HomeCalculatorsElectricalSemiconductorLDO Thermal Calculator
Electrical calculator

LDO Thermal Calculator

Compute LDO dissipation P=(Vin−Vout)·Iout (+ Iq·Vin) and junction temperature. Runs locally in your browser.

Instant result
Result
—

Enter values to calculate.

Inputs—
Mode—
Formula—
Trust summary CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance
Input interpretation
Enter values to calculate.
Result
—
Assurance
Engineering
Declared partition coverage
PASS · 2/2 declared partitions (nominal, invalid-domain) · Matrix
Known limitations
  • Steady-state lumped Rth; Vin>Vout required
  • Core CVP does not include live graph, viewport, or pointer interaction.
Model
LDO dissipation and Tj.
Scope
Steady-state lumped Rth
Verification
Engine tested · Source checked · v1.0.0 · CVP VERIFIED · CVP protocol 1.0.0-proposed · Engineering assurance· View Manifest · CVP overview · Specification
Versions
Calculation 1.0.0 · CVP protocol 1.0.0-proposed
CVP identity
1/1 property · digest d5b9917ab618
Legacy regression
3/3 tests · Production surface contract 4/4
Reference
O1 model · O2 expected_values · O2 numerical_behavior
Interfaces
PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session.
Supplemental domain review
Internal · Pass
Named expert review
Not performed
CVP suite
1/1 golden · 1/1 CVP boundary · 1/1 invalid · 1/1 property · 1/1 cross-interface · 1/1 CVP contract · Manifest
Sources
  • LDO thermal design notes — Power dissipation
  • JEDEC thermal characterization practice — θJA / Rth
Sources
Evidence
1 legacy golden · 1 legacy boundary · legacy regression suite · 1/1 oracle-backed golden · 1/1 invalid · Artifact integrity PASS · CalculatorX electrical review
This calculator CURRENT · Public schema 1.0.0 matches · Semantic contract ✓ · Production attested · Public/cache ✓ · Origin ✓
Semantic contract
PASS
Full verification

Manifest identity, reference classes, interfaces, suite, and production records.

Formulas

Core equations used by this calculator.

DissipationP = (Vin−Vout)·Iout + Iq·Vin
JunctionTj = Ta + P·Rth
iSteady-state. Not a dropout curve / PSRR model.

How to use

1

Enter Vin, Vout, and load current

Dropout power is (Vin−Vout)·Iout. Vin should exceed Vout.

2

Enter ambient temperature and Rth

Package/board thermal resistance from junction to ambient.

3

Optional: enter quiescent current Iq

Adds Iq·Vin to dissipation. Read P and estimated Tj.

Example calculations

Common configurations with formula and result.

ϟ

5→3.3 V · 0.5 A

Rth=50

0.85·50
Tj=67.5 °C @ Ta=25

LDO Thermal calculator specification

Version 1.0.0 · Engine tested · Supplemental domain review · Internal · 2026-08-09

Calculation status

Review policy · Evidence · Reviewed by CalculatorX electrical review

Definition
Pass-element power P_pass=(Vin−Vout)·Iout; optional quiescent P_q=Iq·Vin. Tj=Ta+P·Rth.
What it calculates
LDO dissipation and Tj.
Inputs
  • Vin
  • Vout
  • Iout
  • Ta
  • Rth
  • Iq?
Outputs
  • P_W
  • Tj_C
Formula
Tj=Ta+((Vin−Vout)Iout)·Rth
Assumptions
  • Steady-state lumped Rth
Units
  • V, A, °C, °C/W
Boundary conditions
  • Vin≤Vout → VALUE_OUT_OF_RANGE
Example
5→3.3 0.5A Rth=50 Ta=25 → Tj=67.5
Validation cases

1 published on this page · 3/3 tests · Production surface contract 4/4 · View evidence

  • Vin=5 Vout=3.3 Iout=0.5 Ta=25 Rth=50 → Tj=67.5
Sources
  • LDO thermal design notes — Power dissipation
    Supports: P=(Vin−Vout)·Iout
  • JEDEC thermal characterization practice — θJA / Rth
    Supports: Tj = Ta + P·Rth
Last reviewed
2026-08-09
Reviewed by
CalculatorX electrical review
Calculation version
1.0.0

Background

Interpretation and common distinctions.

Estimate LDO thermal dissipation and junction temperature.

Supported and not supported

Supported — Dissipation + Tj · API electrical.ldo.thermal

Not supported — Transient SOA, package θJA tables lookup

Agent / API notes

Capability id: electrical.ldo.thermal · tool id: ldo-thermal · pin 1.0.0.

Other calculators in this family: ADC Error Budget Calculator, Diode Equation Calculator, LED Resistor Calculator, MOSFET Conduction Loss Calculator, MOSFET Junction Temperature Calculator, MOSFET Switching Loss Calculator, MOSFET Threshold & Overdrive Calculator, MOSFET Total Loss Calculator . Explore all Semiconductor.

→ ADC Error Budget Calculator Combine ADC gain, offset, INL, and DNL errors (RSS or worst-case) into total LSB, volts, and %FS. Runs locally in your browser. › → Diode Equation Calculator Shockley diode law I_D=I_S·(e^(V_D/(n·V_T))−1). Solve current or voltage, including reverse branch I_D > −I_S. Runs locally in your browser. › → LED Resistor Calculator Size the series resistor for one or more LEDs: R = (Vs − n·Vf) / If. › → MOSFET Conduction Loss Calculator Calculate MOSFET conduction loss from I, Rds(on), current definition (DC / on-interval RMS / full-cycle RMS), and optional Rds(Tj) via linear α or datasheet ratio. Runs locally in your browser. › → MOSFET Junction Temperature Calculator Estimate MOSFET junction temperature from ambient, dissipation, and thermal resistance (effective RθJA, or case/heatsink-dominant RθJC+RθCA). Optional thermal margin. › → MOSFET Switching Loss Calculator First-order hard-switching overlap loss P_sw = ½·Vds·Id·(tr+tf)·f_sw, plus optional gate-drive power Qg·Vdrive·f. Not a full MOSFET loss stack. Runs locally in your browser. › → MOSFET Threshold & Overdrive Calculator Calculate MOSFET overdrive Vod=Vgs−Vth, square-law drain current, or model Vth. Vth here is the long-channel square-law parameter — not datasheet VGS(th). Runs locally in your browser. › → MOSFET Total Loss Calculator MOSFET device dissipation from conduction + hard-switching + optional Coss/Eoss, plus optional gate-drive and Qrr commutation. Tj uses P_device, not associated total. Omitted terms are not treated as 0 W. Runs locally in your browser. ›
}

Frequently asked questions

Key distinctions behind the calculation.

Include Iq?

Optional. Leave Iq at 0 if you only care about load dissipation.