LM2586T ADJ - Adjustable Switching Regulator

Overview

The LM2586T ADJ is a monolithic integrated circuit from the LM2586 series, specifically engineered for high-efficiency switching regulator applications. This adjustable version provides designers with flexibility in setting the output voltage to meet specific system requirements. The device is optimized for flyback, step-up (boost), and forward converter topologies, making it suitable for a wide range of power supply designs.

With its integrated architecture, the LM2586T ADJ simplifies power supply design while delivering robust performance. The regulator operates at a fixed frequency of 150 kHz, which provides a good balance between efficiency and component size. The current-mode control architecture ensures excellent line and load regulation characteristics.

Features

• Adjustable output voltage from 1.23V to 60V
• 150 kHz fixed frequency internal oscillator
• Current-mode control architecture
• Integrated soft-start function (typically 10 ms)
• Cycle-by-cycle current limiting
• External shutdown capability
• ±4% output voltage tolerance
• Wide input voltage range: 4V to 40V
• Up to 3A output switch current
• Thermal shutdown protection
• Available in TO-220-5 package

Applications

The LM2586T ADJ is versatile enough for numerous power conversion applications:

• DC-DC boost converters
• Flyback converters
• Forward converters
• Industrial power supplies
• Automotive power systems
• Telecommunications equipment
• Battery charging circuits
• LED driver circuits
• Distributed power systems

Electrical Characteristics

Absolute Maximum Ratings

• Input Voltage: -0.3V to +45V
• Output Switch Voltage: -0.3V to +65V
• Shutdown Pin Voltage: -0.3V to +25V
• Feedback Pin Voltage: -0.3V to +25V
• Operating Junction Temperature: +150°C
• Storage Temperature Range: -65°C to +150°C

Recommended Operating Conditions

• Input Voltage Range: 4V to 40V
• Output Voltage Range: 1.23V to 60V
• Operating Temperature Range: -40°C to +125°C
• Maximum Output Current: 3A (dependent on thermal conditions)

Typical Performance Characteristics

• Switching Frequency: 150 kHz ±10%
• Feedback Voltage: 1.23V ±2%
• Quiescent Current: 11 mA typical
• Shutdown Current: 50 µA typical
• Soft-start Time: 10 ms typical
• Current Limit Threshold: 3.3A typical
• Thermal Shutdown Threshold: 165°C typical

Package Information

TO-220-5 Package Details

The LM2586T ADJ is available in a 5-pin TO-220 package with the following pin configuration:

• Pin 1: Feedback (FB) - Connects to the voltage divider network for output voltage regulation
• Pin 2: Shutdown (SD) - Active high shutdown control (internal pull-down)
• Pin 3: Input (VIN) - Power supply input
• Pin 4: Ground (GND) - Circuit ground
• Pin 5: Output (SW) - Switch output to inductor

Mechanical Specifications

• Package Type: Through-hole mounted
• Number of Pins: 5
• Lead Material: Copper alloy
• Lead Finish: Matte Tin
• Package Dimensions: 10.16mm x 8.89mm x 4.45mm (LxWxH)
• Mounting Style: Vertical or horizontal
• Thermal Resistance (Junction-to-Ambient): 35°C/W
• Thermal Resistance (Junction-to-Case): 3°C/W

Design Considerations

Output Voltage Setting

The output voltage is set using an external resistor divider network connected between the output and the FB pin. The relationship is given by:

V_OUT = 1.23V × (1 + R1/R2)

Where R1 is the resistor from output to FB pin, and R2 is the resistor from FB pin to ground.

Inductor Selection

For optimal performance, select an inductor with:

• Current rating exceeding the maximum output current
• Low DC resistance to minimize power loss
• Saturation current at least 30% higher than peak switch current
• Recommended inductance range: 33 µH to 220 µH for most applications

Thermal Management

Proper heat sinking is essential when operating at high currents or high ambient temperatures:

• Use a thermal pad or heatsink for continuous operation above 1A
• Ensure adequate airflow in enclosed designs
• Monitor junction temperature to prevent thermal shutdown

Typical Application Circuit

A basic step-up (boost) converter configuration includes:

• Input capacitor (10 µF to 100 µF ceramic or electrolytic)
• Output capacitor (47 µF to 470 µF low-ESR type)
• Schottky diode (3A, 60V minimum)
• Inductor (selected per design requirements)
• Feedback resistor divider network
• Optional input filter for noise-sensitive applications