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LM338 Regulator: Pinout, Circuit, and Alternatives

This article explores the LM338 voltage regulator, celebrated for its versatility and robust performance across a variety of electronic applications. It provides adjustable output voltage and supports loads up to 5 amperes for a wide range of technical projects. Here, we delve into the LM338's features, its practical applications, and the technical specifics that underpin its widespread admiration and use.

Catalog

1. What is the LM338 Voltage Regulator?

2. LM338 Pin Configuration

3. LM338 Symbol, Footprint, and CAD Model

4. Features of the LM338

5. LM338 Technical Specifications

6. LM338 Alternatives and Equivalents

7. Functional Diagram of LM338

8. LM338 Layout Design

9. Circuits of the LM338

10. Applications of the LM338

11. LM338 Packaging

12. LM338 Manufacturer Information

What is the LM338 Voltage Regulator?

The LM338 emerges as a multifaceted three-terminal positive voltage regulator, housed conveniently in a TO-220 package. Its primary purpose is to deliver a consistent, adjustable output voltage between 1.2V and 32V DC. It functions optimally with an input capacity reaching up to 40V and is frequently deployed in environments that demand precise voltage stabilization. The operational principle mandates maintaining an input voltage consistently 2-3V higher than the desired output level. For example, to achieve stable 5V output, a minimum input of 7V is required, providing robustness during input fluctuations. This consideration holds in scenarios utilizing battery-operated devices or variable load power supplies.

The LM338 possesses the capability to deliver current outputs of up to 5A, making it a preferred option in circumstances where the LM317's current limitations become apparent. It becomes beneficial for high-current requirements in power amplifiers and high-power LED applications. A compelling trait of this regulator is its minimal need for external components, only two capacitors and two resistors are required, enabling precise output voltage adjustments. Calculating the necessary resistor values can be conveniently done using online tools, ensuring accuracy and efficiency across various electronic applications.

LM338 Pin Configuration

LM338 Pinout

PIN			I/O	DESCRIPTION
NAME	TO-220	TO-CAN	I/O	DESCRIPTION
ADJ	1	1	I	Output voltage adjustment pin. Connect to a resistor divider to set V_O
V_IN	3	2	I	Supply input pin
V_OUT	2	Case	O	Voltage output pin

LM338 Symbol, Footprint, and CAD Model

LM338 Symbol

LM338 Footprint

LM338 CAD Model

Features of the LM338

Output Current Capabilities

The LM338 stands out due to its ability to deliver a steady output current of up to 5A, with peaks reaching 7A. This makes it a robust choice for varied demanding applications, ensuring continuous and reliable power. Many have valued this ability to perform under continuous load, finding it reassuring in scenarios where performance must remain unfaltering.

Adjustable Output Voltage Range

The LM338 offers a flexible voltage range, adjustable from 1.2V to 32V, catering to diverse application demands. This adaptability allows for precise voltage tuning, greatly admired in customized electronic designs. Pondering over the potential applications that can benefit from this range often inspires its use in creative endeavors, such as bespoke power units or systems requiring variable voltage control.

Protective Safeguards

The component features essential safeguards, including short-circuit protection and thermal shutdown, which enhance its safety and lifespan. These mechanisms act as deterrents against adverse conditions, shielding the circuitry from unforeseen anomalies. In environments where circuit stability is under frequent trial, these protective features have served as shields to protect investments with confidence.

Design Simplicity

Encased in a TO-220 package, the LM338 necessitates minimal external components, needing just two resistors for output adjustment. This straightforward design reduces the complexity of its application and cuts costs for both commercial and personal projects. Others have often lauded this seamless integration, which simplifies the process while preserving full functionality.

Compliance and Reliability Aspects

Adherence to RoHS3 standards highlights the LM338's dedication to environmental safety, while its assured thermal regulation and consistent current limits signify reliability. Multiple projects have reaped the rewards of these assurances, offering insights into the influence of advanced regulations on product development timelines and market accessibility. As the drive for environmentally friendly electronics progresses, such compliance aligns eco-consciousness with dependable industry-grade solutions.

LM338 Technical Specifications

Technical specifications, characteristics, and parameters of the Texas Instruments LM338, along with components that match or closely resemble the specifications of the LM338T/NOPB.

