Power Management

LDO Loss & Thermal Calculator

Linear Regulators (LDOs) drop voltage by dissipating excess energy as heat. This makes Power Dissipation (PD) and Thermal Management critical design factors.

This calculator determines if your regulator will overheat. It calculates the junction temperature based on the input/output differential, load current, and the package’s thermal resistance (θJA).

Operating Conditions

Input
V
V
mA

Device Limits & Thermal

Specs
V
°C
°C/W
°C

Performance Analysis

Result
Power Dissipation (PD)
— W
Eff: — %
Junction Temp (TJ)
— °C
Enter parameters
LDO

Formulas Explained

Power Dissipation (PD)

PD = (Vin – Vout) × Iload

Heat generated by voltage drop.

Junction Temp (TJ)

TJ = Tamb + (PD × θJA)

Must stay below the Max TJ.

Efficiency (η)

η = (Pout / Pin) × 100

LDOs are inefficient when Vin >> Vout.

Dropout Condition

Vin ≥ Vout + Vdropout

Regulator stops working if Vin dips too low.

How to Use

Check thermal safety in 3 steps.

1

Define Operation

Enter voltages (Vin, Vout) and load current. Don’t forget the Dropout Voltage from your datasheet.

2

Set Limits

Input the Thermal Resistance (θJA) and Max Temp. Use the quick buttons for common packages like TO-220.

3

Analyze Results

If the Junction Temp turns RED, you need a heatsink or a switching regulator.