STMicroelectronics SRK1000BTR

Overview

SRK1000BTR from STMicroelectronics is a secondary-side adaptive synchronous rectification controller for flyback converters, supporting QR and mixed CCM/DCM operation with programmable min TON and fixed 2.1–3.9 µs min TOFF. It features 100 V DVS sensing, 300 kHz max switching frequency, and 160 µA quiescent current in low-consumption mode-enabling high-efficiency USB PD profile 3 chargers and adapters.

For engineers reviewing the SRK1000BTR datasheet, SRK1000BTR pinout, SRK1000BTR application, or SRK1000BTR equivalent, key selection criteria include its adaptive ZCD turn-off logic, VAUX-assisted low-VCC operation, SOT23-6L package constraints, and TOFF_MIN differentiation versus SRK1000/SRK1000A for resonance immunity in QR flyback designs.

Technical Context

The SRK1000BTR implements dual-turn-off logic: adaptive ZCD_OFF comparator targeting 230–430 ns body-diode residual conduction time, plus 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 min TON from 0.28 µs to 3.9 µs, while TOFF_MIN is factory-fixed at 2.1–3.9 µs-optimized to exceed typical transformer ringing periods (TRES) in QR operation.

VAUX enables auxiliary supply takeover when VCC drops below 3.95 V, sustaining gate drive during CC regulation; DVS sensing uses ≥300 Ω series resistor for 100 V-rated drain monitoring; GD output delivers 0.6 A source / 1 A sink peak current with 11.6 V clamp and 45–140 ns rise/fall times into 4.7–10 nF loads.

Key Specifications

Pinout & Package

SOT23-6L package: 1.6 mm × 2.9 mm footprint, 1.1 mm height, thermal resistance Rth j-amb = 200 °C/W (with 10 mm² copper pour), suitable for space-constrained AC/DC board layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with SRK1000ATR and UCC24612-2QDR, SRK1000BTR provides superior resonance immunity via longer TOFF_MIN and unique VAUX-assisted operation below 3.5 V VCC-critical for USB PD 3.0 CC regulation and high-efficiency quick-charger designs.

Availability

SRK1000BTR is available at Aetrix Electronics and suitable for USB PD chargers, universal wall adapters, and industrial flyback SMPS requiring stable component supply, consistent SOT23-6L packaging, and guaranteed TOFF_MIN specification for QR resonance suppression.

Supply support for SRK1000BTR 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 automotive, industrial, and consumer markets.

The SRK series targets high-efficiency AC/DC flyback conversion, specifically addressing the need for adaptive synchronous rectification in USB PD, quick-charge, and energy-efficient adapter applications.

FAQ

What distinguishes SRK1000BTR from SRK1000 and SRK1000A?

SRK1000BTR has a factory-set TOFF_MIN of 2.1–3.9 µs, higher than SRK1000 (0.35–0.65 µs) and SRK1000A (1.4–2.6 µs). This extended blanking time ensures reliable suppression of transformer ringing in QR flyback topologies with longer resonance periods, preventing false turn-on events that degrade efficiency or cause instability.

How does the VAUX pin improve performance in constant-current regulation?

During CC regulation, output voltage drops-causing VCC to fall below 3.95 V. The VAUX pin activates an internal switch that recharges the VCC bypass capacitor from an auxiliary winding or DVS-derived rectifier, maintaining gate drive capability down to 2 V output and avoiding premature SR disablement that would increase conduction loss.

Can SRK1000BTR operate in fixed-frequency CCM flyback converters?

Yes-SRK1000BTR supports mixed CCM/DCM operation. When a 100 pF capacitor is placed on the TON pin, it enables FF CCM timer mode with 56 ns period-increase compensation. This allows robust SR timing even with frequency-modulated controllers, provided switching period change per cycle stays below 14 ns to prevent progressive turn-off anticipation.

What layout guidance applies to the DVS pin to ensure reliable sensing?

The DVS pin must connect to the SR MOSFET drain through a ≥300 Ω series resistor to limit dynamic current injection during ringing. PCB trace should be short and远离 high-dV/dt nodes; avoid routing near primary switch or transformer windings. Ground plane beneath DVS trace must be uninterrupted to minimize capacitive coupling noise affecting ZCD comparator accuracy.