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Diodes Incorporated AP3981BS7-13
- Part No.:
- AP3981BS7-13
- Manufacturer:
- Diodes Incorporated
- Category:
- AC DC Converters, Offline Switches
- Package:
- 8-SOIC (0.154", 3.90mm Width), 7 Leads
- Datasheet:
-
AP3981BS7-13.pdf
- Description:
- IC OFFLINE SWITCH FLYBACK 7SO
- Quantity:
- Payment:
- Shipping:
Inventory:15,017
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Product details
Overview
AP3981BS7-13 from Diodes Incorporated is a primary-side regulated (PSR) flyback power switcher integrating a 650V N-channel MOSFET and controller in SO-7 package. It delivers accurate constant voltage (2.4V FB threshold) and constant current (tONS/tSW = 0.5 above SUVP) regulation for ≤7.5W AC/DC adapters without opto-coupler or secondary-side feedback. Used in router and STB power supplies, it achieves 75mW no-load input power and operates in valley-on PFM/AM modes to suppress audible noise.
For engineers reviewing the AP3981BS7-13 datasheet, AP3981BS7-13 pinout, AP3981BS7-13 application, or AP3981BS7-13 equivalent, key selection criteria include its integrated 650V MOSFET (RDS(ON) = 7.8–9.3Ω), multi-segment VCS threshold control (560–700mV), SOVP/SUVP/SCP protection thresholds, and SO-7 thermal resistance (θJA = 77°C/W).
Technical Context
The AP3981BS7-13 implements primary-side regulation via auxiliary winding sampling at FB pin, using tONS detection for CC control and line-compensated peak current sensing (RLINE = 45–65Ω) to maintain output current accuracy across universal input. Its valley-on switching (tVAL-ON = 26–38μs) reduces turn-on loss and improves EMI through natural jitter.
It combines three protection mechanisms triggered directly from FB pin voltage: SOVP (3.3–3.9V), SUVP (1.22–1.48V with 116–140ms delay), and SCP (680–820mV with 58–70ms delay), all enabling auto-recovery after VCC drops to 6.1–7.5V. Internal OTP (125–155°C) and VCC OVP (29.5–34.5V) provide full-system fault coverage.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VDS Rating | 650V - Enables direct operation from universal AC input (85–265VRMS) without external HV MOSFET. |
| RDS(ON) | 7.8–9.3Ω - Determines conduction loss and thermal rise in SO-7 package at 1.5A continuous drain current. |
| VFB Threshold | 2.35–2.45V - Sets precise CV output via resistor divider on auxiliary winding; enables ±1% output voltage regulation. |
| VCS_H/VCS_L | 560–700mV / 160–200mV - Dual current-sense thresholds enable load-dependent PFM/AM mode transition to avoid <20kHz audible noise. |
| tVAL-ON | 26–38μs - Defines minimum off-time window for valley switching; ensures ZVS turn-on to reduce EMI and improve efficiency. |
| VCC OVP | 29.5–34.5V - Protects internal bias circuitry during transient overvoltage; triggers immediate shutdown and auto-recovery. |
| θJA | 77°C/W - Specifies thermal performance on standard FR-4 PCB (2oz Cu, 1in² cooling area); critical for 7.5W output derating. |
Pinout & Package
AP3981BS7-13 is housed in a surface-mount SO-7 package with exposed drain pads (pins 5 & 6) for thermal dissipation and isolation compliance. The package supports high-voltage creepage and meets RoHS 3, halogen-free, and antimony-free "Green" requirements.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 NC | No Connection | Unused pad; must remain unconnected to avoid parasitic coupling or latch-up risk. |
| 2 FB | Multi-function Feedback Input | Samples auxiliary winding voltage for CV control, detects tONS for CC regulation, senses line voltage for compensation, and monitors FB-negative for fault detection. |
| 3 VCC | Bias Supply Input | Provides IC operating power; includes UVLO (14.5–17.5V startup) and OVP (29.5–34.5V) protection. |
| 4 SOURCE | MOSFET Source Terminal | Current sense node for RCS; connects to ground reference for peak current detection and leading-edge blanking (330–510ns). |
| 5,6 DRAIN | MOSFET Drain Terminal | High-side switching node connected to primary transformer winding; rated for 650V breakdown and handles full primary current. |
| 7 GND | Power Ground Reference | Common return path for internal regulator, driver, and protection comparators; requires low-impedance PCB layout. |
Key Features
| Feature | Design Value |
|---|---|
| Primary-side regulation | Eliminates opto-coupler and TL431, reducing BOM count by ≥3 components and improving long-term reliability in AC/DC adapters. |
| Valley-on switching | Reduces MOSFET turn-on loss and radiated EMI by synchronizing gate drive with transformer resonant valley, verified by tVAL-ON = 26–38μs spec. |
| Capacitive load start-up | Enables fast output ramp-up via dual tONS/tSW (0.75 → 0.5) transition when VOUT crosses SUVP threshold, preventing brown-out during bulk capacitor charging. |
| 3-segment AM/PFM control | Maintains switching frequency >20kHz across 2–100% load by dynamically adjusting VCS threshold (VCS_L → VCS_M → VCS_H), suppressing audible noise. |
| Integrated line compensation | Uses internal RLINE (45–65Ω) and external RFB1 to correct CC error caused by propagation delay; enables ±3% current accuracy over 85–265VAC. |
