STMicroelectronics L6571BD

Overview

L6571BD 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 0.72 μs internal dead time (L6571B variant), 15.6 V Zener clamp on VS, 270 mA sink / 170 mA source output drive capability, and ±50 V/ns dV/dt immunity - enabling use in offline SMPS, CFL ballasts, and induction heating inverters.

For engineers reviewing the L6571BD datasheet, L6571BD pinout, L6571BD application, or L6571BD equivalent, key selection criteria include programmable oscillator frequency (via external R_F/C_F), bootstrap-based high-side floating supply operation, undervoltage lockout with hysteresis, low 150 μA startup current, and DIP-8/SO-8 package compatibility for industrial power stage designs.

Technical Context

The L6571BD implements a self-oscillating half-bridge controller with dual output drivers: a low-side driver referenced to GND (pin 5, LVG) and a high-side driver referenced to the floating OUT node (pin 7, HVG), supplied via BOOT (pin 8). Internal logic enforces fixed dead time (0.72 μs typ.) to prevent shoot-through during switching transitions.

Oscillation frequency is set externally via resistor RF (pin 2) and capacitor CF (pin 3), with thresholds of 8.0 V (upper) and 4.0 V (lower) on CF. The device accepts external logic drive on CF, allowing synchronous control or shutdown by pulling CF to GND - which forces low-side ON and high-side OFF.

Key Specifications

Pinout & Package

Package: SO-8 (small outline, 150 °C/W junction-to-ambient thermal resistance); RoHS-compliant ECOPACK® variant.

Key Features

Applications

Equivalent & Alternatives

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

Compared with IR21531PBF and UCC27201DR, the L6571BD uniquely integrates oscillator, Zener-clamped HV supply, and bootstrap-compatible high-side drive in a single SO-8 package - making it optimal for cost-sensitive, self-oscillating, 600 V-class offline half-bridge applications without external timing or level-shifting circuitry.

Availability

L6571BD is available at Aetrix Electronics and suitable for compact fluorescent lamp ballasts, induction heating inverters, and offline switch-mode power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant packaging.

Supply support for L6571BD 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, designing and manufacturing analog, MCU, power, and sensor solutions for industrial, automotive, and consumer markets.

The L6571BD belongs to ST's high-voltage analog power IC portfolio, developed specifically for cost-effective, self-contained half-bridge control in energy-efficient lighting and power conversion systems operating directly from rectified AC mains.

FAQ

What is the function of the CF pin beyond oscillator timing?

The CF pin serves dual roles: as the oscillator timing capacitor node and as a logic input for external control. Pulling CF to GND forces the low-side driver ON and high-side OFF - a hardware shutdown mode useful for fault recovery. This action must respect the 1 μs minimum discharge time to avoid latch-up, enforced by limiting discharge current with an RC network.

Can L6571BD drive IGBTs with gate charge >50 nC?

Yes - with appropriate external gate resistors. The L6571BD delivers 270 mA sink and 170 mA source into the gate, enabling ~20 ns rise/fall times into 1 nF loads. For IGBTs with Q_g >50 nC, use R_g = 10–22 Ω to limit peak current while maintaining safe dv/dt and ensuring full turn-on within 200 ns at 100 kHz switching.

How does the internal Zener clamp on VS affect system design?

The 15.6 V Zener clamp on pin 1 (VS) protects internal circuitry but prohibits direct connection to low-impedance DC sources above 15.6 V. System design must use a high-impedance resistive dropper or auxiliary winding with series diode to charge the VS decoupling capacitor - otherwise, excessive current will flow through the Zener, causing thermal overstress or failure.

Is L6571BD pin-compatible with L6571AD?

Yes - both share identical SO-8 pinout, electrical behavior, and functional block diagram. The only difference is internal dead time: L6571BD uses 0.72 μs (L6571B version), while L6571AD uses 1.25 μs (L6571A version). No layout change is needed when substituting; dead time selection depends on power device switching speed and required safety margin.