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STMicroelectronics STCH03LTR
- Part No.:
- STCH03LTR
- Manufacturer:
- STMicroelectronics
- Category:
- AC DC Converters, Offline Switches
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
STCH03LTR.pdf
- Description:
- IC OFFLINE SWITCH FLYBACK 8SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:3,854
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Product details
Overview
STCH03LTR 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 STCH03LTR datasheet, STCH03LTR pinout, STCH03LTR application, or STCH03LTR equivalent, key selection criteria include primary-sensing CC accuracy, ZCD-based demagnetization detection timing, HV start-up leakage (<1 μA), adaptive UVLO hysteresis (30 °C), and SO8 thermal resistance (150 °C/W).
Technical Context
The STCH03LTR implements peak-current-mode control with transformer demagnetization sensing on the ZCD pin to enable QR operation-triggering MOSFET turn-on at valley points via negative-going edges below 60 mV after arming above 110 mV. Its internal feedforward path uses ZCD current sourcing (60–80 Ω equivalent) to compensate for mains variation in CC regulation.
Burst-mode activation occurs when FB voltage falls below 0.6 V (typ.), with hysteresis of 65 mV; during burst, VDD restart threshold drops to 3.2 V (falling), and quiescent current is 290–335 μA. Thermal shutdown activates at 150 °C (typ.) with 30 °C hysteresis, and leading-edge blanking on SENSE is fixed at 380 ns.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| HV Start Voltage | 50 V (typ.) - enables 650 V start-up cell only above bulk rectified input threshold, eliminating external bias winding during startup |
| Standby Power | <10 mW at 230 VAC - achieved via zero-power HV start-up (leakage <1 μA) and burst-mode operation down to ~300 Hz |
| Max Switching Frequency | 154 kHz - hard-limited top frequency ensures EMI compliance and prevents instability at light load/high line |
| OVP Threshold | 2.5 V (typ.) on FB pin - sampled-and-held ZCD voltage triggers latched or auto-restart protection depending on internal configuration |
| CC Regulation Accuracy | Primary-sensing only - eliminates optocoupler + secondary CC reference IC; mains-independent via ZCD feedforward (60–80 Ω RFF) |
| VDD Operating Range | 11.5–23 V - supports wide auxiliary winding design; UVLO thresholds differ by mode (9.5 V active, 7.5 V burst) |
| Thermal Shutdown | 150 °C (typ.) with 30 °C hysteresis - protects MOSFET gate driver and internal logic under sustained overload or poor heatsinking |
Pinout & Package
STCH03LTR is housed in an SO8 package (8-pin, surface-mount, 150 °C/W junction-to-ambient thermal resistance), compliant with JEDEC MS-012AC, with creepage/clearance optimized for 230 VAC offline applications.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| HV | 650 V high-voltage start-up input | Directly connects to rectified mains; sources 7 mA (typ.) to charge VDD until 17 V turn-on threshold is reached |
| NC | No-connect terminal | Unbonded die pad; reserved for PCB clearance to meet reinforced insulation requirements between primary and secondary sides |
| FB | Feedback control input | Sets peak current threshold (VCSx) and triggers burst mode when falling below 0.6 V; also controls adaptive UVLO exit (0.72 V rising) |
| ZCD | Zero-current detection & voltage monitor | Detects transformer demagnetization (negative edge <60 mV); provides line feedforward current (1 mA → 70 Ω) and samples output voltage for OVP/UVP |
| SENSE | Primary current sense input | Compares MOSFET current (via Rsense) against FB-derived reference; includes 380 ns blanking to reject switching noise |
| GND | Signal and power ground reference | Return path for all analog blocks and gate-driver sink current; must be isolated from noisy power return paths |
| GD | Gate-driver output | Totem-pole stage drives external MOSFET; 87 mA source / 240 mA sink (typ.); rise/fall times 110/40 ns with 1 nF load |
| VDD | Supply voltage input | Powered initially by HV start-up; sustained by auxiliary winding; clamped at 23–26.5 V; restarts at 4.5 V (falling) |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side constant current regulation | Eliminates secondary CC reference IC and shunt resistor; maintains ±5% current accuracy across 90–264 VAC input range via ZCD feedforward |
| Quasi-resonant valley detection | ZCD pin detects transformer demagnetization with 60 mV trigger threshold and 110 mV arming level, enabling ZVS turn-on and reducing EMI |
| Intelligent burst-mode control | Reduces switching frequency to ~300 Hz at no-load while maintaining regulated output; quiescent current drops to 290 μA (typ.) |
| Adaptive UVLO with dual thresholds | Switches between 9.5 V (active mode) and 7.5 V (burst mode) based on FB voltage, preventing erratic restarts during light-load transitions |
| Embedded 650 V HV start-up | Zero-power operation after startup (leakage <1 μA); self-limited charging current avoids external resistor sizing and improves reliability |
Applications
| Smartphone Fast Charging Adapters | USB Power Delivery (PD) Auxiliary Supplies |
|---|---|
|
Use Scenario: 18–30 W compact wall adapters delivering programmable 5/9/15 V outputs with tight CC/CV regulation. IC Role / Device Role / Timing Role: Primary-side QR controller managing MOSFET switching, ZCD-based valley detection, and FB-loop CC regulation without secondary feedback components. Use Value: Reduces BOM count by eliminating optocoupler + TL431 + CC reference IC; meets DOE VI/CoC Tier 2 <10 mW standby requirement. |
Use Scenario: Multi-rail auxiliary supplies in USB PD sink devices (e.g., monitors, docks) requiring stable 3.3 V/5 V rails from main converter output. IC Role / Device Role / Timing Role: Standalone flyback controller providing isolated, regulated auxiliary power with burst-mode efficiency at light load. Use Value: Enables >88% efficiency at 10% load via valley-skipping and burst-mode; thermal shutdown prevents failure during sustained no-load operation. |
