STMicroelectronics L6571A

Overview

L6571A from STMicroelectronics is a high-voltage half-bridge gate driver IC with integrated oscillator, designed to drive external N-channel MOSFETs and IGBTs in offline AC-DC and DC-DC converters. It features 600 V high-side floating supply capability, 1.25 μs internal dead time (typ.), 15.6 V Zener clamp on VS, 270 mA sink / 170 mA source output drive strength, and programmable oscillator frequency via external R-C network.

For engineers reviewing the L6571A datasheet, L6571A pinout, L6571A application, or L6571A equivalent, key selection considerations include dV/dt immunity (±50 V/ns), undervoltage lockout with hysteresis (1 V), bootstrap-based high-side operation, and DIP-8/SO-8 package compatibility for flyback, resonant, and half-bridge SMPS designs.

Technical Context

The L6571A integrates a self-oscillating timing circuit whose frequency is set by external RF and CF components (e.g., 12 kΩ + 1 nF yields ~60 kHz), and supports external logic drive via the CF pin. Its internal logic enforces fixed dead time to prevent shoot-through during complementary switching of high- and low-side power devices.

It operates with a floating high-side supply referenced to OUT (up to 618 V BOOT voltage), uses BCD off-line technology for robust HV integration, and includes ESD protection (900 V HBM on pins 6–8) and thermal shutdown safeguards. The VS pin incorporates a 15.6 V Zener clamp to limit supply rail overvoltage.

Key Specifications

Pinout & Package

Available in DIP-8 and SO-8 packages per ECOPACK® environmental compliance. Pinout defined per STMicroelectronics Doc ID 4946 Rev 6 (Figure 2, Table 4).

Key Features

Applications

Equivalent & Alternatives

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

Compared with IR2153 and UCC3732X, the L6571A uniquely combines programmable oscillator, built-in Zener clamp, and guaranteed 1.25 μs dead time-making it optimal for cost-sensitive, self-contained half-bridge SMPS where layout simplicity and robustness are critical.

Availability

L6571A is available at Aetrix Electronics and suitable for AC-DC adapters, LED drivers, industrial SMPS, and appliance power supplies requiring stable component supply and long-lifecycle support.

Supply support for L6571A 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, MCU, and automotive-grade silicon.

The L6571A belongs to ST's high-voltage AC-DC controller family, engineered specifically for cost-effective, self-oscillating half-bridge topologies in offline power conversion systems.

FAQ

What is the maximum recommended operating frequency for the L6571A?

The L6571A supports oscillator frequencies up to 200 kHz per datasheet Section 1.3. At 60 kHz (typical with 12 kΩ/1 nF), it delivers optimal gate drive strength and thermal performance. Operation above 100 kHz increases switching losses and requires careful PCB layout to maintain dV/dt immunity.

Can the L6571A drive IGBTs directly?

Yes-the L6571A's 270 mA sink and 170 mA source capability, combined with ±50 V/ns dV/dt immunity, is validated for driving standard 15–30 A IGBTs in half-bridge configurations. Gate resistor selection must ensure <1.25 μs turn-off delay to respect internal dead time constraints.

How does the VS pin Zener clamp function in practice?

The internal 15.6 V Zener on VS limits voltage to protect internal bias circuitry. It is not a regulator: connecting VS to a low-impedance >15.6 V source causes excessive current flow and thermal stress. A resistive dropper or auxiliary winding must supply VS within 10–15 V nominal range.

Is the L6571A pin-compatible with the L6571B?

Yes-L6571A and L6571B share identical pinout, package options (DIP-8/SO-8), and functional architecture. The sole difference is internal dead time: 1.25 μs (A) vs. 0.72 μs (B). Substitution requires verification that reduced dead time does not cause shoot-through in the target power stage.