Phone

    00852-6915 1330

LM338 Voltage Regulator: Pinout, Datasheet, Circuit [FAQ]

  • Contents

LM338 is an adjustable 3-terminal positive voltage regulator which capable of supplying in excess of 5A over a 1.2V to 32V output range.

 

This blog will introduce LM338 from its pinout, features to its application circuits, datasheet and including some other information.


Catalog

LM338 Description

LM338 Pinout

LM338 Features

LM338 Parameter

LM338 Functional Block Diagram

LM338 Schematic Diagram

LM338 Circuit

LM338 Application

LM338 Package

LM338 Manufacturer

Component Datasheet

FAQ


LM338 Description

The LM338 is an adjustable 3-terminal positive voltage regulator which capable of supplying in excess of 5A over a 1.2-V to 32-V output range. It is exceptionally easy to use and require only 2 resistors to set the output voltage. Careful circuit design has resulted in outstanding load and line regulation, comparable to many commercial power supplies.

 

The LM338 voltage regulator offers full overload protection.

 

The LM338 supplied in a standard 3-lead transistor package.

 

Normally, no capacitors are needed unless the device is situated more than 150 mm (6 inches) from the input filter capacitors in which case an input bypass capacitor is required. An optional output capacitor can be added to improve transient response. The adjustment terminal of the regulator can be bypassed to achieve very high ripple rejection. Refer to the adjustable regulator data sheets below for more information about the LM338 adjustable voltage regulator.


LM338 Pinout

LM338 voltage regulator lm338 voltage regulator pinout
LM338 LM338 Pinout

LM338 Features

  • Specified 7-A Peak Output Current

  • Specified 5-A Output Current

  • Adjustable Output Down to 1.2 V

  • Specified Thermal Regulation

  • Current Limit Constant With Temperature

  • P+ Product Enhancement Tested

  • Output is Short-Circuit Protected


LM338 Parameter

Manufacturer: Texas Instruments
Series: -
Packaging: Tube
Part Status: Active
Output Configuration: Positive
Output Type: Adjustable
Number of Regulators: 1
Voltage - Input (Max): 40V
Voltage - Output (Min/Fixed): 1.24V
Voltage - Output (Max): 32V
Voltage Dropout (Max): -
Current - Output: 5A
PSRR: 75dB ~ 60dB (120Hz)
Control Features: -
Protection Features: Over Temperature Short Circuit
Operating Temperature: 0°C ~ 125°C
Mounting Type: Through Hole
Package / Case: TO-220-3
Supplier Device Package: TO-220-3
Base Part Number: LM338

LM338 Functional Block Diagram

LM338 Functional Block Diagram


LM338 Schematic Diagram

You can use this Voltage Regulator Calculator to vary the value of the program resistor (R1) and output set resistor (R2) and calculate the output voltage for the LM338 of three terminal adjustable voltage regulator.

 

This Voltage Regulator Calculator will work for all voltage regulators with a reference voltage (VREF) of 1.25. For the LM338 and LM350 regulators, 120 ohms is typically used for the program resistor R1. However, other values such as 150 or 220 ohms can also be used for R1. The LM338 voltage regulator can also be configured to regulate current in a circuit.

LM338 Schematic diagram

LM338 Schematic diagram


LM338 Circuit

The following schematics show typical circuit applications for the LM338 voltage regulator.

Note: The dropout voltage of the IC regulator is about 1.5 to 2.5 Volts, depend on the output current (IOUT). Therefore, the input voltage to the  LM338 regulator will need to be at least 1.5V to 2.5V greater than the desired output voltage. Plan to be about 3V of  the desired output voltage. You don't want to use too high an input voltage as the excess will need to be dissipated as heat through the regulator.  See the datasheets of the voltage regulator above for specific details on the voltage drop-off and heatsink requirements.

