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# TPS62130A-Q1: Calculating the Junction Temperature

Part Number: TPS62130A-Q1
Other Parts Discussed in Thread: TPS62130

We have estimated the power dissipation on the TPS62130A-Q1 mounted on a 10-layer HDI PCB as 0.7W based on measured data.

The thermal resistance parameters mentioned in the datasheet are as below:

In our measurement setup, we are measuring the temperature on the component top and on the PCB right next to the component as shown below:

Q1: Can we calculate the instantaneous Junction Temperature (TJ) based on the formula given on page 8 of this app note https://www.ti.com/lit/an/spra953c/spra953c.pdf ?

Measured Tc (Thermocouple Ttop from the picture) = 116 C

Hence, TJ = 116.6 + 0.7 x 1.1 = 117.37 C

Q2: We worked out the TJ based on Equation 4 in the same document, fully aware of the caveats mentioned in the explanation.

Measured Tc (Thermocouple TC from the picture) = 115.3 C

Hence, TJ = 115.3 + 0.7 x 4.5 = 118.45 C

This number is close to the value obtained using Equation 8, assuming that the point of measurement is really really close to the bottom case of the device.

Are we on the right track here?

• Hi Pramod！

You are on the right track. I suggest you measure the top case temp as it is easy.

Shuai

• Thanks.

Can we use the same concept (measure the top case temperature and use the ΨJT value to calculate TJ) for all components with a plastic top and without a dedicated heat-sink mounted? Here we are assuming a worst case of 100% of the heat getting dissipated through the top and nothing being conducted into the PCB copper through the bottom thermal pad, giving an over-prediction of a few degrees C.

Case in point, PMIC devices such as TPS6593, TPS6594.

• Hi Pramod!

I can just confirm the rightness of TPS62130. For other devices, I suggest to open other ticket on E2E case by case.

Shuai