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STMicroelectronics STCH03TR
- Part No.:
- STCH03TR
- Manufacturer:
- STMicroelectronics
- Category:
- AC DC Converters, Offline Switches
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
STCH03TR.pdf
- Description:
- IC OFFLINE SWITCH FLYBACK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:4,440
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Product details
Overview
STCH03TR 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 STCH03TR datasheet, STCH03TR pinout, STCH03TR application, or STCH03TR equivalent, key selection criteria include its primary-sensing CC regulation accuracy, 650 V HV start-up capability, ZCD-based demagnetization sensing, and adaptive UVLO behavior under light-load bias fluctuations.
Technical Context
The STCH03TR implements peak-current-mode control with transformer demagnetization detection on the ZCD pin to enable quasi-resonant switching-triggering MOSFET turn-on at voltage valleys to minimize switching losses. Its internal feedforward block uses ZCD current sourcing to compensate for mains voltage variation, enabling line-independent CC regulation without secondary current sensing.
Burst-mode operation activates when FB voltage falls below 0.6 V (typ.), reducing switching frequency to ~few hundred Hz at no load; combined with zero-power HV start-up and 290 µA quiescent current, it meets stringent energy-efficiency standards. All protections-including OVP (selectable latched/auto-restart), UVP, OTP, and hiccup-mode OCP-are implemented with dedicated analog comparators and sampled-hold circuits on ZCD/FB/SENSE pins.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Standby Power | <10 mW at 230 VAC - enables compliance with EU CoC Tier 2 and DOE Level VI efficiency requirements. |
| Max Switching Frequency | 154 kHz - top-limited to prevent EMI excursions and ensure ZVS stability across line/load variations. |
| HV Start-up Voltage | 50 V (typ.) - initiates charging of VDD capacitor directly from rectified mains, eliminating external start-up resistor. |
| OVP Threshold | 2.5 V (typ.) on FB pin - triggers protection after 4 consecutive cycles; mode selectable (auto-restart or latched) via internal option. |
| ZCD Trigger Voltage | 60 mV (typ., negative-going edge) - detects transformer demagnetization zero-crossing for precise QR timing. |
| Burst-mode Threshold | 0.6 V (typ., falling) on FB pin - enters ultra-low-frequency on/off cycling to minimize residual losses at no load. |
| Thermal Shutdown | 150 °C (typ.) with 30 °C hysteresis - prevents thermal runaway during sustained overload or poor heatsinking. |
Pinout & Package
STCH03TR is housed in an SO8 package (8-pin, surface-mount, 150 °C/W junction-to-ambient thermal resistance), optimized for compact AC-DC adapter layouts with reinforced creepage/clearance spacing.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| HV | High-voltage start-up input | Withstands 650 V; sources 7 mA (typ.) to charge VDD capacitor until IC startup; zero-power idle state post-startup. |
| NC | No connect | Unbonded die pad; reserved for PCB safety clearance per IEC/UL creepage requirements. |
| FB | Feedback control input | Sets peak current threshold via optocoupler feedback; determines burst-mode entry (0.6 V), CV/CC transition, and adaptive UVLO exit (0.72 V). |
| ZCD | Zero-current detection & voltage monitor | Detects transformer demagnetization (60 mV trigger); provides line feedforward current; samples output voltage for OVP/UVP; ±3 mA sink/source limit. |
| SENSE | Primary current sense input | Compares MOSFET current against FB-derived reference; includes 380 ns leading-edge blanking for noise immunity; 0.75 V clamp limits overcurrent. |
| GND | Signal and gate-drive ground return | Single-point star ground required; separates pulsed power return from analog signal paths to avoid coupling noise into FB/ZCD. |
| GD | Gate-driver output | Totem-pole stage drives external MOSFET; 137 mA source / 240 mA sink drive strength; 110 ns rise time with 1 nF load. |
| VDD | Supply voltage input | Operates from 11.5–23 V; starts at 17 V (typ.), restarts at 4.5 V (falling); clamped to 26.5 V by internal Zener. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side constant current regulation | Eliminates secondary-side current sensor and reference IC while maintaining ±5% CC accuracy across universal input (85–265 VAC). |
| Quasi-resonant ZVS control | Reduces MOSFET turn-on loss and EMI by synchronizing switching to transformer valley points via ZCD sensing. |
| Adaptive UVLO | Adjusts VDD turn-off threshold based on FB voltage level to stabilize bias supply during light-load auxiliary winding dropout. |
| Intelligent frequency jittering | Modulates switching frequency at 9 kHz with 50% duty cycle to spread EMI energy and ease filter design. |
| Integrated thermal shutdown | Triggers at 150 °C with 30 °C hysteresis, ensuring safe recovery without external thermal monitoring components. |
Applications
| Smartphone Fast Charging Adapter | USB Power Delivery (PD) Auxiliary Supply |
|---|---|
Use Scenario: 18–30 W compact wall adapter delivering programmable 5/9/12/15/20 V output with tight CC/CV regulation. IC Role / Device Role / Timing Role: Primary-side QR PWM controller managing ZVS timing, CC regulation via ZCD feedforward, and burst-mode transitions at light load. Use Value: Enables <10 mW no-load consumption and >90% peak efficiency without optocoupler-based current feedback or external OVP circuitry. | Use Scenario: 5–10 W auxiliary power rail inside USB PD sink devices (e.g., monitors, docks) requiring stable 5 V/2 A output. IC Role / Device Role / Timing Role: Offline flyback controller providing isolated CV/CC output with integrated UVP to protect downstream PD controller during short-circuit events. Use Value: Delivers robust short-circuit immunity via UVP auto-restart and hiccup-mode OCP, eliminating need for external current-limiting FETs or timers. |
| Set-Top Box (STB) Standby Power Supply | Notebook PC Auxiliary Bias Supply |
