STMicroelectronics L6590D

Overview

L6590D from STMicroelectronics is a monolithic off-line switching regulator IC with integrated 700 V lateral power MOSFET, designed for flyback, boost, and forward AC-DC converters operating from 88–264 V_AC mains. It delivers up to 15 W output power, features a 65 kHz (±10%) internal oscillator, 2.5 V ±2% internal reference, and standby mode reducing frequency to 22 kHz at light load.

For engineers reviewing the L6590D datasheet, L6590D pinout, L6590D application, or L6590D equivalent, key selection considerations include its integrated high-voltage start-up generator, brownout protection (SMD-only), cycle-by-cycle overcurrent limiting, latched overvoltage shutdown, and thermal shutdown with 40 °C hysteresis.

Technical Context

The L6590D implements voltage-mode PWM control using an internal error amplifier referenced to a 2.5 V ±2% bandgap, driving a fixed-frequency oscillator (65/22 kHz) and latch-based PWM comparator. Its SenseFET structure enables lossless current sensing for cycle-by-cycle OCP without external shunt resistors.

Brownout protection-exclusive to the SO16W package-is implemented via a dedicated BOK pin with 2.5 V threshold and programmable hysteresis via external resistor divider; thermal shutdown triggers at 150–165 °C with 40 °C hysteresis, and the internal 700 V MOSFET exhibits R_DS(on) = 13 Ω (typ.) at 25 °C.

Key Specifications

Pinout & Package

The L6590D is housed in a thermally enhanced SO16W (Wide SOIC-16) package with exposed thermal pad and internally bonded PGND pins (9–16) for efficient heat transfer to PCB copper. Ground pins are grouped to minimize thermal resistance (R_thj-pins = 20 °C/W).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar off-line flyback controller applications.

Compared with ICE2A0565Z and LNK304P, the L6590D uniquely combines 700 V integration, programmable brownout shutdown, and automatic 65↔22 kHz frequency scaling-enabling higher power density and compliance with strict European standby regulations in 10–15 W applications.

Availability

L6590D is available at Aetrix Electronics and suitable for wall plug adapters, monitor auxiliary supplies, desktop PC standby rails, and laser printer low-power modules requiring stable component supply and long-term industrial availability.

Supply support for L6590D 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 microcontroller solutions for industrial, automotive, and consumer markets.

The L6590D belongs to ST's legacy off-line AC-DC controller product line, engineered specifically for cost-optimized, high-efficiency flyback converters in sub-15 W universal-input power supplies.

FAQ

What is the purpose of the BOK pin on the L6590D?

The BOK (Brownout) pin is a dedicated input for mains undervoltage detection, available only on the SO16W package. It connects to a resistor divider across the bulk capacitor and disables PWM when voltage drops below 2.5 V. Its current-based hysteresis (±50 µA) allows independent setting of turn-on and turn-off thresholds, preventing oscillation near the trip point.

Can the L6590D operate with primary-side regulation only?

Yes. The L6590D supports primary-side regulation using its internal 2.5 V reference and high-gain error amplifier. VFB can be driven by a resistor divider from the auxiliary winding, eliminating the need for optocoupler and TL431. Compensation is applied via the COMP pin, and stability is ensured by the amplifier's 70 dB DC gain and 1 MHz unity-gain bandwidth.

How does the standby mode improve efficiency at light load?

At light load, peak primary current falls below 80 mA, triggering automatic reduction of oscillator frequency from 65 kHz to 22 kHz. This cuts switching losses-dominant at low output power-while maintaining regulation. When load increases and peak current exceeds 190 mA, frequency returns to 65 kHz, providing optimal heavy-load efficiency and transient response.

What thermal design guidance applies to the SO16W package?

The SO16W package uses pins 9–16 as PGND connections tied internally to the MOSFET source and thermal pad. For 1.5 W dissipation, ST recommends ≥3 cm² of 2 oz copper on the PCB layer beneath the package. Thermal resistance junction-to-ambient ranges from 40–65 °C/W depending on copper area and thickness-no external heatsink is needed with proper layout.