National Instruments LM1085 Series manual LM1085 3A Low General Description, Features

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June 2005

LM1085

3A Low Dropout Positive Regulators

LM1085 3A Low

General Description

The LM1085 is a series of low dropout positive voltage regulators with a maximum dropout of 1.5V at 3A of load current. It has the same pin-out as National Semiconductor’s industry standard LM317.

The LM1085 is available in an adjustable version, which can set the output voltage with only two external resistors. It is also available in three fixed voltages: 3.3V, 5.0V and 12.0V. The fixed versions integrate the adjust resistors.

The LM1085 circuit includes a zener trimmed bandgap ref- erence, current limiting and thermal shutdown.

The LM1085 series is available in TO-220 and TO-263 pack- ages. Refer to the LM1084 for the 5A version, and the LM1086 for the 1.5A version.

Features

nAvailable in 3.3V, 5.0V, 12V and Adjustable Versions n Current Limiting and Thermal Protection

n Output Current

 

3A

n

Line Regulation

0.015%

(typical)

n

Load Regulation

0.1%

(typical)

Applications

nHigh Efficiency Linear Regulators n Battery Charger

n Post Regulation for Switching Supplies n Constant Current Regulator

n Microprocessor Supply

Dropout Positive

Connection Diagrams

TO-220

Application Circuit

10094702

Top View

TO-263

10094752

1.2V to 15V Adjustable Regulator

10094704

Top View

Basic Functional Diagram,

Adjustable Version

10094765

Regulators

© 2005 National Semiconductor Corporation

DS100947

www.national.com

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Contents Connection Diagrams FeaturesBasic Functional Diagram Adjustable Version LM1085 3A Low General DescriptionOrdering Information Simplified SchematicAbsolute Maximum Ratings Note Electrical CharacteristicsOperating Ratings Note 120 10.0Dropout Voltage vs. Output Current Typical Performance CharacteristicsRipple Rejection vs. Frequency LM1085-Adj Load Transient Response Ripple Rejection vs. Output Current LM1085-AdjApplication Note Basic Adjustable RegulatorProtection Diodes Power Dissipation Diagram Typical Applications Automatic Light control Battery Backup Regulated SupplyGenerating Negative Supply voltage Ripple Rejection EnhancementLM1085 LM1085 3A Low Dropout Positive Regulators

LM1085 Series specifications

The National Instruments LM1085 Series is a range of low-dropout (LDO) voltage regulators that are designed for various applications requiring precise voltage regulation and minimal power loss. This series is particularly known for its high efficiency and excellent thermal performance, making it suitable for both consumer electronics and industrial systems.

One of the standout features of the LM1085 series is its low dropout voltage, typically around 1.5V at maximum load. This characteristic allows these regulators to function effectively even with minimal headroom, which is essential for battery-powered applications. The series supports output voltages of 1.25V to 3.3V, enabling designers to tailor the voltage output to meet specific requirements, thereby enhancing system flexibility.

The LM1085 series incorporates several advanced technologies. It utilizes a high-speed, low-noise architecture, which contributes to stable operation across a variety of load conditions. Additionally, the regulators have built-in protection features, including thermal shutdown and current limiting, which prevent damage due to overheating or short-circuits.

Another characteristic that sets the LM1085 series apart is its ability to deliver a maximum output current of 3A, catering to applications with higher power requirements. This makes it an excellent choice for powering microcontrollers, sensors, and other digital circuitry that demand stable voltage levels.

The LM1085 series is also compatible with a range of external components, such as capacitors and inductors, allowing engineers to customize their designs based on specific requirements, including transient response and load variation. Furthermore, its low noise output makes it ideal for sensitive applications in audio processing and communication systems.

In summary, the National Instruments LM1085 Series stands out due to its low dropout voltage, high current capacity, integrated protection features, and compatibility with external components. Its efficient design makes it a preferred choice for applications where precise regulation and efficiency are paramount. Whether for consumer electronics, automotive, or industrial systems, the LM1085 series offers reliable performance that meets the needs of modern electronic designs.