LM2990S-12 Technical Summary

LM2990S-12 Negative Voltage Regulator

Overview

The LM2990S-12 is a three-terminal, low-dropout (LDO) negative voltage regulator capable of delivering up to 1A of output current. Designed for applications requiring stable negative voltage rails, this regulator provides a fixed -12V output with high accuracy and excellent line/load regulation. Its low dropout voltage makes it particularly suitable for battery-powered systems and noise-sensitive analog circuits.

This component features internal current limiting, thermal shutdown protection, and reverse-battery protection, making it robust for demanding applications. The device operates over a wide temperature range and maintains regulation with very low quiescent current.

Key Features

Fixed -12V Output Voltage with ±5% accuracy over full operating range
High Current Capability: Up to 1A continuous output current
Low Dropout Voltage: Typically 0.6V at full load current
Excellent Line Regulation: 0.01%/V typical
Superb Load Regulation: 0.3% typical (0mA to 1A)
Built-in Protection:
- Current limiting for overload protection
- Thermal shutdown for overtemperature protection
- Reverse-battery protection
Wide Operating Temperature Range: -40°C to +125°C
Low Quiescent Current: 10mA typical
TO-263 (SMD) Package for efficient power dissipation

Applications

The LM2990S-12 is ideal for various applications requiring stable negative voltage supplies:

Industrial Control Systems: PLCs, motor controllers
Automotive Electronics: Infotainment systems, instrumentation
Test and Measurement Equipment: Oscilloscopes, signal generators
Telecommunications: RF circuits, base station equipment
Audio Equipment: Professional audio mixers, amplifiers
Medical Devices: Patient monitoring equipment
Battery-Powered Systems: Portable instruments, backup supplies

Electrical Characteristics

All specifications are for T_J = 25°C, V_IN = -13.6V, I_OUT = 500mA, unless otherwise noted.

Absolute Maximum Ratings

Input Voltage: -26V
Output Current: Internally limited
Power Dissipation: Internally limited
Operating Junction Temperature: -40°C to +125°C
Storage Temperature: -65°C to +150°C
Lead Temperature (Soldering, 10 sec): 300°C

Electrical Specifications

Output Voltage: -12V ±5% (-11.4V to -12.6V)
Line Regulation (V_IN = -13.6V to -25V): 10mV max (0.08%)
Load Regulation (I_OUT = 5mA to 1A): 36mV max (0.3%)
Dropout Voltage (I_OUT = 1A): 0.6V typical, 1V max
Quiescent Current: 10mA typical, 15mA max
Ripple Rejection (f = 120Hz): 60dB typical
Output Noise Voltage (10Hz to 100kHz): 100µV_RMS typical
Current Limit Threshold: 1.5A typical
Thermal Resistance, Junction-to-Case: 3°C/W

Package Information

The LM2990S-12 is available in a TO-263 (D²PAK) surface-mount package:

TO-263 Package Dimensions

Package Type: SMD (Surface Mount Device)
Terminal Count: 3
Body Size: 10.28mm x 9.65mm
Height: 4.57mm max
Lead Pitch: 2.54mm
Mounting Pad Layout:
- Input: 6.35mm x 6.35mm minimum
- Output: 6.35mm x 6.35mm minimum
- Ground: 6.35mm x 6.35mm minimum
Thermal Characteristics:
- Junction-to-Ambient Thermal Resistance: 35°C/W (with minimum pad layout)
- Junction-to-Case Thermal Resistance: 3°C/W

Typical Performance Characteristics

The LM2990S-12 exhibits excellent performance across various operating conditions:

Dropout Voltage vs. Load Current: Shows gradual increase from 0.1V at 100mA to 0.6V at 1A
Output Voltage vs. Input Voltage: Maintains regulation within 1% for input voltages from -12.6V to -25V
Output Voltage vs. Temperature: Variation of less than ±1% over full temperature range
Quiescent Current vs. Temperature: Remains stable between 9-11mA from -40°C to +125°C
Ripple Rejection vs. Frequency: Maintains >40dB rejection up to 100kHz

Design Considerations

Input Capacitor

A 10µF or larger tantalum or aluminum electrolytic capacitor should be connected between the input terminal and ground to ensure stability and improve transient response. The capacitor should be located as close as possible to the regulator.

Output Capacitor

While the LM2990S-12 is stable with just a 10µF output capacitor, using a larger value (22µF to 100µF) will improve transient response. Low-ESR capacitors are recommended for best performance.

Thermal Management

At full load current, the device may require heat sinking depending on ambient temperature and input voltage. The thermal resistance can be reduced by: