# Power Dissipation vs Die Temp

A calculator for estimating junction temperature from power dissipation and packaging/heatsink characteristics.

### Instructions

This calculator computes die power dissipation and temperature for a linearly regulated output from quantities specified under "Parameters". It also computes power dissipated in an external load.

The model is of a linear push-pull output driving an external resistive load. Two common examples would be a digital bipolar output or a Class A amplifier. The voltage across the resistor, VOUT-VGND determines the current, IL, supplied by the output, which requires the internal driver dissipate IL * (V+-VOUT) or IL * (VOUT-V-) to supply the current linearly. Which rail supplies the current depends on whether the load current is positive or negative.

Total on-chip power, PTOTAL, is the sum of the power dissipated driving the load, plus the quiescent power, IQ * (V+-V-). The on-chip rise is equal to TA + thetaJA*PTOTAL. ThetaJA = ThetaJP (junction-to-package) + ThetaPA (package-to-ambient).

To use this calculator, simply enter the appropriate quantities in the parameter fields and then click "Calculate" or tab from field to field.

### Related Information

#### Mini Tutorials

• MT-093: Thermal Design Basics (pdf)