STMicroelectronics SRK1001

Overview

SRK1001 from STMicroelectronics is a secondary-side adaptive synchronous rectification controller for flyback converters, supporting QR and mixed CCM/DCM operation with 3.7–32 V VCC supply, 185 V DVS sensing capability, and programmable TON/TOFF blanking times. It drives N-channel MOSFETs in AC-DC adapters and USB PD profile 4 chargers.

For engineers reviewing the SRK1001 datasheet, SRK1001 pinout, SRK1001 application, or SRK1001 equivalent, key selection criteria include its adaptive turn-off logic for zero-current detection, low-quiescent 170 µA sleep mode, SO8 package layout compatibility, and VAUX-assisted operation during CC regulation at 2 V output.

Technical Context

The SRK1001 implements dual-turn-off mechanisms: adaptive ZCD-based turn-off targeting 300 ns body-diode residual conduction (Tdiode_off), and a timer-based turn-off with 180–325 ns anticipation (Tant_timer), selectable via 100 pF on TON pin for fixed-frequency CCM/DCM or QR modes. Its DVS input tolerates up to 185 V with ≥300 Ω series resistor.

Control logic integrates DIS/SYNC pin for forced turn-off or burst-mode synchronization, VAUX-assisted VCC recharge below 3.95 V, and gate drive clamping at 11.6 V with 0.6 A source / 1 A sink peak current. Adaptive drive enables above 7.4 V VCC and disables below 6.5 V.

Key Specifications

Pinout & Package

SRK1001 is housed in an SO8 package with exposed pad for thermal performance (Θ_{th j-amb} = 125 °C/W). Pin layout supports compact secondary-side placement adjacent to SR MOSFET with minimal trace inductance.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MP6908A and NCP4306, SRK1001 uniquely combines adaptive turn-off for consistent body-diode conduction control, VAUX-assisted operation down to 2 V output, and independent TON/TOFF programming-enabling higher efficiency across QR, CCM, and mixed-mode flybacks without MOSFET-specific recalibration.

Availability

SRK1001 is available at Aetrix Electronics and suitable for AC-DC adapters, USB PD profile 4 chargers, and industrial SMPS requiring stable component supply, long-term lifecycle support, and guaranteed SO8 second-source availability.

Supply support for SRK1001 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, MCU, power, and sensor solutions for automotive, industrial, and consumer markets.

The SRK series targets high-efficiency secondary-side synchronous rectification in flyback topologies, specifically engineered to replace Schottky diodes in USB PD, fast-charging, and energy-efficient AC-DC power supplies.

FAQ

What is the minimum output voltage at which SRK1001 maintains synchronous rectification?

SRK1001 sustains SR operation down to 2 V output via its VAUX-assisted VCC recharge function. When VCC drops below 3.95 V, the internal VAUX switch activates, drawing charge from an auxiliary winding or DVS-rectified node to maintain gate drive capability-critical for USB PD profile 4 constant-current phases.

How does SRK1001 handle parasitic inductance in the SR MOSFET source path?

SRK1001's adaptive turn-off algorithm dynamically adjusts the ZCD_OFF threshold to target a fixed 300 ns body-diode residual conduction time (Tdiode_off), inherently compensating for stray inductance (e.g., 2.5 nH package inductance) without requiring layout changes or MOSFET RDS_ON recalibration.

Can SRK1001 operate in both QR and fixed-frequency flyback topologies?

Yes-SRK1001 supports both modes via hardware configuration: omitting the 100 pF capacitor on TON pin enables QR/DCM operation with demagnetization-time-based timer, while adding it configures fixed-frequency CCM/DCM mode with period-averaged timer anticipation, all managed internally without firmware.

What is the purpose of the DIS/SYNC pin beyond disabling the controller?

DIS/SYNC serves dual roles: pulling high forces immediate SR MOSFET turn-off and initiates low-consumption mode after 4 cycles; when used as SYNC input (with no capacitor on TON), a positive edge triggers precise turn-off independent of ZCD, enabling tight timing control in systems with primary-side synchronization signals.