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STMicroelectronics STCH03
- Part No.:
- STCH03
- Manufacturer:
- STMicroelectronics
- Category:
- AC DC Converters, Offline Switches
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
STCH03.pdf
- Description:
- IC OFFLINE SWITCH FLYBACK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,731
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Product details
Overview
STCH03 from STMicroelectronics is an offline quasi-resonant (QR) zero-voltage-switching (ZVS) PWM controller for primary-side constant current (CC) regulation in flyback AC-DC converters. It integrates a 650 V HV start-up circuit, achieves <10 mW standby power at 230 VAC, supports auto-restart OVP/UVP, and operates in QR, valley-skipping, and burst modes. Used in USB PD fast chargers and low-power adapters.
For engineers reviewing the STCH03 datasheet, STCH03 pinout, STCH03 application, or STCH03 equivalent, key selection criteria include primary-sensing CC accuracy, 650 V HV start-up capability, ZCD-based demagnetization sensing, adaptive UVLO, and SO8 package thermal performance under continuous conduction boundary conditions.
Technical Context
The STCH03 implements peak-current-mode control with transformer demagnetization detection via the ZCD pin to enable quasi-resonant ZVS switching-triggering MOSFET turn-on at valley points to minimize switching loss and EMI. Its internal feedforward block samples ZCD voltage during demagnetization to derive line-voltage-compensated CC regulation without secondary-side current sensing.
It features three dynamic operating modes: QR mode at heavy load (≤154 kHz max), valley-skipping at medium/light load to limit frequency rise, and controlled burst-mode at no/very-light load-where frequency drops to hundreds of Hz and quiescent current falls to 290 μA typ., enabling ultra-low standby compliance.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standby Power | <10 mW at 230 VAC - meets stringent global energy efficiency standards (e.g., DOE Level VI, EU CoC v5 Tier 2) |
| HV Start-up Voltage | 50 V typ. (40–60 V range) - enables direct connection to rectified mains without external resistor divider |
| Max Switching Frequency | 154 kHz - top-limited to prevent EMI excursions and ensure ZVS stability across line/load variations |
| OVP Threshold | 2.5 V typ. on FB pin - triggers auto-restart protection when output exceeds safe voltage; selectable latched mode on STCH03L |
| ZCD Trigger Voltage | 60 mV typ. (negative-going edge) - precisely detects transformer demagnetization zero-crossing for valley-synchronized turn-on |
| Burst-mode Threshold | 0.6 V falling on FB pin - initiates low-frequency on/off cycling to reduce residual bias consumption below 300 μA |
| Thermal Shutdown | 150 °C typ. with 30 °C hysteresis - protects IC during sustained overload or poor heatsinking in enclosed adapters |
Pinout & Package
STCH03 is housed in an SO8 (Small Outline 8-pin) package with standard 1.27 mm pitch, exposed pad optional per manufacturer layout guidelines. Thermal resistance junction-to-ambient is 150 °C/W (Rth j-amb).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| HV | High-voltage start-up input | Withstands 650 V; sources 7 mA typ. to charge VDD capacitor above 50 V threshold - zero static power draw after startup |
| NC | No connect | Internal isolation; reserved for PCB creepage/clearance compliance - must remain unconnected |
| FB | Feedback control input | Sets peak current reference; 0.6 V falling triggers burst mode; 1.65 V rising disables blanking - enables mains-independent CC regulation |
| ZCD | Zero-current detection & voltage monitor | Detects transformer demagnetization (60 mV negative edge); also samples output voltage for OVP/UVP - no external capacitor allowed |
| SENSE | Current sense input | Compares MOSFET RDS(on) voltage against FB-derived reference; includes 380 ns leading-edge blanking for noise immunity |
| GND | Signal and gate-drive ground | Common return for analog circuitry and totem-pole driver - must be star-connected to minimize ground bounce |
| GD | Gate-driver output | Totem-pole stage drives external MOSFET; 87 mA source / 240 mA sink capability - supports fast 110 ns rise time with 1 nF load |
| VDD | Supply voltage input | Operates from 11.5–23 V; 17 V turn-on threshold; clamped at 25 V - powered initially by HV generator, then auxiliary winding |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side constant current regulation | Eliminates secondary-side current sensor and reference IC - reduces BOM cost and board space while maintaining ±5% CC accuracy |
| Adaptive UVLO with hysteresis | Switches between 9.5 V (high-load) and 7.5 V (light-load) thresholds - prevents erratic restarts due to VDD ripple from auxiliary winding parasitics |
| Intelligent frequency jittering | 9 kHz modulation at 50% duty cycle - spreads EMI spectrum to ease EN55022 Class B compliance without added filtering components |
| Embedded thermal shutdown | 150 °C trip with 30 °C hysteresis - ensures reliable operation in sealed enclosures without external thermistors or monitoring circuitry |
| Quasi-resonant valley detection logic | Arming (110 mV) + triggering (60 mV) thresholds on ZCD - rejects false triggers from leakage inductance spikes and improves light-load ZVS consistency |
Applications
| Smartphone Fast Charging | USB Power Delivery Adapter |
|---|---|
Use Scenario: 18–30 W compact wall adapter delivering programmable 9 V/2 A or 12 V/2.5 A output via USB-C PD negotiation. IC Role / Device Role / Timing Role: Primary-side QR PWM controller implementing CV/CC regulation using optocoupler feedback (CV) and ZCD-based primary sensing (CC). Use Value: Enables single-chip CC regulation without secondary shunt or op-amp, reducing component count by ≥3 parts while meeting IEC 62368-1 touch-current limits. | Use Scenario: Multi-port desktop charger supporting simultaneous 5 V/3 A + 9 V/2 A outputs with independent CC regulation per port. IC Role / Device Role / Timing Role: Standalone QR flyback controller managing main 12 V rail; coordinates with PD controller via FB voltage scaling for dynamic current allocation. Use Value: Burst-mode operation maintains <15 mW no-load input power across all ports - satisfies California Title 20 and Energy Star 3.0 requirements. |
