LM340T5 Voltage Regulator Everything You Need to Know

FREE-SKY (HK) ELECTRONICS CO.,LIMITED / 08-11 09:08

The LM340T5 is a three-terminal positive linear voltage regulator that converts a higher DC input voltage into a fixed and regulated 5 V output. Its three pins are Input, Ground, and Output, making it simple to connect and use. This article covers its specifications, pinout, working principle, application circuits, power dissipation, protection features, applications, comparisons, and possible replacements.

Catalog

1. LM340T5 Features and Specifications

2. LM340T5 Pinout and Pin Functions

3. LM340T5 Working Principle

4. LM340T5 Typical Application Circuits

5. LM340T5 Input Voltage Requirements

6. LM340T5 Output Current and Load Capacity

7. LM340T5 Power Dissipation and Heat-Sink Calculation

8. LM340T5 Protection and Safety Features

9. LM340T5 Applications

10. LM340T5 vs 7805 Voltage Regulator

11. LM340T5 vs LDO Regulator

12. LM340T5 vs Buck Converter

13. Equivalents and Replacements

14. Mechanical Dimensions

15. Manufacturer

LM340T5 Features and Specifications

Specification	LM340T5 Value
Regulator type	Positive linear voltage regulator
Output type	Fixed
Number of outputs	One
Nominal output voltage	5 V
Output voltage at 25°C	4.8 V to 5.2 V
Output voltage over operating conditions	4.75 V to 5.25 V
Rated test load	Specifications provided at up to 1 A
Maximum practical output current	Depends on input voltage, heat sinking, and operating temperature
Peak output current	2.4 A typical at 25°C
Short-circuit current	2.1 A typical at 25°C
Recommended input voltage	Approximately 7.5 V to 20 V for full specified regulation
Absolute maximum DC input voltage	35 V
Dropout voltage	2 V typical at 1 A and 25°C
Quiescent current	8 mA typical at 25°C
Maximum quiescent current	8.5 mA over the operating temperature range
Line regulation	3 mV typical, 50 mV maximum at 25°C under the specified test conditions
Load regulation	10 mV typical, 50 mV maximum at 25°C for a 5 mA to 1.5 A load change
Ripple rejection	62 dB minimum, 80 dB typical at 120 Hz
Output noise voltage	40 µV typical from 10 Hz to 100 kHz
Output resistance	8 mΩ typical at 1 kHz
Output temperature coefficient	−0.6 mV/°C typical
Minimum load used for full regulation specifications	5 mA
Operating temperature range	0°C to +125°C
Maximum junction temperature	150°C
Storage temperature range	−65°C to +150°C
Internal power dissipation	Internally limited
Junction-to-ambient thermal resistance	54°C/W for the TO-220 package without a heat sink
Junction-to-case thermal resistance	4°C/W for the TO-220 package
Thermal overload protection	Built in
Short-circuit current limiting	Built in
Safe-operating-area protection	Built in
ESD susceptibility	2 kV
Package type	Three-lead TO-220
Mounting type	Through-hole
Pin configuration	Pin 1 Input, Pin 2 Ground, Pin 3 Output
Output capacitor	Not required for basic stability, but 0.1 µF can improve transient response

LM340T5 Pinout & Pin Functions

Pin Number	Pin Name	Pin Function
1	Input	Connects to the positive unregulated DC input supply. The input voltage must remain high enough above 5 V to maintain proper regulation.
2	Ground	Connects to the circuit ground and serves as the reference point for the input and output voltages. The metal tab is also electrically connected to ground.
3	Output	Provides the regulated positive 5 V DC output to the load. An optional output capacitor can improve transient response.

LM340T5 Working Principle

The LM340AT-5.0/NOPB

Texas Instruments	Fixed 5 V	Up to 1.5 A	Direct replacement
UA7805CKCS	Texas Instruments	Fixed 5 V	Up to 1.5 A	Direct replacement
L7805ABV	STMicroelectronics	Fixed 5 V	Up to 1.5 A	Close replacement
MC7805ACTG	onsemi	Fixed 5 V	Up to 1 A	Close replacement
LM317T	Various	Adjustable	Up to 1.5 A	Not a direct replacement
5 V switching regulator module	Various	Fixed or adjustable 5 V	Model-dependent	Functional alternative

Mechanical Dimensions

Manufacturer

National Semiconductor originally manufactured the LM340T5 using its established analog semiconductor design, wafer fabrication, assembly, packaging, and electrical testing capabilities. The company produced the regulator in a three-pin TO-220 package and incorporated internal current limiting, thermal shutdown, and safe-operating-area protection to support reliable operation. Its manufacturing facilities included sites in the United States, Scotland, and Malaysia, supported by international design and sales operations. Texas Instruments completed its acquisition of National Semiconductor in September 2011, adding National’s analog products, technical expertise, and manufacturing capacity to TI’s Analog business.