STMicroelectronics SRK2001A

Overview

SRK2001A from STMicroelectronics is a secondary-side adaptive synchronous rectification controller optimized for LLC resonant converters with center-tapped secondary windings. It drives two N-channel MOSFETs independently, features dual Kelvin drain-source sensing (up to 90 V), adaptive turn-on masking (up to 10% of clock cycle), and adaptive two-slope turn-off logic-enabling zero-current switching without external parasitic inductance compensation. Used in high-efficiency 80+/85+ ATX and 90+/92+ server SMPS.

For engineers reviewing the SRK2001A datasheet, SRK2001A pinout, SRK2001A application, or SRK2001A equivalent, key selection criteria include its 4.5–32 V VCC range, 50 μA quiescent current in low-consumption mode, 500 kHz max operating frequency, SSOP10 package compatibility, and dual independent gate drive outputs with 11 V clamped high-level voltage.

Technical Context

The SRK2001A implements asynchronous digital state machines for interlocked dual-gate control, eliminating simultaneous conduction risk. Its core operation relies on precise Kelvin-sensed DVS-SVS differential inputs (with 100 Ω series resistors) to detect body diode conduction onset (VTH_ON = −100 mV) and zero-crossing, enabling cycle-by-cycle adaptive timing.

Turn-off uses two complementary mechanisms: a primary adaptive algorithm that maximizes conduction time by dynamically adjusting delay to target ≤75 ns body diode residual conduction, and a secondary ZCD_OFF comparator with self-adaptive threshold and 300 ns blanking-activated only during fast transients or above-resonance events to prevent current inversion and half-bridge failure.

Key Specifications

Pinout & Package

SSOP10 package (4.9 mm × 6.0 mm, 0.65 mm pitch), thermally enhanced with exposed pad connected to GND for improved thermal resistance (R_{th j-case} = 10 °C/W).

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC24612-2 and MP6908A, the SRK2001A uniquely combines dual independent adaptive turn-off, 90 V DVS tolerance, and ZCD_OFF transient protection-making it the only option qualified for 92+ server SMPS with stringent reliability and efficiency requirements across full load range.

Availability

SRK2001A is available at Aetrix Electronics and suitable for AC-DC adapters, high-end flat panel TV power supplies, and 90+/92+ compliant server SMPS requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SRK2001A 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, Switzerland, specializing in power management, analog, and microcontroller solutions for industrial, automotive, and consumer markets.

The SRK2001A belongs to ST's high-efficiency power conversion controller family, designed specifically to maximize LLC resonant converter efficiency through intelligent secondary-side synchronous rectification without external compensation.

FAQ

What is the purpose of the 100 Ω resistor required on DVS1 and DVS2 pins?

The 100 Ω resistor limits dynamic current injection into the DVS input comparators during fast dV/dt events caused by transformer leakage inductance or MOSFET switching noise. Without it, excessive current could damage internal ESD protection structures or cause false triggering. ST specifies this value based on characterization across temperature and process corners, and it is mandatory per DS11726 Section 7.1.

How does the PROG pin determine burst-mode exit duty-cycle?

The PROG pin connects to an internal 10 μA current source. The resulting voltage (V_PROG) selects one of four predefined duty-cycle values (0%, 65%, 75%, or 80%) from an on-chip lookup table during VCC ramp-up. Resistor values are defined in Table 4 of DS11726 Rev 5: e.g., 180 kΩ yields 65%, open-circuit yields 0%. Configuration is latched and retained as long as VCC remains within 4.5–32 V and EN > 0.45 V.

Why does SRK2001A use Kelvin sensing instead of single-ended drain sensing?

Kelvin sensing (separate DVS and SVS pins per channel) rejects common-mode noise and eliminates voltage drop errors from PCB trace resistance and MOSFET source inductance. This ensures accurate detection of true drain-to-source voltage across R_DS(on), critical for reliable zero-current turn-off in high-frequency LLC converters where stray inductance can cause premature switching. Single-ended sensing would misread the actual V_DS due to source inductance voltage drop.

Can SRK2001A operate without a VCC supply once started?

No. The datasheet explicitly prohibits floating VCC after startup (Section 7). While the IC can be powered from the LLC output rail, VCC must remain within 4.5–32 V at all times during operation-even if DVS1/DVS2 are active. Disconnection or undervoltage of VCC during switching risks uncontrolled gate drive behavior and potential device damage due to dV/dt-induced currents on DVS pins.