LDO Dropout Voltage Calculator
Calculate LDO minimum input voltage from dropout specification, determine power dissipation, and estimate efficiency at a given supply voltage.
Formula
How It Works
Low Dropout (LDO) regulators are linear voltage regulators designed to provide a stable output voltage with minimal voltage difference between input and output. Unlike traditional linear regulators, LDOs can operate with a very small dropout voltage, typically less than 300mV. This makes them ideal for battery-powered and low-voltage applications where efficiency and minimal power loss are critical.
Worked Example
Problem: Calculate the minimum input voltage and power dissipation for an LDO regulator with 3.3V output, 200mV dropout voltage, and 500mA load current. Solution: 1. Minimum Input Voltage (Vin_min): 3.3V + 0.2V + (0.5A × internal RDS(on)) 2. Power Dissipation: Pd = (Vin - 3.3V) × 0.5A 3. Assuming RDS(on) = 0.1Ω, Vin_min = 3.3V + 0.2V + (0.5A × 0.1Ω) = 3.35V 4. Power Dissipation: Pd = (3.35V - 3.3V) × 0.5A = 0.025W
Practical Tips
- ✓Always ensure input voltage is higher than output voltage plus dropout voltage
- ✓Consider heat dissipation and thermal design when selecting an LDO
- ✓Choose LDOs with low RDS(on) for better efficiency
Common Mistakes
- ✗Neglecting the dropout voltage in input voltage calculations
- ✗Overlooking the power dissipation impact on thermal management
- ✗Not considering the internal resistance of the LDO
Frequently Asked Questions
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