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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > DC DC Switching Controllers

STMicroelectronics SRK1000

Name: SRK1000
Brand: STMicroelectronics
SKU: SRK1000
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: SRK1000

Manufacturer:: STMicroelectronics

Category:: DC DC Switching Controllers

Package:: SOT-23-6

Datasheet:: SRK1000.pdf

Description:: ADAPTIVE SYNCHRONOUS RATIFICATIO

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Product details

Overview

SRK1000 from STMicroelectronics is a secondary-side adaptive synchronous rectification controller for flyback converters, supporting QR and mixed CCM/DCM operation with 3.75–32 V_CC, 300 kHz max switching frequency, and 160 µA quiescent current in low-consumption mode. It drives N-channel MOSFETs in USB PD profile 3 chargers and fast adapters.

For engineers reviewing the SRK1000 datasheet, SRK1000 pinout, SRK1000 application, or SRK1000 equivalent, key selection criteria include adaptive ZCD-based turn-off logic, programmable T_ON blanking (0.28–3.9 µs), fixed T_{OFF_MIN} options (0.35/1.4/2.1 µs), 100 V DVS sensing capability, and SOT23-6L thermal performance (R_{th j-amb} = 200 °C/W).

Technical Context

The SRK1000 implements dual-turn-off logic: adaptive zero-current detection (ZCD_OFF) that dynamically adjusts threshold to maintain target body-diode conduction time (T_{diode_off} = 230–430 ns), and a selectable timer-based turn-off triggered by DVS rising edge with anticipation (T_{ant_timer} = 180–380 ns). Timer mode is selected via 100 pF capacitor on TON pin for fixed-frequency CCM/DCM, or omitted for QR/DCM.

Its gate driver delivers 0.6 A source / 1 A sink peak current with 45 ns rise time (V_CC = 20 V, C_GD = 4.7 nF) and clamps output at 10.6–12.6 V. Low-consumption mode activates when SR MOSFET conduction falls below T_{ON_sleep_in} (0.49–4.29 µs) or primary burst-mode interval exceeds 80–160 µs, reducing I_q to 160 µA.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CC Range	3.75–32 V - supports wide-input flyback designs including 5 V–24 V auxiliary rails and CC regulation down to 2 V output.
Max Switching Frequency	300 kHz - enables high-power-density adapter and charger designs without compromising control loop stability.
I_q (Low-Consumption Mode)	160 µA - minimizes no-load power loss in USB PD and quick-charge applications meeting CoC Tier 2 & DOE VI requirements.
DVS Sensing Voltage	−3 to +100 V - directly interfaces with SR MOSFET drain through ≥300 Ω series resistor, eliminating external level-shifting circuitry.
T_{ON_MIN} Programmability	0.28–3.9 µs via R_TON (33 kΩ–250 kΩ) - suppresses noise-induced false turn-off during body-diode conduction in high-dV/dt flyback topologies.
T_{OFF_MIN} Options	0.35 µs (SRK1000), 1.4 µs (SRK1000A), 2.1 µs (SRK1000B) - matches transformer resonance period (T_RES) to prevent false triggering during valley-skip ringing.
Gate Drive Clamp	10.6–12.6 V - protects N-MOSFET gate oxide while maintaining strong drive strength across full V_CC range.

Pinout & Package

SOT23-6L package: 1.6 mm × 2.9 mm footprint, 1.3 mm height, thermally enhanced with exposed pad (not electrically connected); suitable for high-density PCB layouts in compact USB PD adapters.

Pin/Terminal	Circuit Role	Design Meaning
1 V_CC	Supply input	Bypass capacitor required near pin; powers internal logic and gate driver; UVLO thresholds at 4.18–4.42 V (on), 3.3–3.7 V (off).
2 GND	Reference return	Return path for bias and gate-drive currents; must be routed close to SR MOSFET source to minimize ground bounce.
3 GD	Gate driver output	Totem-pole stage drives N-MOSFET gate directly; clamped at ~11.6 V to prevent overvoltage; 0.6 A source / 1 A sink capability.
4 T_ON	Blanking time programming	Internal 8 µA current source sets T_{ON_MIN} via R_TON; 100 pF capacitor selects FF CCM/DCM timer mode.
5 V_AUX	Auxiliary supply input	Enables V_CC recharge during CC regulation when V_CC drops below 3.75–4.15 V; accepts up to 100 V input.
6 DVS	Drain voltage sense	High-voltage input referenced to GND; senses SR MOSFET drain via ≥300 Ω resistor; used for ZCD detection and timing.

Key Features

Feature	Design Value
Adaptive ZCD turn-off	Maintains fixed body-diode residual conduction time (230–430 ns) regardless of R_DS(on) drift or load transients, eliminating current-inversion risk.
Programmable T_ON blanking	Adjusts minimum MOSFET on-time (0.28–3.9 µs) to reject post-turn-on ringing without sacrificing light-load efficiency.
VAUX-assisted V_CC recharge	Extends synchronous rectification into constant-current regulation phase by sourcing V_CC capacitor from auxiliary winding or DVS rectifier.
Two-mode timer selection	Hardware-configurable via TON pin capacitor: QR/DCM mode (no cap) or FF CCM/DCM mode (100 pF) - no firmware or external logic needed.
Low-consumption sleep entry/exit	Automatically enters 160 µA mode when conduction falls below T_{ON_sleep_in}; exits when conduction exceeds 1.2×T_{ON_MIN} + 300 ns, ensuring seamless load-step response.

Applications

USB PD Quick Charger

Universal AC-DC Adapter

Use Scenario: 65 W USB PD 3.0 charger delivering 20 V/3.25 A with CC/CV regulation across 90–264 V_AC.

IC Role / Device Role / Timing Role: Secondary-side SR controller synchronizing N-MOSFET turn-on with body-diode conduction start and turn-off with adaptive ZCD to maximize efficiency at 20 V output.

Use Value: Enables >94% efficiency at full load and <75 mW no-load consumption by combining low-I_q sleep mode with VAUX-assisted V_CC sustain during CC phase.

Use Scenario: Multi-output 12 V/5 V/3.3 V universal adapter for laptops and peripherals operating in mixed CCM/DCM across line/load variations.

IC Role / Device Role / Timing Role: Adaptive SR controller managing N-MOSFET switching in fixed-frequency flyback with automatic transition between ZCD and timer-based turn-off based on load conditions.

Use Value: Eliminates need for manual dead-time tuning; maintains >92% efficiency from 10% to 100% load via programmable T_ON and selectable T_{OFF_MIN} variants.

Smartphone Fast Charging

Industrial Flyback Power Supply

Use Scenario: 30 W GaN-based fast charger using QR flyback topology with valley-skip modulation and 5–12 V variable output.

IC Role / Device Role / Timing Role: SR controller implementing QR-optimized timer mode (no TON capacitor) to prevent false turn-off during transformer resonance, while adapting ZCD threshold for stable zero-current detection.

Use Value: Reduces thermal stress on SR MOSFET by minimizing body-diode conduction time to 230 ns, enabling smaller heatsink and higher power density.

Use Scenario: 24 V/2 A industrial flyback supplying PLC I/O modules with strict -40°C to +105°C ambient operation and EMI compliance.

IC Role / Device Role / Timing Role: Robust SR controller with 100 V DVS rating and -40°C to +150°C junction temperature range, driving 40 V N-MOSFETs in fixed-frequency CCM operation.

Use Value: Ensures reliable SR operation under wide temperature swings and high dv/dt noise via 300 Ω DVS series resistor and adaptive blanking, reducing system-level filtering cost.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MP6908A	Fixed 120 ns T_{ON_MIN}, no programmable blanking; 5 V–30 V V_CC; 120 kHz max frequency.	Limited to QR-only flyback; lacks VAUX support and adaptive ZCD - less suitable for CC regulation or mixed-mode operation.	Select MP6908A only for cost-sensitive QR-only adapters where T_ON noise immunity is not critical.
NCP4306	Fixed T_{OFF_MIN} = 0.5 µs; no T_ON programming; 3.3 V–30 V V_CC; 200 kHz max frequency.	No VAUX pin or adaptive ZCD; relies on comparator-based turn-off - vulnerable to R_DS(on) variation and load transients.	Choose NCP4306 for legacy fixed-frequency DCM designs where simplicity outweighs adaptive performance.

Compared with MP6908A and NCP4306, the SRK1000 provides programmable noise immunity, VAUX-assisted CC-phase operation, and adaptive ZCD for consistent zero-current switching across R_DS(on) spread and load steps - critical for USB PD 3.0 and GaN-based fast chargers.

Availability

SRK1000 is available at Aetrix Electronics and suitable for USB PD quick chargers, universal AC-DC adapters, and industrial flyback power supplies requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for SRK1000 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 SRK1000 belongs to ST's high-efficiency power conversion controller family, engineered specifically for secondary-side synchronous rectification in flyback converters targeting USB PD, fast charging, and energy-efficient AC-DC adapters.

FAQ

What is the purpose of the VAUX pin on the SRK1000?

The VAUX pin provides auxiliary power to recharge the V_CC bypass capacitor when the main V_CC supply drops below 3.75–4.15 V during constant-current regulation. It accepts up to 100 V input and connects to an auxiliary winding or DVS rectifier, enabling uninterrupted SR operation in USB PD and fast-charger applications where output voltage decreases under heavy load.

How does the SRK1000 differentiate between QR and fixed-frequency operation modes?

The SRK1000 detects operation mode via hardware configuration on the TON pin: absence of a 100 pF capacitor selects QR/DCM mode with demagnetization-time-based timer anticipation, while presence of the capacitor enables fixed-frequency CCM/DCM mode using estimated switching period. No software or external signal is required - mode selection is fully passive and deterministic.

Can the SRK1000 drive high-side N-MOSFETs in a flyback secondary?

No - the SRK1000 is designed exclusively for low-side N-MOSFET configurations where the MOSFET source connects to output ground. Its GD pin is a ground-referenced totem-pole driver with no floating supply or level-shifting capability. High-side drive would require isolated gate drivers or P-MOSFETs, which are incompatible with this controller's architecture and pinout.

What determines the correct SRK1000 variant (SRK1000 vs. SRK1000A vs. SRK1000B) for a given design?

Variants differ solely in fixed T_{OFF_MIN} values: 0.35 µs (SRK1000), 1.4 µs (SRK1000A), 2.1 µs (SRK1000B). Selection depends on measured transformer resonance period (T_RES) during valley-skip operation - the chosen variant's T_{OFF_MIN} must exceed T_RES to prevent false turn-off. This is verified experimentally using DVS waveform observation under worst-case line/load conditions.

SRK1000 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: SOT-23-6

Packaging:: Tape & Reel (TR)

Product Status:: Active

Output Type:: -

Function:: -

Output Configuration:: -

Topology:: -

Number of Outputs:: -

Output Phases:: -

Voltage - Supply (Vcc/Vdd):: -

Frequency - Switching:: -

Duty Cycle (Max):: -

Synchronous Rectifier:: -

Clock Sync:: -

Serial Interfaces:: -

Control Features:: -

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-6

SRK1000 FAQ

1.How can I place an order for SRK1000 through Aetrix?

Please submit a Request for Quotation (RFQ) for SRK1000 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for SRK1000 reliable?

The price and inventory of SRK1000 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for SRK1000 is usually 5 days.

3.What payment methods are accepted for SRK1000?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for SRK1000 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for SRK1000?

SRK1000 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your SRK1000 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for SRK1000?

For technical support, including SRK1000 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your SRK1000 requirements.

6.How does Aetrix verify that SRK1000 is sourced from the original manufacturer or authorized distributors?

All SRK1000 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that SRK1000 meets industry standards.

7.What is the process for return or replacement of SRK1000?

All SRK1000 units undergo pre-shipment inspection (PSI). If there is an issue with SRK1000, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The SRK1000 part is unused and in its original packaging.

Return procedure for SRK1000:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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