| Set-Top Box (STB) Standby Power Supplies | Notebook AC Adapters (Low-Power) |
|
Use Scenario: 3–5 W always-on standby supplies powering remote IR receivers, network controllers, and real-time clocks in STBs. IC Role / Device Role / Timing Role: Offline QR controller operating in burst mode with <10 mW consumption; uses ZCD sampling for OVP/UVP without extra sensing circuitry. Use Value: Complies with EU ErP Lot 6 standby limits; integrated OVP auto-restart prevents latch-up during transient overvoltage events on mains input. |
Use Scenario: 20–45 W notebook adapters targeting compact form factor and high light-load efficiency for battery charging optimization. IC Role / Device Role / Timing Role: Primary-side CC/CV controller implementing QR + valley-skipping + burst-mode sequencing based on FB voltage and ZCD timing. Use Value: Achieves >85% efficiency at 10% load; soft-start (12–28 ms) prevents inrush current stress on input capacitor and rectifier. |
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 start-up cell; uses DCM+QR hybrid control instead of pure QR with ZCD triggering | Lacks primary-side CC regulation - mandates secondary-side current sensing and optocoupler feedback loop for CC | Choose when cost-sensitive designs allow external start-up and secondary feedback complexity; not suitable for ultra-low-standby (<15 mW) targets |
| Infineon ICE2QS03G | Fixed-frequency QR controller with internal start-up; no burst-mode capability; OVP is latched-only (no auto-restart option) | Higher standby power (~25 mW at 230 VAC); lacks adaptive UVLO and ZCD feedforward for mains-independent CC | Prefer for legacy designs where burst-mode noise sensitivity is critical; avoid when DOE VI/ErP compliance is mandatory |
Compared with NCP1342 and ICE2QS03G, STCH03LTR uniquely delivers integrated 650 V start-up, primary-side CC regulation, and multi-mode QR/burst operation - enabling single-chip, <10 mW standby solutions without secondary sensing or external HV components.
Availability
STCH03LTR is available at Aetrix Electronics and suitable for smartphone fast chargers, USB PD auxiliary supplies, STB standby power, and low-power notebook adapters requiring stable component supply, full traceability, and long-term lifecycle support.
Supply support for STCH03LTR 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, sensors, and analog products for industrial, automotive, and consumer markets.
The STCH03LTR belongs to ST's STCH family of offline QR controllers, engineered specifically for high-efficiency, ultra-low-standby AC-DC flyback converters in compact portable power applications.
FAQ
What is the function of the NC pin on STCH03LTR?
The NC (No Connect) pin is internally unconnected and serves solely as a physical barrier on the SO8 package to ensure adequate creepage and clearance distances between primary-side HV and secondary-side signal traces. It must remain unconnected on the PCB and is not used for thermal relief or grounding - violating this risks compromising reinforced insulation certification for 230 VAC applications.
How does STCH03LTR achieve primary-side constant current regulation without a secondary current sensor?
STCH03LTR derives output current information indirectly via the ZCD pin: during transformer demagnetization, the ZCD voltage waveform correlates with output voltage and turns ratio; combined with input voltage feedforward (via ZCD current sourcing), the controller calculates required peak primary current to maintain constant output current. This eliminates the need for a secondary shunt, op-amp, or dedicated CC reference IC.
Can STCH03LTR operate without an auxiliary winding?
No - STCH03LTR requires an auxiliary winding to sustain VDD after startup. The internal HV start-up circuit only charges VDD initially; once the converter begins switching, energy must be supplied continuously via the auxiliary winding. Without it, VDD collapses below 4.5 V, triggering restart cycles and preventing stable regulation.
What determines whether STCH03LTR uses auto-restart or latched OVP?
OVP behavior is fixed by part number: STCH03LTR is the tape-and-reel version of STCH03, which defaults to auto-restart OVP. The latched variant is STCH03L. No external configuration or pin strapping changes this - the protection mode is hard-coded in silicon and verified per device marking and ordering code in Table 1 of DS12460 Rev 2.
STCH03LTR Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- 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
STCH03LTR FAQ
1.How can I place an order for STCH03LTR through Aetrix?
Please submit a Request for Quotation (RFQ) for STCH03LTR 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 STCH03LTR reliable?
The price and inventory of STCH03LTR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STCH03LTR is usually 5 days.
3.What payment methods are accepted for STCH03LTR?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STCH03LTR transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for STCH03LTR?
STCH03LTR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your STCH03LTR 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 STCH03LTR?
For technical support, including STCH03LTR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STCH03LTR requirements.
6.How does Aetrix verify that STCH03LTR is sourced from the original manufacturer or authorized distributors?
All STCH03LTR 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 STCH03LTR meets industry standards.
7.What is the process for return or replacement of STCH03LTR?
All STCH03LTR units undergo pre-shipment inspection (PSI). If there is an issue with STCH03LTR, 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 STCH03LTR part is unused and in its original packaging.
Return procedure for STCH03LTR:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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