STMicroelectronics L6574

Overview

L6574 from STMicroelectronics is a high-voltage fluorescent lamp ballast controller IC designed for half-bridge resonant inverters driving CFL and TL lamps. It integrates preheat timing, frequency shifting, a current-controlled oscillator (f_PRE = 120 kHz typ., f_IGN = 60 kHz typ.), dual MOSFET gate drivers (250 mA source / 450 mA sink), and a dedicated op amp for closed-loop lamp current control - all operating up to 600 V rail voltage.

For engineers reviewing the L6574 datasheet, L6574 pinout, L6574 application, or L6574 equivalent, this page delivers verified functional context, validated SO16/DIP16 package mapping, confirmed preheat/frequency-shift timing behavior, real-world driver performance under 1 nF load (80/40 ns rise/fall), and accurate alternative part comparisons for lamp ballast design.

Technical Context

The L6574 implements a dual-stage timing architecture: CPRE capacitor controls preheat duration (t_PRE = K_PREF·C_PRE, K_PREF = 1.5 s/µF typ.) and subsequent frequency shift time (t_SH = 0.1·t_PRE). RPRE and RIGN set f_PRE and f_IGN independently, enabling precise ignition-to-burn transition.

Its integrated bootstrap section replaces external diodes using a synchronously driven HV DMOS, with internal clamping on VS (15.6 V typ.) and dV/dt immunity of ±50 V/ns across –40°C to +125°C ambient. The op amp (GBW = 1 MHz, V_IO = ±10 mV) feeds back to the RING pin for oscillator frequency modulation during closed-loop lamp regulation.

Key Specifications

Pinout & Package

Available in SO16 narrow (body width 3.9 mm) and DIP16 packages, both rated for 80°C/W (DIP16) and 120°C/W (SO16N) junction-to-ambient thermal resistance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar fluorescent lamp ballast controller applications.

Compared with IR21531 and UCC3895, the L6574 delivers fully integrated lamp ignition sequencing and closed-loop current regulation in a single chip - reducing system-level BOM, PCB area, and qualification effort for sub-60 W fluorescent ballasts.

Availability

L6574 is available at Aetrix Electronics and suitable for compact fluorescent lamp (CFL) ballasts, tubular fluorescent lamp (TL) ballasts, and dimmable fluorescent lighting systems requiring stable component supply and long-term lifecycle support.

Supply support for L6574 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, analog, and automotive ICs with vertical manufacturing capability and AEC-Q100 qualified processes.

The L6574 belongs to ST's AC-DC and lighting control product line, engineered specifically for energy-efficient electronic ballasts meeting IEC 60929, IEC 61000-3-2, and ENERGY STAR® lamp performance standards.

FAQ

What is the purpose of the CPRE pin and how does it affect lamp preheat?

The CPRE pin connects to an external capacitor that sets preheat duration (t_PRE = 1.5 s/µF × C_PRE) and frequency shift time (t_SH = 0.1 × t_PRE). During t_PRE, CPRE charges to 3.5 V at fixed current; then discharges and recharges at reduced rate to initiate frequency sweep from f_PRE to f_IGN, ensuring safe electrode heating before ignition.

Can the L6574 drive IGBTs instead of MOSFETs in the half-bridge?

Yes - the L6574's 450 mA sink / 250 mA source gate drivers and ±50 V/ns dV/dt immunity support standard 600 V IGBTs. However, due to higher gate charge and slower switching, rise/fall times exceed 80/40 ns with 1 nF load; external gate resistors must be adjusted to limit peak current and avoid shoot-through.

How does the integrated op amp enable closed-loop lamp current control?

The op amp (pins 5–7) compares sensed lamp current against a reference, then feeds its output through an RC-diode network to the RING pin. This modulates the oscillator's control voltage, dynamically adjusting f_IGN to maintain constant lamp power despite aging or line voltage variation - without requiring external PWM controllers.

What is the function of the EN1 and EN2 pins, and how do they differ in fault response?

EN1 (pin 8) forces latched shutdown on critical faults like lamp removal or overvoltage; recovery requires either power cycle or EN2 activation. EN2 (pin 9) restarts the full preheat-ignition sequence without power interruption - useful when initial ignition fails due to cold ambient or aged lamp electrodes.