LDO Linear Regulator Dropout Calculator
Calculate LDO regulator power dissipation, junction temperature rise, minimum input voltage, efficiency, and headroom for linear regulator design
Formula
P_D = (V_in − V_out) × I_load, η = V_out / V_in × 100%
How It Works
An LDO (Low Dropout) linear regulator is a voltage regulation device that can maintain a stable output voltage with a very small difference between input and output voltage. The dropout voltage represents the minimum voltage difference required for the regulator to maintain proper regulation. In practical electronic design, understanding and calculating dropout voltage is crucial for efficient power management, especially in battery-powered and low-voltage applications. Linear regulators work by dissipating excess input voltage as heat, with LDO regulators being more efficient due to their ability to operate with minimal voltage overhead.
Worked Example
Example Calculation: For an LDO regulator with a 5V input and 3.3V desired output, calculate the dropout voltage. Assume the regulator's specified dropout voltage is 300mV. Input Voltage (Vin) = 5V, Desired Output Voltage (Vout) = 3.3V, Dropout Voltage (Vdropout) = 0.3V. Verify regulation by confirming: Vin - Vout ≥ Vdropout (5V - 3.3V = 1.7V > 0.3V), which confirms the regulator can maintain stable output.
Practical Tips
- ✓Always ensure input voltage is at least the dropout voltage plus desired output voltage
- ✓Consider thermal management as dropout voltage directly impacts power dissipation
- ✓Choose LDO regulators with low dropout voltage for battery-powered designs
- ✓Check the regulator's maximum current rating for your specific load requirements
Common Mistakes
- ✗Selecting a regulator with dropout voltage too close to the input-output voltage difference
- ✗Neglecting current requirements when choosing an LDO regulator
- ✗Ignoring thermal considerations in power design
Frequently Asked Questions
What is dropout voltage?
Dropout voltage is the minimum voltage difference required between input and output for a linear voltage regulator to maintain a stable output voltage.
Why is low dropout voltage important?
Low dropout voltage enables more efficient power conversion, reduces heat generation, and allows operation with minimal voltage overhead in battery and low-voltage systems.
How do I calculate the required input voltage for an LDO?
Calculate by adding the desired output voltage, the dropout voltage, and any voltage tolerance margins specified by the regulator's datasheet.
Shop Components
Affiliate links — we may earn a commission at no cost to you.
Related Calculators
Power
MOSFET Power Loss
Calculate MOSFET conduction loss, switching loss, total power dissipation, junction temperature, and efficiency for power electronics design
Thermal
Thermal Resistance Network
Calculate junction, case, and heatsink temperatures through a series thermal resistance network (θJC + θCS + θSA) for component thermal management
Power
Switching Regulator Ripple
Calculate buck converter output voltage ripple, inductor current ripple, and ESR contribution for switching regulator design
Power
Voltage Divider
Calculate voltage divider output voltage, current, Thévenin impedance, and power dissipation from Vin, R1, and R2. Ideal for bias networks and level shifting.
Power
LED Resistor
Calculate the correct current limiting resistor for an LED. Shows exact value, nearest E24 standard, actual current, and power dissipation.
Power
Buck Converter
Design a synchronous buck (step-down) converter: calculate duty cycle, inductor value, output capacitor, input capacitor, and theoretical efficiency.