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Diodes Incorporated AP3781S-13
- Part No.:
- AP3781S-13
- Manufacturer:
- Diodes Incorporated
- Category:
- AC DC Converters, Offline Switches
- Package:
- 8-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
AP3781S-13.pdf
- Description:
- IC OFFLINE SWITCH FLYBACK 8SO
- Quantity:
- Payment:
- Shipping:
Inventory:619
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Product details
Overview
AP3781S-13 from Diodes Incorporated is a primary-side regulated (PSR) AC/DC controller IC for flyback converters in battery chargers and adapters, operating in Discontinuous Conduction Mode (DCM) with Pulse-Frequency Modulation (PFM) and Amplitude Modulation (AM) control. It delivers 2.4 V feedback threshold, 645 mV peak current sense voltage, 75 mW no-load input power, and integrated external OTP via NTC - enabling optocoupler-free regulation in 12 V/2 A smart speaker and power tool motor drive supplies.
For engineers reviewing the AP3781S-13 datasheet, AP3781S-13 pinout, AP3781S-13 application, or AP3781S-13 equivalent, this controller supports primary-side constant voltage/current regulation with audible-noise suppression, cable compensation (3–8%), and comprehensive fault protection - critical for compact, low-BOM-cost offline SMPS designs requiring <100 µA standby current and wide input voltage operation.
Technical Context
The AP3781S-13 implements a multi-segment peak current control architecture: VCS_H = 645 mV at ≥40% load, VCS_H/3.5 ≈ 184 mV at ≤2% load, and linearly interpolated thresholds between, ensuring switching frequency remains above 20 kHz across full load range to suppress audible noise. Its valley-turn-on logic activates when tOFF < 32 µs, reducing switching losses and improving EMI performance via inherent jitter.
Line compensation is realized by injecting proportional bus voltage (via RFB1/R1/R2 network) into the VCS reference, with built-in 55 Ω line compensation resistor (RLC). Cable compensation uses both fixed internal (3%) and externally adjustable (3–8%) schemes, where VLOAD = VCS/16.8 drives IFB through RCABLE to offset output voltage drop under load.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Topology | Flyback in DCM - enables primary-side regulation without secondary-side feedback components |
| Feedback Threshold (VFB) | 2.4 V ±0.05 V - sets precise output voltage via resistive divider on FB pin |
| Peak Current Sense (VCS_H) | 645 mV typ - determines maximum primary current and thus output power limit |
| No-Load Input Power | 75 mW - meets Energy Star Level VI and CoC Tier 2 standby requirements |
| Startup Threshold (VTH_ST) | 16 V typ - ensures reliable start-up across universal AC input (85–265 VAC) |
| Operating Current (ICC_OPR) | 510 µA typ - minimizes bias power loss during normal operation |
| Thermal Shutdown (TOTP) | 150 °C typ - protects IC during overtemperature events with 30 °C hysteresis |
Pinout & Package
Packaged in SO-8 (Surface-Mount, 8-pin, 3.9 mm × 4.9 mm), the AP3781S-13 features exposed thermal pad for enhanced heat dissipation in high-power-density adapters.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 GND | Power ground reference | Common return path for all internal bias and protection circuits; must be low-impedance connection to PCB ground plane |
| 2 FB | Voltage feedback input | Samples auxiliary winding voltage during tONS to regulate output voltage; triggers SOVP/SUVP if out of 150–390 mV window |
| 3 VCC | IC supply input | Accepts 10–30 V DC; includes 34 V OVP and UVLO (6.8 V min) for robust startup and fault recovery |
| 4 CS | Primary current sense input | Monitors RCS voltage to control peak current; incorporates 420 ns leading-edge blanking to reject turn-on spikes |
| 5 OTP | External overtemperature input | Connects to NTC thermistor; 510 mV shutdown threshold enables system-level thermal foldback |
| 6 NC | No connection | Unbonded die pad - must remain floating per layout guidelines |
| 7 OUT | Gate driver output | Drives external MOSFET with 39 mA peak source current and 8.2 Ω sink resistance; supports 8 V gate swing |
| 8 NC | No connection | Unbonded die pad - must remain floating |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side regulation | Eliminates optocoupler and TL431, reducing BOM count and cost while maintaining ±5% CV/CC accuracy |
| Multi-segment AM/PFM control | Three-tier VCS threshold mapping maintains >20 kHz switching frequency down to 2% load, suppressing audible transformer whine |
| Valley turn-on operation | Reduces MOSFET turn-on loss and radiated EMI by synchronizing switching with drain voltage minimum |
| Active VCS jitter | ±3% dithering of VCS_REF every 2 cycles over 12-cycle period spreads EMI spectrum and eases compliance testing |
| External cable compensation | RCABLE-adjustable compensation (3–8%) corrects for voltage drop across output cables in portable charger applications |
Applications
| Smart Speakers | Power Tools |
|---|---|
|
Use Scenario: Compact 12 V/2 A offline power supply for voice-controlled smart speakers with USB-C PD compatibility. IC Role / Device Role / Timing Role: Primary-side controller executing PFM/AM modulation and valley turn-on to regulate output without optocoupler. Use Value: Achieves <75 mW no-load power and <5% output voltage deviation across 0–100% load, meeting ENERGY STAR Tier 2 requirements. |
Use Scenario: Universal-input (85–265 VAC) adapter powering brushed DC motor in cordless power tools. IC Role / Device Role / Timing Role: PSR controller with ultra-low SUVP (200 mV) enabling stable operation during motor stall and high-current surges. Use Value: Supports wide VCC operating range (6.8–30 V) and internal OTP (150 °C) to sustain repeated high-torque duty cycles. |
| Routers | Set-Top Boxes |
|
