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LDO Efficiency Equation:
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LDO (Low Dropout) regulator efficiency is the ratio of output power to input power, expressed as a percentage. For LDOs, since the current is approximately the same on input and output, the efficiency can be simplified to the ratio of output voltage to input voltage.
The calculator uses the LDO efficiency equation:
Where:
Explanation: The equation calculates what percentage of the input voltage is being delivered to the output. Higher efficiency means less power is dissipated as heat in the regulator.
Details: Efficiency is crucial for battery-powered applications where power conservation is important. Lower efficiency means more power is wasted as heat, which can also affect thermal design.
Tips: Enter both output and input voltages in volts. Both values must be positive numbers. The output voltage must be less than or equal to the input voltage for an LDO.
Q1: What is a typical LDO efficiency?
A: Efficiency depends on the voltage difference. For example, with 3.3V output from 5V input, efficiency would be 66%. With 3.3V from 3.6V, it would be 91.7%.
Q2: Why is LDO efficiency often lower than switching regulators?
A: LDOs dissipate excess voltage as heat, while switching regulators convert power more efficiently through switching action.
Q3: When should I use an LDO despite its lower efficiency?
A: When you need very clean output voltage with low noise, simple design, or when the voltage difference is small (high efficiency scenario).
Q4: Does this calculation account for quiescent current?
A: No, this is a simplified calculation. For very precise efficiency measurements, quiescent current and load current should be considered.
Q5: What's the maximum possible LDO efficiency?
A: The theoretical maximum is when Vout = Vin (100%), but in practice there are always small losses.