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LDO Power Dissipation Calculator
This calculator estimates power dissipation, efficiency, voltage drop, and junction temperature rise for a linear regulator or LDO. It is useful for checking regulator heat, package thermal limits, dropout margin, and safe operating conditions in power supply design.
Input Parameters
Results
LDO power loss rises directly with voltage drop and load current. A small package may overheat even when the output current is within the electrical rating.
Equations Used
LDO Power Dissipation:
PD = (Vin - Vout) × Iout + Vin × Iq
Efficiency:
Efficiency = (Vout × Iout) / (Vin × (Iout + Iq)) × 100%
Temperature Rise:
ΔT = PD × θJA
Junction Temperature:
TJ = TA + ΔT
Where:
Vin = input voltage
Vout = output voltage
Iout = load current
Iq = quiescent current
θJA = junction-to-ambient thermal resistance
TA = ambient temperature
Frequently Asked Questions (FAQ)
Q1: What does this LDO power dissipation calculator do?
It estimates heat generated by an LDO or linear regulator from input voltage, output voltage, load current, quiescent current, and thermal resistance.
Q2: Why does an LDO get hot?
An LDO burns the voltage difference between input and output as heat. Higher voltage drop or higher load current increases power dissipation.
Q3: What is θJA?
θJA is junction-to-ambient thermal resistance. It estimates how many degrees Celsius the IC junction rises for each watt of dissipated power.
Q4: How can I reduce LDO power dissipation?
Reduce input voltage, reduce load current, use a regulator package with better thermal performance, add copper area, or use a buck converter before the LDO.
Q5: Is efficiency always low for LDOs?
LDO efficiency is roughly limited by Vout / Vin. It can be high when Vin is close to Vout, but poor when the voltage drop is large.
Q6: Should I include quiescent current?
Yes, especially for low-power or battery designs. In high-current designs, load-current loss usually dominates.
