STMicroelectronics SRK1000ATR

Overview

SRK1000ATR from STMicroelectronics is a secondary-side adaptive synchronous rectification controller for flyback converters, supporting QR and mixed CCM/DCM operation with programmable minimum TON (1.4–2.0 µs), fixed TOFF_MIN of 2.0 µs, and 100 V drain-sense capability. It drives N-channel MOSFETs with 0.6 A source / 1.0 A sink peak gate current and enters low-consumption mode at light load to maintain efficiency in USB PD profile 3 chargers.

For engineers reviewing the SRK1000ATR datasheet, SRK1000ATR pinout, SRK1000ATR application, or SRK1000ATR equivalent, this device is selected for high-efficiency AC-DC adapters requiring precise adaptive turn-off timing, burst-mode-aware sleep entry, and robust noise-immune DVS sensing in compact SOT23-6L footprint.

Technical Context

The SRK1000ATR implements dual-turn-off logic: adaptive ZCD-based turn-off targeting 230–430 ns body-diode residual conduction time, and a timer-based turn-off with 180–380 ns anticipation referenced to DVS rising edge. Its TON pin accepts 33 kΩ–250 kΩ resistors to set blanking time, and its VAUX pin enables auxiliary supply hold-up during CC regulation when VCC drops below 3.95 V.

It features integrated high-voltage DVS sensing (−3 to 100 V), clamped 11.6 V gate drive output, and internal UVLO thresholds (VCC_On = 4.3 V typ., VCC_Off = 3.5 V typ.). The IC distinguishes QR vs. fixed-frequency operation via presence/absence of 100 pF capacitor on TON pin - no capacitor selects QR/DCM timer mode.

Key Specifications

Pinout & Package

SOT23-6L package: 6-pin surface-mount, 1.3 mm × 2.9 mm footprint, 1.45 mm height, thermal resistance R_{th j-amb} = 200 °C/W (with 10 mm² copper pad).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar secondary-side synchronous rectification controller applications.

Compared with SRK1000TR and SRK1000BTR, the SRK1000ATR provides balanced TOFF_MIN (2.0 µs) for mid-power QR and mixed-mode flybacks, offering optimal noise immunity without over-blanking - critical for 30–45 W USB PD adapters where resonance period typically falls between 1.2–2.4 µs.

Availability

SRK1000ATR is available at Aetrix Electronics and suitable for USB PD quick chargers, universal AC-DC adapters, and laptop power supplies requiring stable component supply with guaranteed long-term lifecycle support.

Supply support for SRK1000ATR 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 microcontrollers, power ICs, analog chips, and sensors for industrial, automotive, and consumer markets.

The SRK series targets high-efficiency AC-DC conversion, specifically optimizing secondary-side synchronous rectification in flyback topologies where adaptive timing, low-light-load consumption, and high-voltage sensing are essential.

FAQ

What is the purpose of the VAUX pin on SRK1000ATR?

The VAUX pin provides auxiliary supply hold-up during constant-current regulation when VCC drops below 3.95 V. It activates an internal switch to recharge the VCC bypass capacitor from an auxiliary winding or DVS-derived rectified voltage, ensuring uninterrupted SR operation down to 2 V output - critical for USB PD profile 3 compliance.

How does the SRK1000ATR differentiate QR and fixed-frequency operation modes?

It detects operation mode via presence or absence of a 100 pF capacitor on the TON pin: no capacitor selects QR/DCM timer mode (anticipation based on demagnetization time), while 100 pF enables fixed-frequency CCM/DCM mode (anticipation based on estimated switching period). This ensures optimal turn-off timing without external configuration pins.

Can SRK1000ATR drive high-side N-MOSFETs in active-clamp forward converters?

No - SRK1000ATR is designed exclusively for secondary-side synchronous rectification in flyback topologies. Its DVS sensing, adaptive ZCD logic, and gate drive architecture assume low-side SR MOSFET placement with source tied to output rail; it lacks high-side floating bias or level-shift capability required for active-clamp forward configurations.

What is the maximum recommended DVS series resistor value for noise immunity?

The datasheet specifies a minimum of 300 Ω but does not define a maximum. Practical design limits it to ≤1 kΩ: higher values increase RC filtering but degrade slew rate and delay DVS edge detection, risking missed turn-on events or inaccurate adaptive timing. For 100 V DVS transients, 470 Ω ±1% is commonly used with 0805 package for ESD robustness and layout stability.