AD1582: Requirements for heat sinking

Document created by analog-archivist Employee on Feb 23, 2016
Version 1Show Document
  • View in full screen mode

i want to know if i will need a heat sink fro this device (Vin=3.3V and
Iout=100uA). Therefore, i need to know what are the Tj, Tjunction-ambient and
Tjunction-case.
can you send me those parameters?

 

The thetaJA for the sot 23 package used by the AD1582 is 300degC/W. A max
junction temperature of 125degC is a good assumption for this device.

Total power consumption is 3.3V x 65uA + (3.3V – 2.5V) x 100uA = 214uW + 80uW =
280uW
Expected junction temperature rise above ambient = 300degC/W x 280uW = 0.08degC

As you can see the power dissipation in the AD1582 even when sourcing 100uA is
so low that the rise in junction temperature will be less than 1degC. A heat
sink should not be required in such conditions.

As an aside, note that the thetaJA we quote on the datasheet (usually found in
the absolute maximum ratings sections) uses a “SEMI standard board” under still
air conditions according to SEMI standard G38-87. This assumes a large copper
area ground plane approx 2inch x 2 inch which acts as a heat sink. The area of
adjacent ground plan and the width of PCB track which used to connect the
component pad can all affect the thermal resistance of the package.

Attachments

    Outcomes