LM3524D - Precision Switchmode Pulse Width Modulation Control Circuit

Overview

The LM3524D represents an enhanced version of the industry-standard LM3524 pulse width modulation controller. This improved family maintains pin-for-pin compatibility with existing 3524 series components while offering superior specifications and additional features that reduce the need for external supporting circuitry. The device integrates all the control circuitry required for DC-to-DC converters or DC-to-AC inverters, making it particularly suitable for switchmode power supply applications.

Key improvements include a precision voltage reference, enhanced output drive capability, and extended voltage ranges for critical components. The LM3524D operates over a wide temperature range and provides excellent stability, making it suitable for demanding industrial and commercial applications.

Features

• Pin-for-pin compatible with standard LM3524 devices
• Precision 5V reference with ±1% accuracy
• Enhanced output drive capability (200mA sink/source current)
• Reduced output transistor saturation voltage (V_CEsat)
• Increased output transistor breakdown voltage (60V V_CE)
• Extended error amplifier common mode range (0V to 5.5V)
• Improved oscillator linearity and temperature stability
• Separate oscillator and control sections for flexible timing
• Adjustable deadtime control for output stages
• Undervoltage lockout protection
• Wide operating temperature range (-40°C to +125°C)

Applications

The LM3524D is designed for a wide range of power control applications, including:

• Switchmode power supplies (buck, boost, flyback, forward converters)
• DC-DC voltage converters
• DC-AC inverters
• Battery chargers
• Uninterruptible power supplies (UPS)
• Motor speed controllers
• Precision voltage regulators
• Solar power systems
• Industrial power control systems

Electrical Characteristics

Absolute Maximum Ratings

• Supply Voltage (V_CC): 40V
• Output Collector Voltage: 60V
• Output Emitter Voltage: -0.3V to +5V
• Output Current (sink or source): 200mA
• Reference Output Current: 50mA
• Error Amp Input Voltage Range: -0.3V to V_CC
• Operating Junction Temperature: -40°C to +125°C
• Storage Temperature Range: -65°C to +150°C

Recommended Operating Conditions

• Supply Voltage (V_CC): 8V to 40V
• Oscillator Frequency Range: 100Hz to 300kHz
• Timing Capacitance Range: 0.001µF to 0.1µF
• Timing Resistance Range: 1.8kΩ to 100kΩ
• Operating Ambient Temperature: -40°C to +85°C

Electrical Specifications (T_A = 25°C, V_CC = 20V unless otherwise noted)

• Reference Output Voltage: 4.95V to 5.05V (±1%)
• Reference Voltage Line Regulation: 10mV (V_CC = 8V to 40V)
• Reference Voltage Load Regulation: 20mV (I_REF = 0 to 20mA)
• Reference Voltage Temperature Stability: ±0.5mV/°C
• Oscillator Frequency Range: 100Hz to 300kHz
• Error Amp Input Offset Voltage: ±2mV
• Error Amp Input Bias Current: 0.5µA
• Error Amp Common Mode Rejection: 70dB
• Error Amp Open Loop Gain: 80dB
• Output Saturation Voltage: 1.2V (I_OUT = 100mA)
• Output Leakage Current: 100µA
• Current Limit Threshold: 200mV
• Supply Current: 15mA (no load)

Package Information

SOIC-16 Package (D Suffix)

• Package Type: 16-Lead Small Outline Integrated Circuit (SOIC)
• Package Dimensions: 9.90mm x 3.90mm body
• Lead Pitch: 1.27mm
• Lead Count: 16
• Mounting Style: Surface Mount
• JEDEC Standard: MS-012
• Operating Temperature Range: -40°C to +125°C
• Moisture Sensitivity Level (MSL): 1 (Unlimited Floor Life)
• RoHS Compliance: Yes

Pin Configuration

• Pin 1: Inverting Input (Error Amp)
• Pin 2: Non-Inverting Input (Error Amp)
• Pin 3: Oscillator Output/Sync Input
• Pin 4: Current Limit Input
• Pin 5: Current Sense Input
• Pin 6: Timing Capacitor
• Pin 7: Timing Resistor
• Pin 8: Ground
• Pin 9: Emitter Output 1
• Pin 10: Collector Output 1
• Pin 11: Collector Output 2
• Pin 12: Emitter Output 2
• Pin 13: V_CC (Supply Voltage)
• Pin 14: Reference Output (5V)
• Pin 15: Non-Inverting Input (Error Amp)
• Pin 16: Inverting Input (Error Amp)

Functional Description

The LM3524D integrates all the primary functions required for pulse width modulation control in a single IC. The device contains a precision voltage reference, error amplifier, programmable oscillator, pulse-steering flip-flop, two uncommitted output transistors, and current-limiting circuitry.

The error amplifier compares a portion of the output voltage with the precision reference to generate an error signal. This signal controls the pulse width of the output transistors through the pulse-width modulator. The oscillator frequency is set by an external resistor and capacitor, allowing flexibility in design. The deadtime control feature prevents simultaneous conduction of both output transistors.

The improved output stage features higher current capability and lower saturation voltages compared to standard versions, improving efficiency in power conversion applications. The extended common mode range of the error amplifier simplifies feedback network design in various topologies.