus shows where to look in the data sheet.

#### uhdam

Joined Jan 24, 2013
23

#### uhdam

Joined Jan 24, 2013
23
They do give power supply current draw specifications. Start from there. Then you add whatever power is used by any loads that you connect to the IC.
If you need dynamic power dissipation then you will have to use spec's from the data sheet and add that to get total power used.

If power usage is not continuous, such as when a device is sometimes in standby mode, then you have to estimate what percentage of the time the power is used and correct for that.

edit: bertus shows where to look in the data sheet.
Please can you explain which formula I suppose to use and how to calculate. If you don't mine can you calculate with an example.

#### RichardO

Joined May 4, 2013
2,271
Please can you explain which formula I suppose to use and how to calculate. If you don't mine can you calculate with an example.
Power is volts times amps time the time the circuit is on over the time the circuit ios off: W= V*A*T_on/T_off.