STMicroelectronics L5993D

Overview

L5993D from STMicroelectronics is a primary-side constant-power PWM controller IC for offline and DC-DC flyback power supplies, featuring current-mode control, programmable duty cycle (0–100%), 1 A peak gate drive, internal 100 ns leading-edge blanking, and constant-power regulation vs. switching frequency up to 1 MHz. It operates in BCD60II technology and supports synchronization, soft-start, and hiccup-mode overcurrent protection.

For engineers reviewing the L5993D datasheet, L5993D pinout, L5993D application, or L5993D equivalent, key selection considerations include its constant-power function for CRT monitor SMPS, precise 5.0 V ±1.5% reference, UVLO with 5 V hysteresis, and dual-supply architecture (VCC for signal, VC for power stage).

Technical Context

The L5993D implements fixed-frequency current-mode PWM control with an integrated oscillator (RT/CT-based), error amplifier (2.5 V internal reference, 90 dB open-loop gain, 4 MHz GBW), and pulse-by-pulse current limiting triggered at 1.2 V on ISEN. Its constant-power function dynamically adjusts the current-limit threshold via SYNC-pin frequency-to-voltage conversion to maintain stable throughput across 31–64 kHz raster-scan frequencies.

It features fully latched PWM logic with double-pulse suppression, programmable soft-start (via external CSS), and independent supply rails: VCC (14–16 V startup, 9–11 V UVLO) powers control circuitry, while VC (up to 24 V) drives the external MOSFET through a 1 A capable totem-pole output with 13 V internal clamp and 100 ns blanking.

Key Specifications

Pinout & Package

Package: SO16N (16-pin small-outline integrated circuit, surface-mount, 1.27 mm pitch).

Key Features

Applications

Equivalent & Alternatives

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

Compared with UC3844B and TL494, the L5993D uniquely integrates constant-power regulation, 100 ns blanking, and SYNC-based frequency adaptation-critical for multisync monitor SMPS where power stability across varying line frequencies is mandatory.

Availability

L5993D is available at Aetrix Electronics and suitable for monitor SMPS power supplies, universal-input AC-DC adapters, industrial DC-DC converters, and flyback converters for CRT displays requiring stable component supply and long-term lifecycle support.

Supply support for L5993D 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 specializing in power management, analog, and microcontroller solutions for automotive, industrial, and consumer markets.

The L5993D belongs to ST's MultiPower BCD technology product line, designed specifically for high-voltage, high-current offline power supply controllers with integrated protection and adaptive regulation.

FAQ

What is the purpose of the C-POWER pin (pin 16) on the L5993D?

The C-POWER pin enables the constant-power function by connecting an external capacitor to SGND. This capacitor forms part of a frequency-to-voltage converter that scales the error amplifier's output (VCOMP) inversely with SYNC frequency-ensuring stable power delivery across varying raster scan rates (e.g., 31–64 kHz). If unused, pin 16 must be tied to VREF to disable the function.

How does the L5993D implement hiccup-mode overcurrent protection?

When ISEN voltage exceeds 1.2 V for longer than the minimum on-time allows, the L5993D triggers hiccup mode: it disables PWM, discharges the SS capacitor, and reinitiates soft-start after a delay. This cycle repeats continuously during fault conditions, limiting average power and preventing thermal runaway-unlike latched shutdown, it maintains system observability and automatic recovery.

Can the L5993D synchronize multiple controllers in a master-slave configuration?

Yes-the SYNC pin supports bidirectional synchronization. As master, it outputs 7 mA positive pulses on oscillator falling edges; as slave, it accepts 3.5 V logic-level sync pulses. When multiple L5993Ds operate in parallel, the fastest oscillator automatically becomes the master without external configuration-enabling seamless interleaving or redundancy in multi-rail systems.

What is the functional difference between VCC and VC pins?

VCC (pin 8) supplies only the signal circuitry (error amp, logic, references) and has UVLO (9–11 V) and 25 V Zener protection. VC (pin 9) supplies the high-current output stage (OUT driver) and can tolerate up to 24 V. Separating these rails prevents gate-drive transients from disturbing control-loop stability and allows independent decoupling-VC requires a local bulk capacitor to PGND, while VCC needs only a 0.1 µF film cap to SGND.