Voltage Regulator Temperature Calculator

This tool calculates the junction temperature of a LDO regulator


	

		

Formula

TJ = TA + (RθJA × PD )

where

  • TA is the ambient temperature
  • RθJA is the Junction-to-ambient thermal resistance
  • PD is the power dissipation

PD = (VIN – VOUT) * IOUT + VIN * IQ

The power dissipation is calculated using the following quantities:

  • Input Voltage VIN
  • Output Voltage VOUT
  • Output Current IOUT
  • Quiescent (or Ground) Current IQ

Background

The larger the voltage difference between the input and output, the greater the power dissipation. The temperature is directly proportional to both the Junction-to-ambient thermal resistance and the power dissipation.

Example Calculation

For an input voltage of 5V and regulated output 3.3V, with the output current of 150 mA, Junction-to-ambient thermal resistance of 205 °C/W, the power dissipation is 256 mW and the junction temperature is 77.5 °C.

Related Calculators