LP2985: Thermal information

Hi Pao,

Tc is the measured case temperature at the top of the IC. You will need to measure this. The following Application Report goes into more detail about how to measure and use this measurement: www.ti.com/.../spra953c.pdf

Tj is calculated using a measurement, power dissipation for the application, and a specification from the thermal information table. The most common used is θja:

For example, if the ambient temperature is 25 C, θja is 206 C/W, and Pd for the application is 0.25W, we can calculate Tj as follows:

Tj = θja * Pd + Ta
Tj = 206 C/W * 0.25 W + 25 C
Tj = 76.5 C

θjc (top) = 76.1 C/W

Pd is determined by your application. Pd = (Vin - Vout) * Iout

Very Respectfully,
Ryan