STMicroelectronics L6590N

Overview

L6590N 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 delivering up to 15 W. It features a 65 kHz (±10%) internal oscillator, 2.5 V ±2% precision reference, cycle-by-cycle overcurrent protection, and standby mode reducing frequency to 22 kHz at light load.

For engineers reviewing the L6590N datasheet, L6590N pinout, L6590N application, or L6590N equivalent, key selection considerations include its integrated high-voltage start-up generator, non-dissipative biasing, thermal shutdown with hysteresis, brownout protection (SMD variant only), and compatibility with primary or secondary feedback topologies.

Technical Context

The L6590N implements voltage-mode PWM control using an internal error amplifier (70 dB DC gain, 1 MHz GBW) referenced to a trimmed 2.5 V bandgap. Its oscillator operates at 65 kHz (normal) or 22 kHz (standby), with duty cycle limited to 70% max and minimum 0%. The MOSFET features 13 Ω R_DS(on) @ 25°C and 700 V V_(BR)DSS, source-grounded for direct transformer primary connection.

Protections include latched overvoltage shutdown triggered at 16.5 V on V_CC, pulse-by-pulse current limiting (625 mA typ.), thermal shutdown at 150°C with 40°C hysteresis, and - in the SO16W variant - brownout detection via BOK pin with 2.5 V threshold and current-hysteresis sensing. The MINIDIP package lacks brownout functionality.

Key Specifications

Pinout & Package

The L6590N is supplied in a 16-pin MINIDIP package (dual-in-line, through-hole). Ground pins (6, 7, 8) are internally bonded to the metal frame for enhanced thermal dissipation; PCB copper area ≥3 cm² (2 oz) achieves R_thj-amb ≈ 35–60°C/W. High-voltage clearance is supported by N.C. pins adjacent to DRAIN.

Key Features

Applications

Equivalent & Alternatives

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

Compared with ICE2A280Z and UC3842BD1G, the L6590N uniquely integrates both 700 V MOSFET and non-dissipative start-up, enabling smaller footprints and lower no-load power - critical for Blue Angel and Energy Star Level VI certification in sub-15 W adapters.

Availability

L6590N is available at Aetrix Electronics and suitable for wall plug power supplies, AC-DC adapters, and auxiliary power supplies requiring stable component supply and long-term industrial availability.

Supply support for L6590N 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, specializing in power management, analog, and microcontroller solutions for industrial, automotive, and consumer markets.

The L6590N belongs to ST's legacy off-line AC-DC controller family, engineered specifically for cost-sensitive, high-efficiency <15 W flyback converters targeting energy-regulated consumer and computing peripherals.

FAQ

What is the maximum continuous output power achievable with the L6590N?

The L6590N is rated for up to 15 W output power in flyback configuration with adequate PCB copper area (≥3 cm², 2 oz) and proper heatsinking. At full load, junction temperature remains within 150°C limit when ambient is ≤50°C. Output power is constrained by R_DS(on) (13 Ω), thermal resistance (35–60°C/W), and peak current limit (625 mA).

Does the L6590N support primary-side regulation without an optocoupler?

Yes - the L6590N supports primary-side regulation using its V_FB pin and internal 2.5 V reference. By sampling reflected auxiliary winding voltage via a resistor divider into V_FB, closed-loop control is achieved without optocoupler or secondary-side shunt regulator, reducing cost and improving reliability in low-power adapters.

How does the standby mode reduce power consumption at light load?

Standby mode reduces switching frequency from 65 kHz to 22 kHz when peak drain current falls below 80 mA. This cuts switching losses - dominant at light load - by ~65%, lowering no-load input power to under 500 mW at 264 V_AC. Frequency resumes automatically at 190 mA peak current, ensuring seamless transition without audible noise or regulation loss.

Is brownout protection available on the L6590N (MINIDIP) package?

No - brownout protection is implemented only in the SO16W variant (L6590D). The L6590N MINIDIP package lacks the BOK pin and associated comparator circuitry. For brownout detection in MINIDIP designs, external circuitry (e.g., TL431-based undervoltage monitor) must be added to disable the controller via the COMP pin.