Type	Parameter
Lifecycle Status	ACTIVE (Last Updated: 3 days ago)
Contact Plating	Tin
Mounting Type	Through Hole
Number of Pins	3
Operating Temperature	0°C~125°C
JESD-609 Code	e3
Part Status	Active
Number of Terminations	3
ECCN Code	EAR99
Max Power Dissipation	25W
Number of Functions	1
Current Rating	5A
Pin Count	3
Output Voltage	37V
Max Output Current	5A
Min Supply Voltage	3V
Factory Lead Time	6 Weeks
Mount	Through Hole
Package / Case	TO-220-3
Weight	2.298097g
Packaging	Tube
Pbfree Code	yes
Moisture Sensitivity Level (MSL)	1 (Unlimited)
Termination	Through Hole
Power Rating	25W
Terminal Position	SINGLE
Terminal Pitch	2.54mm
Base Part Number	LM338
Number of Outputs	1
Output Type	Adjustable
Max Supply Voltage	40V
Output Configuration	Positive
Power Dissipation	25W
Max Output Voltage	37V
Min Input Voltage	4.2V
PSRR	75dB ~ 60dB (120Hz)
Dropout Voltage	3mV
Min Output Voltage	1.2V
Load Regulation-Max(%)	1%
Height	4.7mm
Width	10.16mm
REACH SVHC	No SVHC
RoHS Status	ROHS3 Compliant
Quiescent Current	3mA
Voltage - Output (Min/Fixed)	1.24V
Protection Features	Over Temperature, Short Circuit
Reference Voltage	1.29V
Dropout Voltage1-Nom	2.7V
Power Supply Rejection Ratio (PSRR)	75dB
Line Regulation-Max (%)	0.08%
Length	14.988mm
Thickness	4.572mm
Radiation Hardening	No
Lead Free	Lead Free

LM338 Alternatives and Equivalents

Part Number	Description	Manufacturer
LM338N-1	2.2W, 1 CHANNEL, AUDIO AMPLIFIER, PDIP14	Texas Instruments
NJM386M-(T1)	Audio Amplifier, 0.5W, 1 Channel(s), 1 Func, Bipolar, PDSO8, DMP-8	New Japan Radio Co Ltd
NJM386M-(T2)	Audio Amplifier, 0.5W, 1 Channel(s), 1 Func, Bipolar, PDSO8, DMP-8	New Japan Radio Co Ltd
NJM386M-(TE2)	Audio Amplifier, 0.5W, 1 Channel(s), 1 Func, Bipolar, PDSO8, DMP-8	New Japan Radio Co Ltd
NJM386M-(TE1)	Audio Amplifier, 0.5W, 1 Channel(s), 1 Func, Bipolar, PDSO8, DMP-8	New Japan Radio Co Ltd
NJM386M-(TE3)	Audio Amplifier, 0.5W, 1 Channel(s), 1 Func, Bipolar, PDSO8, DMP-8	New Japan Radio Co Ltd
NJM386M-(TE4)	Audio Amplifier, 0.5W, 1 Channel(s), 1 Func, Bipolar, PDSO8, DMP-8	New Japan Radio Co Ltd
LM338T/NOPB	TO-220-3, Max Output Current 5 A, Min Input Voltage 4.2 V, Min Output Voltage 1.2 V, Dropout Voltage 3 mV	Texas Instruments
LM317BTG	TO-220-3, Max Output Current 500 mA, Min Input Voltage 4.2 V, Min Output Voltage 1.2 V, Dropout Voltage 2.1 V	ON Semiconductor
LM217T	TO-220-3, Max Output Current 400 mA, Min Input Voltage 4.2 V, Min Output Voltage 1.2 V, Dropout Voltage 1.95 V	STMicroelectronics
LM317TG	TO-220-3, Max Output Current 400 mA, Min Input Voltage 4.2 V, Min Output Voltage 1.2 V, Dropout Voltage 2.25 V	ON Semiconductor
LM317MBTG	TO-220-3, Max Output Current 1.5 A, Min Input Voltage 4.2 V, Min Output Voltage 1.2 V, Dropout Voltage -	ON Semiconductor

Functional Diagram of LM338

LM338 Functional Block Diagram

LM338 Layout Design

LM338 Layout

Circuits of the LM338

5A Current Regulator Circuit

12-V Battery Charger Circuit

Applications of the LM338

Commercial and Educational Power Supplies

The integration of the LM338 in commercial and educational settings is driven by its adeptness at flexible voltage regulation, playing a role in electronic laboratories and classrooms. These power supplies offer a dependable energy source, nurturing the budding curiosity of young minds in classrooms and refining the precision required in electronic lab settings. In commercial environments, they serve to elevate equipment performance with unwavering voltage delivery, subtly reinforcing the commitment to quality that underpins successful operational outcomes.

Laboratory Power Equipment

Laboratory settings thrive on precision and stability in power sources when conducting intricate experiments or testing electronic circuits. The LM338, with its unwavering voltage output, stands as a main component in these demanding scenarios. Researchers find satisfaction in the small voltage adjustments made possible by the LM338, knowing these tweaks can catalyze groundbreaking results, thereby supporting the spirit of innovation and discovery.

