LM2940T-5Fixed +5 V low-dropout regulator

A regulated +5 V rail with three electrical connections.

Manufacturer-referenced

Texas Instruments · LM2940CT-5.0/NOPB

TO-220SNVS769J · December 2014

LM2940T-5 is a three-terminal regulator that produces a nominal +5 V output from a higher positive DC source. This page selects LM2940CT-5.0/NOPB in TO-220 and LM2940CS-5.0/NOPB in its surface-mount package. The internal reference, feedback amplifier and series pass device form the voltage-control loop. The LM2940C uses a low-dropout pass stage, but its output capacitor is part of the stability design. Use at least 22 µF effective capacitance with ESR in the manufacturer’s permitted range across load and temperature. An arbitrary low-ESR ceramic substitution can oscillate. The illustrated +7.5 V-to-+5 V supply drives a 50 Ω load at approximately 100 mA. The load dissipates 0.50 W and the pass stage loses about 0.25 W before ground-current losses. All package views follow the selected part; the example is a DC circuit reference, not a live simulation.

Real View

LM2940CT-5.0/NOPB black regulator with formed silver leads and centered identification.

Pinout

LM2940T-5TO-220Front view · marking toward you · leads down

PCB Footprint

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3D View

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3Physical pins LM2940CT-5.0/NOPBTO-220 Manufacturer-referencedTexas Instruments

Pin diagram

Select a pin to explore its connection

Package map

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LM2940T-5TO-220Front view · marking toward you · leads down

Click a lead or use the arrow keys. Front view · marking toward you · leads down

PIN 1 · Supply

INPUT

Supply input

Function

Feeds the series pass stage.

How to connect

Apply +7.5 V and fit 0.47 µF local input bypass.

Key specifications

A regulated +5 V rail with three electrical connections.

Regulated output+5 V nominal

Selected C-grade range0–125 °C · see manufacturer conditions

Current class1 A · thermal limits apply

Connections3 IN 1 · GND 2 · OUT 3

Package details

LM2940CT-5.0/NOPB · TO-220

Selected package

Selected LM2940T-5 physical package
Property	Details
Manufacturer	Texas Instruments
Part number	LM2940CT-5.0/NOPB
Package	TO-220
Connections	3 pins
Mounting	Through-hole
Lead pitch	2.54 mm
Package code	V
Thermal reference	Check the manufacturer package and mounting conditions

Package connections

Front view, marking toward you

Manufacturer specifications 3 parameters

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Parameter	Value	Conditions / notes
1 · INPUT	Feeds the series pass stage.	Apply +7.5 V and fit 0.47 µF local input bypass.
2 · GND	Metal tab is electrically GND.	Join supply return, load and capacitor returns.
3 · OUTPUT	Supplies nominal +5 V within regulation and thermal limits.	Connect the load and 22 µF to ground.

The exposed tab duplicates pin 2. Verify polarity before applying power.

Operating characteristics

LM2940CT-5.0/NOPB / LM2940CS-5.0/NOPB

Manufacturer specifications 7 parameters

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Parameter	Value	Conditions / notes
Output at 25°C	4.85–5.15 V	5 mA–1 A; specified input range
Output across stated range	4.75–5.25 V	5 mA–1 A; selected C grade
Input for 5 V regulation specification	6.25–26 V	More specific than family headline
Load regulation	35 mV typical; 50 mV max	50 mA–1 A; LM2940C
Ground current at 1 A	30 mA typical; 45 mA max at 25°C	VIN = VOUT + 5 V; 60 mA max over temperature
Output noise	150 µV RMS typical	10 Hz–100 kHz; 5 mA
Ripple rejection	72 dB typical; 60 dB min	120 Hz; 100 mA; LM2940C

Read the exact test conditions. Typical values are not guaranteed limits.

Capacitors and connections

Local components near the regulator

Manufacturer specifications 5 parameters

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Parameter	Value	Conditions / notes
Input bypass	0.47 µF	IN 1 to GND 2
Output capacitor	22 µF	OUT 3 to GND 2
Capacitor selection	At least 22 µF, ESR 0.1–1 Ω	Maintain effective capacitance and ESR across temperature
Tab / thermal pad	GND	Electrically connected to pin 2
Dropout	0.5 V typical; 0.8 V max at 1 A, 25°C; 1 V max over temperature	Not an unconditional fixed input margin

Short return paths and correct capacitor characteristics matter.

Basic circuit and readings

100 mA nominal DC load

Manufacturer specifications 6 parameters

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Parameter	Value	Conditions / notes
Input / output	+7.5 V / +5 V	DC source with sufficient headroom
Load	50 Ω	Dissipation 0.50 W; choose adequate derating
Current	5 V / 50 Ω = 0.10 A	Nominal calculation
Pass loss	0.25 W	(7.5 − 5) V × 0.10 A
Total regulator loss	Pass loss + \|VIN\| × IGND	Ground current also produces heat
Cooling	TJ ≈ TA + PD × θJA	Use thermal resistance for actual mounting

Respect resistor rating, input ripple and regulator dissipation.

Package and stress reference

LM2940CT-5.0/NOPB · TO-220

Manufacturer specifications 5 parameters

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Parameter	Value	Conditions / notes
Lead pitch	2.54 mm	Through-hole
Selected temperature grade	0–125°C	LM2940C; other LM2940-N grades differ
Input stress limit	26 V operating maximum; see transient limits	Do not use stress limits as a normal design target
Storage	−65 to +150°C	Unpowered
Package mapping	1 INPUT; 2 GND; 3 OUTPUT	Thermal pad duplicates pin 2

Verify the manufacturer package drawing and footprint before PCB manufacture.

Connections by function

Select a pin for its function, connection guidance and electrical notes.

Supply1 pin

Ground1 pin

Regulated output1 pin

LM2940T-5 working principle: illustrated functional stages, basic circuit and connections — Select the diagram to read it at full resolution.

How it works

3 stages · Explore one step at a time

Step 1 / 3

Reference

The internal reference establishes the desired output level.

Step 2 / 3

Regulate

The feedback amplifier controls the series pass stage.

Step 3 / 3

Dissipate heat

Voltage drop and ground current generate heat that must leave the package.

LM2940T-5 with +7.5 V input, +5 V output, 0.47 µF input bypass and 22 µF output capacitor. — Ground symbols share one return. Check capacitor requirements and thermal design.

Connect it, step by step

Follow the component values and pin connections

Connect input

Apply +7.5 V to pin 1.

Fit capacitors

Fit at least 22 µF with suitable ESR at the output.

Connect load

Connect 50 Ω from output to ground with adequate power rating.

LM2940T-5 internal functional cutaway with correct pin order. — Functional architecture, not a physical die layout.

Explore the circuit

Select a stage to see its role and connections

Sense

Compare output feedback with the reference.

Control

Adjust the pass stage.

Protect

Limit abnormal current and temperature.

Selected packageTO-220LM2940CT-5.0/NOPB

Physical connections3 pinsPackage-specific numbering

Reference collection6 tables26 parameters & pin functions