Figure 1. 1.2 to 25V Adjustable Voltage Regulator

Figure 1. 1.2 to 25V Adjustable Voltage Regulator

When using external capacitors with a voltage regulator it may be necessary to use protection diodes to prevent the capacitors from discharging through low current points into the voltage regulator. Even small capacitors can have a low enough internal series resistance to be able to deliver 20A spikes when shortened. Although the surge is very short in duration, there is enough energy to damage parts of the regulator IC. No protection diodes are required for output voltages of less than 25V or greater than 10 uF capacitance. Figure 2 shows the LM338 with protection diodes included for use with voltage outputs greater than 25V and high values of output capacitance.

Figure 2. Adjustable Voltage Regulator with Protection Diodes

Figure 2. Adjustable Voltage Regulator with Protection Diodes

Solid tantalum capacitors can be used on the voltage output to improve the ripple rejection of the voltage regulator.

Figure 3. Adjustable Voltage Regulator with Improved Ripple Rejection

Figure 3. Adjustable Voltage Regulator with Improved Ripple Rejection


LM338 Application

  • Adjustable Power Supplies

  • Constant Current Regulators

  • Battery Chargers


LM338 Package

LM338 Package


LM338 Manufacturer

Texas Instruments Incorporated (TI) is an American technology company headquartered in Dallas, Texas, that designs and manufactures semiconductors and various integrated circuits, which it sells to electronics designers and manufacturers globally. It is one of the top 10 semiconductor companies worldwide based on sales volume. The company's focus is on developing analog chips and embedded processors, which account for more than 80% of its revenue. TI also produces TI digital light processing technology and education technology products including calculators, microcontrollers and multi-core processors. The company holds 45,000 patents worldwide as of 2016.


Component Datasheet

LM338 Voltage Regulator Datasheet


FAQ

  • What is lm338?

The LM138/LM238/LM338 are adjustable 3-terminal positive voltage regulators capable of supplying in excess of 5A over a 1.2V to 32V output range.

  • What is the current rating of voltage regulator IC LM338 K?

The LM317 / LM338 / LM350 family of adjustable 3-terminal positive voltage regulators can take a input of 3 to 40 Volts DC and provide a regulated voltage over a 1.2V to 37V output range. The LM317 voltage regulators can provide up to 1.5 Amperes (A) of output current.

  • What is adjustable voltage regulator?

An adjustable voltage regulator produces a DC output voltage, which can be adjusted to any other value of certain voltage range. Hence, adjustable voltage regulator is also called as a variable voltage regulator. The DC output voltage value of an adjustable voltage regulator can be either positive or negative.

  • What is function of voltage regulator?

A voltage regulator generates a fixed output voltage of a preset magnitude that remains constant regardless of changes to its input voltage or load conditions. There are two types of voltage regulators: linear and switching.

  • How do you test a voltage regulator?

The best way to test a voltage regulator is with a multimeter, and what you do is you put your multimeter clamps directly on the battery terminals. Positive read to positive and black to negative. And you said it to voltage, and with the car off, you should have a little over 12 volts. That's that's a healthy battery.

 

Kynix

Kynix was founded in 2008, specializing in the electronic components distribution business. We adhere to honesty and ethics as our business philosophy and have gradually established an excellent reputation and credibility in our international business. With the accurate quotation, excellent credit, reasonable price, reliable quality, fast delivery, and authentic service, we have won the praise of the majority of customers.

Join our mailing list!

Be the first to know about new products, special offers, and more.

Leave a Reply

We'd love to hear from you! Feel free to share your thoughts and comments below. Rest assured, your email address will remain private.

Name *
Email *
Captcha *
Rating:

Kynix

  • How to purchase

  • Order
  • Search & Inquiry
  • Shipping & Tracking
  • Payment Methods
  • Contact Us

  • Tel: 00852-6915 1330
  • Email: info@kynix.com
  • Follow Us

authentication

Kynix

© 2008-2026 kynix.com all rights reserved.