STMicroelectronics L6571AD

Overview

L6571AD from STMicroelectronics is a high-voltage half-bridge gate driver IC with integrated oscillator, designed to drive external N-channel MOSFETs and IGBTs in resonant and hard-switched topologies. It supports up to 600 V rail voltage, features 15.6 V internal Zener clamp on VS, 1.25 μs (L6571A) or 0.72 μs (L6571B) programmable dead time, ±50 V/ns dV/dt immunity, and operates across –40 °C to +125 °C ambient. Used in compact fluorescent lamp (CFL) ballasts and low-power AC-DC SMPS.

For engineers reviewing the L6571AD datasheet, L6571AD pinout, L6571AD application, or L6571AD equivalent, key selection criteria include bootstrap-based high-side drive capability, oscillator frequency programmability via external RC network, undervoltage lockout with hysteresis, sink/source current ratings (270 mA/170 mA), and DIP-8 or SO-8 package compatibility for layout-constrained lighting and adapter designs.

Technical Context

The L6571AD implements a self-oscillating half-bridge controller with internal logic enforcing non-overlapping gate drive signals and fixed dead time (1.25 μs typ. for L6571A variant). Its oscillator frequency is set by external RF and CF components and can be overridden by an external logic signal applied to the CF pin.

It uses BCD (Bipolar-CMOS-DMOS) off-line technology to integrate high-voltage level-shifting, gate drivers, protection circuitry, and timing functions on a single die. The VS pin includes a 15.6 V Zener clamp, and the BOOT/OUT floating supply supports up to 618 V, enabling direct high-side drive in bridge configurations without external charge pumps.

Key Specifications

Pinout & Package

Package: SO-8 (Small Outline, 150 mil width), RoHS-compliant ECOPACK® grade, thermal resistance R_thJA = 150 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar half-bridge gate driver applications.

Compared with IR21531PBF and BD6124FV, L6571AD offers balanced integration-retaining programmable frequency and internal VS clamp while supporting 600 V systems-making it optimal for mid-power CFL and adapter designs requiring reliability, low BOM count, and noise immunity.

Availability

L6571AD is available at Aetrix Electronics and suitable for compact fluorescent lamp (CFL) ballasts, low-power AC-DC adapters, and resonant DC-DC converters requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for L6571AD 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, delivering innovative silicon solutions for automotive, industrial, and power management applications.

L6571AD belongs to ST's high-voltage analog & power IC product line, engineered specifically for cost-effective, integrated half-bridge control in lighting and offline power conversion systems.

FAQ

What is the maximum allowable voltage on the BOOT pin?

The absolute maximum voltage on the BOOT pin is 618 V, as specified in Table 1 of the datasheet. This rating enables safe operation with 600 V rail systems when used with appropriate external bootstrap components (diode and capacitor rated ≥630 V). Exceeding this voltage risks permanent damage to the internal high-side driver stage.

Can the L6571AD drive IGBTs directly?

Yes-the L6571AD is explicitly designed to drive both N-channel MOSFETs and IGBTs. Its 270 mA sink and 170 mA source current ratings meet gate drive requirements for typical 20–50 A IGBTs used in CFL and low-power SMPS applications, provided gate resistors are selected to limit peak current within these limits.

How does the oscillator frequency change with temperature?

Figure 7 in the datasheet shows typical oscillator frequency variation of ±1.5% over –40 °C to +125 °C ambient. This stability is achieved through internal temperature-compensated current sources driving the external RC network, making it suitable for applications where moderate frequency drift is acceptable, such as lighting ballasts.

Is the L6571AD pin-compatible with the L6571A or L6571B?

Yes-L6571AD (SO-8) shares identical pinout and electrical functionality with L6571A (DIP-8) and L6571B (DIP-8/SO-8), differing only in package type and internal dead time (1.25 μs for L6571A/L6571AD, 0.72 μs for L6571B). No PCB redesign is needed when migrating from DIP-8 to SO-8 footprint.