LM333K Adjustable Negative Voltage Regulator

Overview

The LM333K is a high-performance, adjustable 3-terminal negative voltage regulator designed to deliver in excess of −3.0A across a wide output voltage range of −1.2V to −32V. This component is engineered for ease of application, requiring minimal external components—only two resistors to set the output voltage and one output capacitor for frequency compensation. The LM333K is optimized for superior voltage regulation and low thermal transients, making it an ideal choice for demanding power supply applications.

With built-in protection features such as internal current limiting, thermal shutdown, and safe-area compensation, the LM333K ensures reliable operation under various load conditions. Its robust design makes it suitable for both industrial and commercial applications where stable and efficient negative voltage regulation is required.

Features

• High Output Current: Capable of supplying more than −3.0A.
• Adjustable Output Voltage: Output can be set from −1.2V to −32V using external resistors.
• Excellent Regulation: Optimized for tight voltage regulation under varying load conditions.
• Thermal Protection: Internal thermal shutdown prevents damage from overheating.
• Current Limiting: Built-in current limiting protects the regulator and load from excessive current.
• Safe-Area Compensation: Ensures reliable operation by preventing secondary breakdown.
• Minimal External Components: Requires only two resistors and one capacitor for operation.
• Low Thermal Transients: Designed to minimize thermal variations for stable performance.

Applications

The LM333K is versatile and can be used in a wide range of applications, including:

• Power Supplies: Negative voltage regulation in linear power supplies.
• Industrial Equipment: Reliable voltage regulation for industrial control systems.
• Audio Amplifiers: Negative rail voltage regulation in audio power amplifiers.
• Test and Measurement: Precision voltage sources for test equipment.
• Telecommunications: Stable negative voltage for communication devices.
• Automotive Electronics: Voltage regulation in automotive power systems.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM333K:

Absolute Maximum Ratings

• Input Voltage (V_IN): −35V
• Output Current (I_OUT): −3.0A (continuous)
• Power Dissipation (P_D): Internally limited
• Operating Temperature Range (T_J): 0°C to +125°C
• Storage Temperature Range (T_STG): −65°C to +150°C

Typical Performance Characteristics

• Line Regulation: 0.01%/V (typical)
• Load Regulation: 0.1% (typical)
• Output Voltage Range: −1.2V to −32V
• Dropout Voltage: 1.5V (typical at −3.0A)
• Ripple Rejection: 70dB (typical)

Package Information

The LM333K is available in a robust TO-3 metal can package, which provides excellent thermal performance and mechanical durability. The package dimensions and pin configuration are as follows:

TO-3 Package Dimensions

• Case Material: Metal Can
• Mounting Style: Through-hole
• Weight: Approximately 10 grams
• Pin Configuration:
  • Pin 1: Adjust
  • Pin 2: Output (V_OUT)
  • Pin 3: Input (V_IN)

Thermal Considerations

The TO-3 package is designed to efficiently dissipate heat, but proper heat sinking is recommended for high-current applications to ensure optimal performance and longevity. The thermal resistance from junction to case (θ_JC) is typically 4°C/W, and the thermal resistance from junction to ambient (θ_JA) is 35°C/W when mounted on an appropriate heat sink.

Conclusion

The LM333K is a highly reliable and efficient adjustable negative voltage regulator, offering exceptional performance for a wide range of applications. Its robust design, combined with advanced protection features, ensures stable operation under varying load and temperature conditions. Whether used in industrial power supplies, audio amplifiers, or telecommunications equipment, the LM333K delivers consistent and dependable voltage regulation.