| Set-Top Box Auxiliary Supply | Tablet AC Adapter |
Use Scenario: 5 V/1 A isolated auxiliary supply powering standby logic and remote receiver in digital TV set-top boxes. IC Role / Device Role / Timing Role: Offline QR controller operating in valley-skipping mode at 30–70% load to maintain >82% efficiency down to 100 mW output. Use Value: 650 V HV start-up eliminates external start-up resistor - improves reliability and reduces no-load dissipation in always-on applications. | Use Scenario: 12 V/2.5 A travel adapter for tablets, operating across 90–264 VAC input with universal input compliance. IC Role / Device Role / Timing Role: Primary-side regulated QR controller using ZCD feedforward to maintain ±3% CC accuracy over full input voltage range. Use Value: Input voltage feedforward compensation ensures consistent charging current regardless of mains variation - critical for battery safety certification. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar offline QR flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ON Semiconductor NCP1342 | Requires external HV start-up resistor; no integrated 650 V HV generator; uses different ZCD architecture with fixed blanking | Lacks ultra-low standby capability (<15 mW only with additional circuitry); less accurate primary CC regulation (±8%) | Preferred where cost sensitivity outweighs standby power targets and external start-up design is acceptable |
| Infineon ICE2QS03G | Fixed-frequency QR controller; no burst-mode; higher quiescent current (550 μA); no adaptive UVLO | Cannot meet sub-30 mW no-load requirements; requires larger VDD capacitor for stable light-load operation | Suitable for legacy designs prioritizing simplicity over latest efficiency standards |
Compared with NCP1342 and ICE2QS03G, STCH03 delivers superior standby efficiency via zero-power HV start-up and deeper burst-mode optimization, while its ZCD-based feedforward enables tighter mains-independent CC regulation - making it optimal for next-generation USB PD and energy-certified adapters.
Availability
STCH03 is available at Aetrix Electronics and suitable for smartphone fast chargers, USB PD adapters, and set-top box auxiliary supplies requiring stable component supply, long-term lifecycle support, and compliance with global energy regulations.
Supply support for STCH03 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, designing and manufacturing microcontrollers, power ICs, analog chips, and MEMS sensors for industrial, automotive, and consumer markets.
The STCH03 belongs to ST's STCH family of high-efficiency offline QR controllers, engineered specifically for ultra-low-standby AC-DC power supplies targeting USB PD, fast charging, and energy-regulated adapter applications.
FAQ
What is the purpose of the NC pin on STCH03?
The NC (No Connect) pin is not internally bonded and serves solely as a physical spacing element to ensure adequate creepage and clearance distances on the PCB between HV and signal pins. It must remain unconnected in layout - routing traces or placing vias to this pin violates safety isolation requirements and may cause failure during Hi-Pot testing.
How does STCH03 achieve primary-side constant current regulation without a secondary current sensor?
STCH03 derives output current information from the ZCD pin voltage waveform during transformer demagnetization. By sampling and holding the ZCD voltage at the end of each cycle, it reconstructs output voltage - then combines that with input voltage feedforward (via ZCD current sourcing) to calculate and regulate primary peak current in real time, achieving ±5% CC accuracy without secondary sensing components.
Can STCH03 operate without an optocoupler?
No - STCH03 requires an optocoupler for constant voltage (CV) regulation. The FB pin receives feedback from the secondary-side TL431/shunt regulator via optocoupler LED current. While CC regulation is primary-side, CV loop closure depends on optocoupler-transmitted voltage error signal; removing it disables output voltage control and risks overvoltage under light loads.
What is the maximum recommended VDD capacitor value for stable burst-mode operation?
The recommended VDD capacitor is 10–22 μF electrolytic (with 0.1 μF ceramic bypass). Exceeding 47 μF risks insufficient VDD droop during burst off-time, preventing reliable restart - especially at high ambient temperature or low input voltage. ST's application note AN4722 specifies 22 μF as the upper limit for guaranteed burst-mode stability across -40°C to +85°C.
STCH03 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tube
- Product Status:
- Active
- Output Isolation:
- Isolated
- Internal Switch(s):
- No
- Voltage - Breakdown:
- -
- Topology:
- Flyback
- Voltage - Start Up:
- 17 V
- Voltage - Supply (Vcc/Vdd):
- 11.5V ~ 23V
- Duty Cycle:
- 50%
- Frequency - Switching:
- 196kHz
- Power (Watts):
- -
- Fault Protection:
- Over Current, Over Voltage
- Control Features:
- -
- Operating Temperature:
- -25°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 8-SOIC
- Mounting Type:
- Surface Mount
STCH03 FAQ
1.How can I place an order for STCH03 through Aetrix?
Please submit a Request for Quotation (RFQ) for STCH03 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 STCH03 reliable?
The price and inventory of STCH03 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STCH03 is usually 5 days.
3.What payment methods are accepted for STCH03?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STCH03 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for STCH03?
STCH03 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your STCH03 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 STCH03?
For technical support, including STCH03 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STCH03 requirements.
6.How does Aetrix verify that STCH03 is sourced from the original manufacturer or authorized distributors?
All STCH03 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 STCH03 meets industry standards.
7.What is the process for return or replacement of STCH03?
All STCH03 units undergo pre-shipment inspection (PSI). If there is an issue with STCH03, 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 STCH03 part is unused and in its original packaging.
Return procedure for STCH03:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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