Calculadora de Regulador LDO
Disipación de potencia y análisis térmico
Required Parameters
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Quick Answer
LDO calculator: P = (Vin − Vout) × Iload. Example 5 V→3.3 V @ 500 mA → 0.85 W heat. Check Tj = Ta + P×θJA stays below 125 °C.
LDO Calculator — Linear Regulator Thermal Design
Use this LDO calculator to check dropout, power dissipation, and junction temperature before you commit a linear regulator to the PCB.
Core formulas
| Quantity | Formula |
|---|---|
| Power dissipation | P = (Vin − Vout) × Iload |
| Junction temperature | Tj = Ta + P × θJA |
| Efficiency | η = Vout / Vin |
Worked example — 5 V → 3.3 V @ 500 mA
- Dropout: 5 − 3.3 = 1.7 V
- P = 1.7 × 0.5 = 0.85 W (all converted to heat)
- With θJA = 50 °C/W and Ta = 25 °C: Tj = 25 + 0.85×50 = 67.5 °C ✓
If the same load ran at 1 A, P = 1.7 W → Tj = 110 °C — still OK on many packages, but verify the datasheet curve.
When to use LDO vs buck
- LDO: low noise (ADC, RF, audio), small Vin−Vout (< 2 V), I < 500 mA
- Buck: battery-powered, large step-down, high current — 85–95% efficiency vs ~66% for 5→3.3 V LDO
Capacitor selection
- Output: 1–10 µF X5R/X7R ceramic, placed at the LDO output pin
- Input: 1–10 µF ceramic at the input pin — reduces source impedance during load steps
Related tools
- LDO Regulator Calculator — interactive thermal check
- Buck/Boost Converter Calculator — when efficiency matters
- Component Derating Calculator — cap voltage margin after regulation
- Electrical Power Calculator — P = VI verification
Design Notes
LDOs are simple but waste power as heat. Efficiency = Vout/Vin. For a 5V→3.3V conversion at 500mA, you dissipate 0.85W. Always check the dropout voltage spec at your load current — it increases with current. Use input and output capacitors (typically 1µF-10µF ceramic) for stability.
Common Mistakes
- 1
Forgetting that dropout voltage increases with load current — check the datasheet curves.
- 2
Ignoring thermal limits — a SOT-23 package can only dissipate ~0.4W without a heatsink.
- 3
Using an LDO where a switching regulator would be far more efficient (large Vin-Vout differential).
Engineering Handbox
1. Dropout = 5 − 3.3 = 1.7 V 2. P = 1.7 × 0.5 = 0.85 W 3. Tj = 25 + 0.85 × 50 = 67.5 °C
Knowledge Base
¿Qué es un regulador LDO?
Regulador lineal con diferencial mínimo de entrada-salida (100-500mV). Produce salida limpia con ruido mínimo, ideal para circuitos analógicos, ADC y etapas RF.
¿Cuándo usar LDO vs convertidor conmutado?
LDO: bajo ruido, Vin-Vout < 2V, corriente < 500mA. Conmutado: eficiencia, gran diferencial, alta corriente. Eficiencia LDO = Vout/Vin (3.3V desde 5V = 66%).
¿Cómo calculo la disipación del LDO?
P = (Vin - Vout) × Icarga. 5V a 3.3V a 500mA: P = 0.85W. Verificar Tj = Tamb + P×θJA < 125°C.
¿Qué LDOs son populares?
3.3V: AMS1117-3.3 (1A, barato), AP2112K (600mA, bajo ruido). Ajustable: LM317, TLV757P. Para batería: ME6211 (500mA, 100mV dropout, 40µA Iq).
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