# LDO Efficiency Calculator

This tool calculates the efficiency (%) of a Low Drop Out (LDO) regulator.

Enter the

• Input Voltage
• Output Voltage
• Output Current
• Quiescent Current

Use the drop down menu to pick the appropriate units.

## Formula

PIN = VIN *(IIN) = VIN *(IOUT + IQ)

POUT = VOUT *(IOUT)

η = POUT/PIN

where

• PIN is the input power
• POUT is the output power
• VOUT is the output voltage
• VIN is the input voltage
• IOUT is the output current
• IIN is the input current
• IQ is the LDO’s quiescent current, defined as the current drawn by the chip in a no-load but enabled condition.

## Example Calculation

If the input voltage is 5 V and output is 3.3 V, output current is 150 mA and quiescent current is 0.25 mA. The efficiency in this case is 66%.

If the output current is smaller, at 1 mA, the efficiency drops to about 53%.

## Background

LDO’s are a type of linear voltage regulator that are designed to efficiently regulate the output voltage to a level slightly lower than the input voltage, while minimizing power dissipation. The picture below shows a commonly used LDO.

LDO’s offer several advantages such as low output noise, simplicity, and accuracy in voltage regulation. However, they also have limitations including slower transient response and higher power dissipation compared to switching regulators.

In the field of electronics and electrical engineering, understanding the efficiency of Low-Dropout (LDO) regulators is important for designing reliable and effective power supply systems. This calculator helps estimate that quantity.