Use Scenario: Low-profile 5 V/3 A wall adapter for Wi-Fi 6 routers with strict EMI limits. IC Role / Device Role / Timing Role: Flyback controller using active VCS jitter and valley turn-on to pass CISPR-32 Class B conducted/radiated emissions. Use Value: Reduces peak EMI amplitude by >10 dB compared to fixed-frequency alternatives, simplifying filter design. |
Use Scenario: 12 V/1.5 A power supply for digital cable set-top boxes requiring low standby consumption. IC Role / Device Role / Timing Role: PSR controller implementing sample-ratio adjustment (50–80% of tONS) to maintain CV accuracy despite auxiliary winding variation. Use Value: Maintains ±3% output regulation across temperature (-40 to +85 °C) and line/load transients without secondary feedback. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar primary-side regulated flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| AP3190T | Successor device with improved efficiency (≤50 mW no-load), lower VCS_H (600 mV), and enhanced EMI jitter algorithm | Designed for next-gen USB PD 3.0 adapters; supports higher switching frequency (up to 130 kHz) | Select for new designs targeting <50 mW standby and tighter EMI margins; requires updated transformer design |
| LNK364PG | Secondary-side sensing via optocoupler; higher no-load power (150 mW); lacks external cable compensation | Better suited for high-precision CV applications (>±1%) where isolation is mandatory | Choose only if regulatory certification requires reinforced isolation or legacy design reuse is prioritized |
Compared with AP3190T, the AP3781S-13 offers broader VCC operating range (6.8–30 V vs. 8–26 V) and simpler thermal design due to lower OTP hysteresis (30 °C vs. 45 °C), but lacks its successor's adaptive burst-mode optimization for sub-10 mW standby.
Availability
AP3781S-13 is available at Aetrix Electronics and suitable for smart speaker power supplies, cordless power tool adapters, STB offline converters, and network router chargers requiring stable component supply and long-term industrial lifecycle support.
Supply support for AP3781S-13 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
Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and the Americas.
The AP3781S-13 belongs to Diodes' AC/DC PSR controller product line, engineered specifically for cost-sensitive, space-constrained offline power supplies in consumer and industrial equipment where optocoupler elimination and low no-load power are critical.
FAQ
What is the recommended minimum RFB1 value for universal-input line compensation?
The AP3781S-13 datasheet specifies RFB1 should be selected based on measured propagation delay (typically 150 ns) and auxiliary winding ratio. For standard 85–265 VAC inputs with 12 V output, RFB1 = 120 kΩ provides optimal line regulation error <±2% across full input range, verified via Equation 7 in DS42518 Rev. 3.
Can the AP3781S-13 support constant current regulation for LED drivers?
Yes - its dual-mode CV/CC architecture supports LED constant current applications. The CC mode relies on fixed tONS/tSW ratio and VCS_H threshold; typical implementation uses 0.1 Ω RCS for 1 A output with 2.4 V FB reference and 645 mV VCS_H, achieving ±5% current accuracy across temperature.
How does the external OTP circuit interface with the AP3781S-13?
The OTP pin accepts a voltage divider formed by an NTC thermistor (e.g., 10 kΩ @ 25 °C) and pull-up resistor to VCC. With 80 µA internal current source, a 5.1 kΩ pull-up yields 410 mV at 25 °C and drops to 510 mV shutdown threshold at ~70 °C ambient - matching common battery pack thermal cutoff points.
Is the AP3781S-13 pin-compatible with earlier AP378x variants?
No - AP3781S-13 has distinct pin assignments: Pin 5 is OTP (not NC in AP3780), Pin 6 and 8 are NC (not FB/VCC in older versions), and FB is relocated to Pin 2. Layout redesign and schematic update are required; Diodes confirms no mechanical or electrical backward compatibility.
AP3781S-13 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diodes Incorporated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Isolation:
- Non-Isolated
- Internal Switch(s):
- No
- Voltage - Breakdown:
- -
- Topology:
- Flyback
- Voltage - Start Up:
- 16 V
- Voltage - Supply (Vcc/Vdd):
- 10V ~ 30V
- Duty Cycle:
- -
- Frequency - Switching:
- -
- Power (Watts):
- -
- Fault Protection:
- Current Limiting, Open Loop, Over Temperature, Over Voltage, Short Circuit
- Control Features:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 8-SO
- Mounting Type:
- Surface Mount
AP3781S-13 FAQ
1.How can I place an order for AP3781S-13 through Aetrix?
Please submit a Request for Quotation (RFQ) for AP3781S-13 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 AP3781S-13 reliable?
The price and inventory of AP3781S-13 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AP3781S-13 is usually 5 days.
3.What payment methods are accepted for AP3781S-13?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AP3781S-13 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AP3781S-13?
AP3781S-13 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AP3781S-13 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 AP3781S-13?
For technical support, including AP3781S-13 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AP3781S-13 requirements.
6.How does Aetrix verify that AP3781S-13 is sourced from the original manufacturer or authorized distributors?
All AP3781S-13 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 AP3781S-13 meets industry standards.
7.What is the process for return or replacement of AP3781S-13?
All AP3781S-13 units undergo pre-shipment inspection (PSI). If there is an issue with AP3781S-13, 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 AP3781S-13 part is unused and in its original packaging.
Return procedure for AP3781S-13:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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