Overview
The LM338K STEEL is an adjustable 3-terminal positive voltage regulator produced by Texas Instruments, originally developed by National Semiconductor. This regulator is capable of supplying up to 5 A of output current over a wide output voltage range of 1.2 V to 32 V. It is housed in a steel TO-3 metal package, which provides excellent thermal performance and durability. The LM338K STEEL is exceptionally easy to use, requiring only two external resistors to set the desired output voltage. It features outstanding load and line regulation, making it suitable for various power supply applications.
Key Specifications
| Parameter | Value | Unit |
|---|---|---|
| Output Voltage Range | 1.2 to 32 | V |
| Output Current | Up to 5 | A |
| Input-Output Voltage Differential | Up to 40 | V |
| Operating Junction Temperature | 0 to 125 | °C |
| Storage Temperature Range | -65 to 150 | °C |
| Lead Temperature (Soldering, 10 seconds) | 300 | °C |
| Dropout Voltage | 2.7 | V |
| Line Regulation | 0.005% | |
| Load Regulation | 0.1% |
Key Features
- Adjustable Output Voltage: The LM338K STEEL allows for adjustable output voltage using two external resistors.
- High Output Current: Capable of delivering up to 5 A of output current.
- Thermal Overload Protection: Includes thermal overload protection and safe operating area protection for the power transistor.
- Time-Dependent Current Limiting: Allows peak currents of up to 12 A for short periods, reducing to a safe value under sustained loading conditions.
- Low Output Impedance: NPN Darlington output topology provides naturally low output impedance.
- High Ripple Rejection: Bypassing the adjustment pin can achieve very high ripple-rejection ratios.
Applications
- Power Supplies: Ideal for power supply circuits requiring adjustable output voltage.
- Battery Charging: Used in battery charging systems to regulate charging voltage.
- LED Drivers: Suitable for driving LEDs with regulated voltage and current.
- Constant Current Regulators: Can function as a precision current regulator by connecting a fixed resistor between the ADJUST and OUTPUT terminals.
Q & A
- What is the LM338K STEEL?
The LM338K STEEL is a 5-amp adjustable voltage regulator designed by Texas Instruments, capable of delivering output voltages from 1.2 V to 32 V.
- How does the LM338K STEEL work?
The LM338K STEEL operates as a linear voltage regulator, using a variable resistor to set the desired output voltage and adjusting the pass transistor to maintain the output voltage despite varying input voltages and load currents.
- How many pins does the LM338K STEEL have and what are their functions?
The LM338K STEEL has 3 pins: VIN (input voltage), ADJ (adjustable output), and VOUT (regulated output voltage).
- What are the pros and cons of the LM338K STEEL?
Pros include high output current, adjustable output, thermal regulation, and simple circuitry. Cons include the need for heat sinks in high power applications and a relatively high dropout voltage.
- Are there any equivalents or alternatives to the LM338K STEEL?
Alternatives include the LM317 from Texas Instruments, the LT1083 from Analog Devices, and the L200 from STMicroelectronics.
- What is the typical line and load regulation of the LM338K STEEL?
The typical line regulation is 0.005%, and the typical load regulation is 0.1%.
- What is the maximum input-output voltage differential for the LM338K STEEL?
The maximum input-output voltage differential is up to 40 V.
- What is the operating junction temperature range for the LM338K STEEL?
The operating junction temperature range is from 0°C to 125°C.
- Does the LM338K STEEL require any external capacitors for operation?
Normally, no capacitors are needed unless the device is situated more than 6 inches from the input filter capacitors, in which case an input bypass capacitor is recommended. An output capacitor can be added to improve transient response.
- How does the LM338K STEEL protect against overcurrent and overtemperature?
The LM338K STEEL includes time-dependent current limiting and thermal overload protection to protect the device against overcurrent and overtemperature conditions.