Voltage Step-Down Circuits

Adapting higher voltage levels to be compatible with delicate electronic components is a delicate task, where voltage step-down circuits become important. The LM338 shines brightly in these applications, ensuring seamless voltage reduction and safeguarding components from potential harm due to voltage irregularities. Particularly in industrial automation, where equipment reliability lies at the heart of operations, these features gain even greater significance.

Battery Chargers

In efficient battery charger design, the LM338 offers customizable output tailored to various battery types. Its prowess in regulating charging currents and voltages directly influences the extension of battery life and performance. Harnessing the LM338 can elevate a standard charger to one that optimizes charging, ultimately prolonging the lifecycle of the device.

Solar Power Solutions

As renewable energy gains traction, the role of the LM338 in solar power solutions becomes more pronounced. It assists in converting and stabilizing voltage sourced from solar panels, contributing to the enhancement of solar system efficiency and reliability. With renewable energy emerging as a nod to sustainable futures, the LM338’s flexibility and resilience in balancing fluctuating solar outputs support this transition toward sustainable solutions.

Microcontroller Setups

Precise voltage levels are important in microcontroller setups to ensure seamless performance. The LM338 rises to this challenge by providing adaptable power supply solutions to meet diverse microcontroller needs. Whether in prototyping stages or final projects, its versatility stands out.

DC-DC Converters

Serving as a robust element within DC-DC converters, the LM338 facilitates transitions between differing technologies with minimal energy expenditure. This capability becomes use in complex systems where conserving efficiency and reducing thermal impact is needed. Integrating the LM338 optimizes operational processes, reflected in cost savings and bolstered system performance.

Portable Instruments

In the design of portable instruments, the balance of weight, size, and power efficiency is of utmost consideration. The LM338 fits seamlessly into this balance, offering compact, efficient voltage regulation suited to portable applications across various disciplines. From medical equipment to mobile testing devices, the LM338 ensures reliable functionality across an array of challenging environments.

Adjustable Power Supplies

The LM338 plays a role in developing adjustable power supplies tailored to specific application demands. These supplies prove invaluable in testing and development phases, providing with the freedom to explore the ideal operating conditions for a multitude of devices. Through a nuanced approach to power management, the LM338 aids in fostering a wide spectrum of technical innovations.

LM338 Packaging

LM338 Package

LM338 Manufacturer Information

Texas Instruments stands out as a leading semiconductor firm, renowned for its cutting-edge development of analog chips and embedded processors. The company's product range, prominently featuring the widely appreciated LM338, highlights its influential role in the global semiconductor arena. With around 45,000 patents spanning the globe, TI’s unfaltering commitment to innovation glaringly showcases its technological prowess. Texas Instruments' remarkable legacy of innovation, combined with its contributions to technology advancement, anchors it as a pillar of the industry. The steadfast pursuit of excellence and tangible applications establishes an energetic atmosphere primed for ongoing triumph and evolution.

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Frequently Asked Questions [FAQ]

1. What is the difference between the LM138 chip and the LM338 chip? Are the parameters the same?

The LM138 and LM338 integrated circuits share many core performance traits but differ notably in their resistance to temperature variations. The LM138 is crafted to perform reliably over a wide temperature range from -55°C to 150°C, providing enhanced dependability in demanding conditions. The LM338, in contrast, operates effectively within 0°C to 125°C. This divergence highlights the necessity of choosing the right IC based on environmental context. In practical applications, being able to endure extreme temperatures can significantly affect the performance and lifespan of electronic systems.

2. What are the precautions for the use of LM338?

Heatsinking: To counter the substantial power dissipation, solid heatsinking is needed. This not only sustains device performance but also reduces potential degradation over time.

Capacitive Filtering: Employ large filter capacitors alongside smaller parallel ones to efficiently mitigate high-frequency noise. This is good for circuit stability, a lesson often learned, working with delicate electronics.

Output Load Handling: Direct connections of large capacitive loads to the output are ill-advised due to potential protection circuit complications. Others shows that using indirect connections or buffering can effectively manage these concerns.

3. What are the advantages and disadvantages of LM338 and LM317 as an adjustable power supply?

Current Capability: With a robust 5A current output, the LM338 is suited for high-power tasks, whereas the LM317 provides 1.5A, ideal for applications requiring less power.

Voltage Range: Although the LM317 provides a wider output voltage range of 1.2V to 37V, the LM338 adeptly handles needs within its 1.2V to 32V range, striking a precise balance for various regulatory purposes.

Input-Output Voltage Margin: The LM317 slightly excels with a higher maximum input-output voltage differential, offering a slight competitive edge in certain technical scenarios demanding high flexibility.

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