LM2991S Negative Voltage Regulator

Overview

The LM2991S is a high-performance, low-dropout (LDO) adjustable negative voltage regulator designed to deliver a stable output voltage ranging from −3V to −24V. Capable of supplying up to 1A of load current, this regulator is engineered for applications requiring precise voltage regulation with minimal power dissipation. The device incorporates advanced circuit design techniques to achieve low dropout voltage, low quiescent current, and excellent temperature stability, making it suitable for a wide range of industrial, automotive, and consumer electronics applications.

One of the standout features of the LM2991S is its integrated On/Off pin, which allows for remote shutdown capability. This functionality is particularly useful in power-sensitive designs where power sequencing or energy efficiency is critical. The regulator's robust design ensures reliable operation under varying load and temperature conditions.

Features

• Adjustable Output Voltage: Configurable from −3V to −24V, providing flexibility for diverse applications.
• High Output Current: Supports up to 1A of continuous load current.
• Low Dropout Voltage: Optimized for minimal voltage drop across the regulator, enhancing efficiency.
• Remote Shutdown Capability: Features an On/Off pin for enabling or disabling the regulator remotely.
• Low Quiescent Current: Designed for power-sensitive applications, minimizing idle power consumption.
• Precision Reference: Incorporates a low-temperature-coefficient reference for stable performance across temperature variations.
• Thermal Protection: Built-in safeguards to prevent damage from overheating.
• Short-Circuit Protection: Enhanced reliability with protection against output short circuits.

Applications

The LM2991S is versatile and finds use in a broad spectrum of applications, including but not limited to:

• Industrial Power Supplies: Used in systems requiring stable negative voltage rails for analog and digital circuits.
• Automotive Electronics: Suitable for infotainment systems, sensors, and other automotive modules requiring regulated negative voltages.
• Consumer Electronics: Ideal for audio amplifiers, display drivers, and other portable devices.
• Telecommunications: Provides reliable voltage regulation in networking equipment and communication devices.
• Test and Measurement Equipment: Ensures precision voltage references for accurate measurements.

Electrical Characteristics

The following table summarizes the key electrical specifications of the LM2991S under typical operating conditions (unless otherwise noted):

Absolute Maximum Ratings

• Input Voltage (V_IN): −30V
• Output Voltage (V_OUT): −3V to −24V
• Output Current (I_OUT): 1A (continuous)
• Operating Junction Temperature: −40°C to +125°C
• Storage Temperature: −65°C to +150°C

Typical Performance Characteristics

• Dropout Voltage: 0.6V (typical) at 1A load current
• Line Regulation: 0.02%/V (typical)
• Load Regulation: 0.1% (typical)
• Quiescent Current: 10mA (typical)
• Reference Voltage Tolerance: ±2% (over temperature range)

Functional Description

The LM2991S operates by comparing the feedback voltage (derived from the output) with an internal precision reference. The error amplifier adjusts the pass transistor to maintain the desired output voltage. The On/Off pin, when pulled to a logic low, disables the regulator, reducing the quiescent current to a minimal level. This feature is particularly useful for power management in battery-operated devices.

Package Information

The LM2991S is available in a robust TO-263 (D2PAK) surface-mount package, which offers excellent thermal performance and mechanical durability. The package is designed for high-power applications, with a low thermal resistance to facilitate efficient heat dissipation.

Package Dimensions (TO-263)

• Length: 10.16mm (max)
• Width: 8.89mm (max)
• Height: 4.83mm (max)
• Lead Pitch: 2.54mm

Thermal Characteristics

• Thermal Resistance (Junction-to-Case): 3°C/W
• Thermal Resistance (Junction-to-Ambient): 50°C/W (with PCB heat sinking)

Conclusion

The LM2991S is a highly reliable and efficient negative voltage regulator, offering adjustable output, high current capability, and advanced protection features. Its low dropout voltage and remote shutdown functionality make it an excellent choice for modern electronic systems where power efficiency and reliability are paramount. Whether used in industrial, automotive, or consumer applications, the LM2991S delivers consistent performance under demanding conditions.