LM338 5A Adjustable Positive Voltage Regulator TO-220

LM338 5A Adjustable Positive Voltage Regulator TO-220 is a high-current, precision linear regulator capable of delivering over 5 A of continuous load current across a wide output voltage range. This powerful IC simplifies the design of robust power supplies. Consequently, it provides a stable and easily adjustable output from 1.2 V to 32 V. Unlike fixed-voltage regulators, the LM338 requires only two external resistors to set the output voltage, offering exceptional flexibility for various applications. Furthermore, its integrated protection features—including current limiting, thermal shutdown, and safe operating area compensation—make it virtually impervious to typical overload conditions. Therefore, you can rely on the LM338 to efficiently manage power delivery in demanding electronic projects where high current and reliability are essential.

Key Features:

• High Output Current: The device guarantees delivery of a minimum of 5.0 A (I_OUT) over the entire output voltage range, accommodating high-power loads.
• Wide Adjustable Output: Users can set the output voltage from 1.2 V up to 32 V, making it extremely versatile for different system requirements.
• Excellent Load Regulation: The regulator maintains output voltage stability within a mere 0.3% maximum, even with significant changes in the load current.
• Thermal and Overload Protection: Integrated thermal limiting and short-circuit protection safeguards the IC against extreme operating conditions and accidental faults.
• Standard TO-220 Package: The industry-standard TO-220 package simplifies mounting to heat sinks for effective thermal management under heavy loads.

Technical Specifications:

• Output Current (I_OUT): 5 A minimum guaranteed, 7 A peak
• Output Voltage Range (V_OUT): 1.2 V to 32 V
• Input Voltage Range (V_IN): Up to 35 V maximum
• Reference Voltage (V_REF): 1.25 V (±2% tolerance)
• Line Regulation: 0.005% per V (typical)
• Temperature Stability: 0.01% per °C
• Dropout Voltage: Typically 3 V at 5 A
• Operating Temperature Range: −40°C to +125°C (Junction Temperature)

Mechanical Specifications:

• Package Type: TO-220 (Plastic Power Package)
• Leads: 3-Pin, Through-Hole
• Mounting: Requires a heat sink for sustained high-current operation (mounting hole provided).
• Lead Material: Solder-plated copper alloy

Dimensions:

• Body Length (excluding leads): ≈ 10.16 mm
• Body Width: ≈ 4.5 mm
• Lead Pitch (Center-to-Center): 2.54 mm (0.1 inch)
• Total Height (including heat sink tab): ≈ 15.6 mm
• Thermal Resistance (Junction to Case): Typically 4.0 °C/W

Pinout and Wiring:

• Pin 1 (Adjust): Connect this pin to the resistor divider network that sets the output voltage (V_OUT).
• Pin 2 (V_OUT): This pin provides the regulated output voltage to the load. It is electrically connected to the metal tab/heat sink.
• Pin 3 (V_IN): Connect the unregulated input DC voltage (V_IN) to this pin.
• Wiring Note: Always include decoupling capacitors (C_IN and C_OUT) close to the regulator pins to maintain stability. Use the formula $V_{OUT} = V_{REF} \times (1 + \frac{R2}{R1}) + I_{ADJ}R2$ to calculate the resistor values.

Datasheet Reference:

• Download LM338 (LM138/LM338 Series) Datasheet

Commonly Used in:

• Bench Power Supplies: The flexibility and high current make it ideal for variable laboratory power supplies.
• Battery Charging Systems: Used to create constant voltage/constant current (CV/CC) battery chargers for lead-acid or lithium batteries.
• High-Power LED Drivers: Engineers employ it in current-regulated circuits for driving high-power LED arrays.

Applications:

• Local On-Card Regulation: Providing efficient, localized voltage control on large circuit boards to power specific subsystems.
• High-Current Logic Supplies: Powering large digital systems, like FPGA boards or industrial controllers, that draw significant current.
• Adjustable Constant Current Sources: Easily configured as a current source for testing, charging, or driving various loads.

Equivalent Models:

• LM317: While the LM317 is functionally similar, however, it is limited to 1.5A output current, making the LM338 the appropriate choice for high-power applications.
• LT1084 / LT1085 (Linear Tech): Functionally equivalent 5A and 3A adjustable low-dropout (LDO) regulators, often used as substitutes for the LM338.
• LM1084-5.0 (Fixed): A fixed 5V, 5A version of the 1084 series, which can serve as an alternative when adjustable output is not required.

Package Includes:

• 1 x LM338 5A Adjustable Positive Voltage Regulator TO-220