Texas Instruments SG3524N

Overview

SG3524N from STMicroelectronics is a monolithic fixed-frequency PWM controller IC for switching power supplies, featuring dual uncommitted transistor outputs, an internal 5 V ±1% reference, error amplifier, programmable oscillator (up to 300 kHz), pulse-steering flip-flop, and current-limit/shutdown circuitry. It supports single-ended or push-pull topologies in DC-DC converters, inverters, and polarity converters.

For engineers reviewing the SG3524N datasheet, SG3524N pinout, SG3524N application, or SG3524N equivalent, key selection considerations include oscillator timing component compatibility (RT/CT), output transistor saturation voltage (1–2 V at 50 mA), reference temperature stability (0.3–1% over 0–70°C), and standby current (8 mA typical at VIN = 40 V).

Technical Context

The SG3524N implements a fixed-frequency, voltage-mode PWM architecture where the error amplifier output compares against a linear ramp generated by the RT/CT-based oscillator. Its dual complementary outputs are steered via a synchronous flip-flop clocked by the oscillator, with built-in blanking to prevent shoot-through during transitions.

Internal circuitry includes a high-gain comparator (80 dB open-loop gain, 3 MHz bandwidth), current-sense input (200 mV threshold), and shutdown override capability via the error amplifier's common node - enabling external gain control or fault coordination in multi-regulator systems.

Key Specifications

Pinout & Package

SG3524N is supplied in a 16-pin plastic dual in-line package (DIP16) with 2.54 mm pitch, 20.0 × 8.5 mm body, and 3.3 mm max height. Pin 1 is marked by notch or dot; pin numbering follows standard DIP convention (counterclockwise from notch).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PWM controller applications.

Compared with UC3524N and TL494CN, the SG3524N offers superior oscillator flexibility (300 kHz max, CT-blanking), integrated reference stability (±1%), and lower standby current - making it optimal for space-constrained, thermally sensitive, or single-supply isolated converter designs.

Availability

SG3524N is available at Aetrix Electronics and suitable for flyback converters, push-pull DC-DC modules, voltage doublers, and polarity inverters requiring stable component supply across industrial, telecom, and instrumentation programs.

Supply support for SG3524N includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, specializing in power management, microcontrollers, and analog ICs for industrial, automotive, and consumer markets.

The SG3524N belongs to ST's legacy PWM controller product line, designed specifically for cost-effective, robust fixed-frequency switching regulator implementations in non-automotive industrial power systems.

FAQ

What is the maximum allowable voltage on the CT pin?

The CT pin sinks current and must not be driven above ground or below −0.3 V. Absolute maximum rating is −5 mA sink current. Exceeding this may damage the internal oscillator current source. Operation requires CT connected between Pin 4 and ground with RT from Pin 5 to VCC. External voltage sources or clamps on CT are prohibited.

Can SG3524N drive MOSFETs directly?

No - its NPN output transistors (Pins 11/12) are rated for 100 mA collector current and 2 V saturation voltage. They require external gate drivers or bipolar transistor buffers to safely switch power MOSFETs. Direct drive is limited to logic-level loads or low-current BJTs in auxiliary circuits.

How does the shutdown (DIS) pin interact with current limiting?

Pin 6 (DIS) is active-low and forces COMP low, overriding both error amplifier and current sense inputs. During shutdown, outputs are disabled and standby current drops to ~8 mA. Current limiting remains functional only when DIS is high (>2.5 V); it cannot trigger shutdown independently.

Is the VREF pin internally decoupled?

No - the VREF pin (Pin 10) has no internal bypass capacitor. A minimum 1 µF ceramic capacitor must be placed between Pin 10 and Pin 16 (VREF GND) to suppress noise and maintain regulation accuracy, especially under dynamic load conditions or when powering external circuitry.