STMicroelectronics L6565DTR

Overview

L6565DTR from STMicroelectronics is a current-mode quasi-resonant (QR) zero-voltage-switching (ZVS) flyback controller IC for offline AC-DC power supplies, featuring 1% precision internal 2.5 V reference, ±400 mA totem-pole gate driver, ultra-low start-up current (<70 µA), line voltage feedforward for constant power delivery, and frequency foldback for standby efficiency. It targets TV/monitor SMPS, AC-DC adapters, and digital consumer power supplies.

For engineers reviewing the L6565DTR datasheet, L6565DTR pinout, L6565DTR application, or L6565DTR equivalent, key selection criteria include ZCD-triggered QR timing accuracy, VFF-based adaptive overcurrent setpoint scaling, hiccup-mode OCP response to secondary short circuits, and UVLO-controlled gate driver pull-down behavior during undervoltage conditions.

Technical Context

The L6565DTR implements a transformer demagnetization-sensing ZCD input (pin 5) with arming threshold (2.1 V) and triggering threshold (1.6 V), blanked for ≥3.5 µs after MOSFET turn-off to enable reliable QR operation and frequency foldback. Its line feedforward (pin 3) scales the current-sense clamp voltage (VCSX) from 1.4 V at 0 V VFF down to 0.2 V at 3 V VFF, enabling constant power across 88–264 Vac input.

It integrates a 2.5 V ±1% bandgap reference referenced to INV (pin 1), error amplifier with 60–80 dB gain and 1 MHz GBW, and a dual-level OCP: pulse-by-pulse shutdown at VCS > 2.0 V and hiccup-mode recovery after VCC discharge below UVLO (9.5 V typ.). The totem-pole GD output (pin 7) delivers ±400 mA peak with built-in UVLO pull-down.

Key Specifications

Pinout & Package

SO-8 package (RoHS-compliant, surface-mount, 150 °C/W junction-to-ambient thermal resistance).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar quasi-resonant flyback controller applications.

Compared with ICE2QS03G and UCC28600DR, the L6565DTR offers superior line feedforward precision and ZCD arming logic for stable QR operation across universal mains, making it optimal for high-reliability TV and office equipment where constant power and EMI control are critical.

Availability

L6565DTR is available at Aetrix Electronics and suitable for TV/monitor SMPS, AC-DC adapters, and digital consumer power supplies requiring stable component supply, long-term lifecycle support, and RoHS-compliant SO-8 packaging.

Supply support for L6565DTR 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, designing and manufacturing analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L6565DTR belongs to ST's legacy AC-DC controller product line, engineered specifically for quasi-resonant flyback topologies in energy-efficient offline power supplies targeting Blue Angel and Energy Star compliance.

FAQ

What is the purpose of the VFF (pin 3) on the L6565DTR?

The VFF pin implements line voltage feedforward by scaling the current-sense comparator's clamp voltage (VCSX) inversely with input voltage. With a resistor divider from bulk DC to VFF, it reduces the overcurrent threshold from 1.4 V at low line to 0.2 V at high line, ensuring constant output power across 88–264 Vac input-critical for universal-input adapters meeting Energy Star requirements.

How does the ZCD pin (pin 5) support both QR operation and device disable?

Pin 5 serves dual functions: as a zero-current detector, it triggers MOSFET turn-on on a negative-going edge after first being armed by a positive edge >2.1 V; as a disable input, pulling it below 150 mV forces shutdown with reduced quiescent current. This dual use eliminates need for separate control pins, simplifying PCB layout while maintaining noise immunity via blanking and arming thresholds.

What is the significance of the 3.5 µs minimum blanking time on the ZCD pin?

The 3.5 µs blanking window after GD turn-off prevents false triggering from leakage inductance ringing and enforces frequency foldback. When required off-time falls below this value, the IC skips ringing cycles-reducing switching frequency in discrete steps-to maintain ZVS operation and minimize light-load losses, directly enabling Blue Angel compliance in TV and printer SMPS.

Does the L6565DTR support primary-side regulation without an optocoupler?

Yes-the L6565DTR supports primary-side regulation using the auxiliary winding voltage fed to the INV pin (pin 1), referenced to its internal 2.5 V ±1% bandgap. This eliminates the optocoupler and TL431, reducing cost and improving reliability in applications like 50 W TV SMPS, as validated in ST's Application Note AN2021 (Fig. 24).