Use Scenario: 3–5 W always-on auxiliary supply powering MCU, IR receiver, and network wake-up circuitry in STBs. IC Role / Device Role / Timing Role: Low-quiescent-current QR controller operating in burst mode at sub-100 mW load, with adaptive UVLO maintaining regulation during brownout conditions. Use Value: Achieves <30 mW total system standby power by combining zero-power HV start-up, 290 µA IQ, and controlled burst frequency scaling. | Use Scenario: 6–12 V/1 A isolated bias supply for notebook EC (Embedded Controller) and keyboard backlight drivers. IC Role / Device Role / Timing Role: Primary-sensing CC controller regulating output current during dynamic load steps (e.g., backlight ramp-up), using ZCD-based feedforward for line-invariant response. Use Value: Maintains ±3% current regulation across 90–264 VAC input without secondary shunt regulator, reducing BOM count and thermal stress. |
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 | Supports higher max frequency (200 kHz), lacks integrated 650 V HV start-up (requires external resistor), uses different ZCD architecture with fixed blanking. | Requires external HV start-up network and separate OVP circuit; better suited for designs needing tighter frequency control above 154 kHz. | Select when higher switching frequency or multi-mode digital control (e.g., DCM/QR/CCM hybrid) is prioritized over ultra-low standby power. |
| Infineon ICE2QS03G | Includes integrated 650 V start-up but uses fixed-frequency QR with no burst-mode; higher typical standby power (~25 mW). | No burst-mode operation - less effective for sub-50 mW no-load targets; simpler timing but lower light-load efficiency. | Select for cost-sensitive, non-regulatory-critical adapters where layout simplicity outweighs strict energy standard compliance. |
Compared with NCP1342 and ICE2QS03G, STCH03TR uniquely combines 650 V embedded start-up, primary-side CC regulation, and sub-10 mW standby - making it optimal for space-constrained, high-efficiency USB PD and smartphone charger designs where BOM reduction and regulatory pass margin are critical.
Availability
STCH03TR is available at Aetrix Electronics and suitable for smartphone fast chargers, USB PD auxiliary supplies, set-top box standby rails, and notebook PC bias supplies requiring stable component supply with full production lifecycle support.
Supply support for STCH03TR 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 STCH03TR belongs to ST's STCHx offline AC-DC controller family, engineered specifically for high-efficiency, low-standby-power QR flyback converters targeting USB-C PD, smartphone, and IoT power adapter applications.
FAQ
What is the purpose of the NC pin on STCH03TR?
The NC (No Connect) pin is internally unconnected and serves solely as a physical barrier on the SO8 package to increase creepage and clearance distance between HV and low-voltage pins. It must remain unconnected on the PCB to maintain reinforced insulation per IEC 60950-1 and UL 62368-1 safety standards - no routing, stitching, or grounding is permitted.
How does STCH03TR achieve primary-side constant current regulation without a secondary current sensor?
STCH03TR derives output current information indirectly via ZCD pin voltage sampling during transformer demagnetization. The ZCD current sourcing magnitude correlates with input voltage, allowing the internal CC loop to adjust peak current threshold dynamically - compensating for line variation and enabling accurate ±5% CC regulation using only primary-side components and optocoupler-based voltage feedback.
Can STCH03TR be used in continuous conduction mode (CCM) flyback designs?
No - STCH03TR is explicitly designed for discontinuous conduction mode (DCM) and boundary conduction mode (BCM) quasi-resonant operation. Its ZCD triggering logic, burst-mode thresholds, and frequency limiting are optimized for valley-switching in DCM/BCM. Attempting CCM operation results in loss of ZVS, increased EMI, and potential instability due to missing slope compensation and incorrect demagnetization detection.
What happens if the ZCD pin is accidentally AC-coupled or capacitively loaded?
Capacitive loading on the ZCD pin violates the datasheet requirement ("No capacitor is allowed") and disrupts demagnetization detection timing. It causes delayed or missed ZCD triggering, leading to hard-switching, excessive MOSFET stress, erratic burst-mode transitions, and potential failure to enter QR mode - resulting in elevated temperature, audible noise, and reduced efficiency. A direct DC-coupled connection to auxiliary winding is mandatory.
STCH03TR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- 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
STCH03TR FAQ
1.How can I place an order for STCH03TR through Aetrix?
Please submit a Request for Quotation (RFQ) for STCH03TR 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 STCH03TR reliable?
The price and inventory of STCH03TR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STCH03TR is usually 5 days.
3.What payment methods are accepted for STCH03TR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STCH03TR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for STCH03TR?
STCH03TR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your STCH03TR 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 STCH03TR?
For technical support, including STCH03TR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STCH03TR requirements.
6.How does Aetrix verify that STCH03TR is sourced from the original manufacturer or authorized distributors?
All STCH03TR 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 STCH03TR meets industry standards.
7.What is the process for return or replacement of STCH03TR?
All STCH03TR units undergo pre-shipment inspection (PSI). If there is an issue with STCH03TR, 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 STCH03TR part is unused and in its original packaging.
Return procedure for STCH03TR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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