Applications
| Router Power Supply | Set-Top Box (STB) Adapter |
|---|---|
Use Scenario: Compact 5V/1.2A AC/DC adapter powering IEEE 802.11ac Wi-Fi routers with strict no-load power (<100mW) requirements. IC Role / Device Role / Timing Role: Primary-side regulated flyback controller with integrated 650V MOSFET; manages tONS-based CC regulation and valley-on timing for ZVS. Use Value: Achieves 75mW no-load input power and eliminates opto-coupler, reducing adapter size and cost while meeting Energy Star Tier 2 standby limits. |
Use Scenario: Wall-mounted 12V/0.6A power supply for digital cable STBs requiring robust short-circuit and overvoltage protection. IC Role / Device Role / Timing Role: PSR controller executing SOVP (3.3–3.9V) and SCP (680–820mV) monitoring via FB pin; uses 128ms SUVP delay to prevent nuisance tripping during cold start. Use Value: Delivers auto-recovery protection without secondary sensing, enabling single-layer PCB design and eliminating 100% duty-cycle failure risk in field-deployed units. |
| Network Adaptor | Low-Power IoT Gateway |
Use Scenario: Universal-input 9V/0.8A adapter for Ethernet-to-WiFi bridges with variable line voltage (85–265VAC) and tight CC tolerance (±5%). IC Role / Device Role / Timing Role: Line-compensated PSR controller using RFB1-adjustable VLC to maintain constant current across input range; employs tSAMPLE ratio (50–80% of tONS) for CV accuracy. Use Value: Maintains ±3% CC accuracy without trim pots or secondary calibration, reducing production test time and field failure rate in high-volume adaptor manufacturing. |
Use Scenario: 5V/1A embedded power supply for battery-backed smart home hubs requiring low-temperature operation (−40°C) and thermal foldback. IC Role / Device Role / Timing Role: Integrated OTP controller with 125–155°C shutdown and +27–33°C hysteresis; uses θJA = 77°C/W to define safe operating area on compact 2-layer PCB. Use Value: Prevents thermal runaway in sealed enclosures by triggering graceful shutdown before junction exceeds 150°C, extending product lifetime in unventilated deployments. |
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 |
|---|---|---|---|
| MP6004DJ-LF-Z | Integrates 700V MOSFET but lacks built-in line compensation and valley-on timing; uses fixed-frequency PWM instead of PFM/AM. | Requires external line-compensation circuitry and has higher audible noise at light load due to absence of multi-segment VCS control. | Select when fixed-frequency EMI profile is preferred over ultra-low no-load power; verify tONS detection compatibility with existing transformer design. |
| LNK364PG | Offers lower no-load power (30mW) but uses external MOSFET and lacks integrated SOVP/SUVP; relies on external Zener for output overvoltage clamping. | Needs additional components for full protection set, increasing BOM cost and board area; not suitable for space-constrained STB adapters. | Choose for ultra-low standby applications where external MOSFET layout flexibility outweighs integration benefits and protection completeness. |
Compared with MP6004DJ-LF-Z and LNK364PG, AP3981BS7-13 uniquely combines SO-7 integration, multi-segment AM/PFM, and FB-pin-based SOVP/SUVP/SCP in a single chip-enabling smaller adapters with fewer components, lower audible noise, and faster time-to-market for router and STB designs.
Availability
AP3981BS7-13 is available at Aetrix Electronics and suitable for router power supplies, set-top box adapters, and network adaptors requiring stable component supply, consistent parametric performance, and long-term lifecycle support.
Supply support for AP3981BS7-13 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, specializing in power management, signal integrity, and protection solutions for consumer, industrial, and computing markets.
The AP3981B belongs to Diodes' PSR AC/DC controller product line, engineered specifically for cost-sensitive, low-power (<10W) offline adapters where opto-coupler elimination, low no-load power, and comprehensive protection are mandatory design requirements.
FAQ
What is the maximum recommended output power for AP3981BS7-13?
The AP3981BS7-13 is rated for up to 7.5W output power in flyback topology under DCM operation with proper SO-7 thermal management. This limit accounts for RDS(ON) = 7.8–9.3Ω, θJA = 77°C/W, and 1.5A continuous drain current-exceeding this requires derating or forced-air cooling per Diodes' DS41422 Rev. 2-2 thermal curves.
How does AP3981BS7-13 achieve constant current without secondary-side sensing?
It measures tONS (secondary diode conduction time) via the FB pin during each switching cycle. Since tONS is proportional to output current in flyback PSR systems, the controller adjusts switching frequency to maintain tONS/tSW = 0.5 above SUVP (1.22–1.48V), delivering precise CC regulation without opto-coupler or shunt regulator.
Can AP3981BS7-13 be used with non-isolated buck-derived topologies?
No-AP3981BS7-13 is designed exclusively for isolated flyback topology in DCM mode. Its FB pin sampling, tONS detection, valley-on timing, and transformer saturation protection rely on flyback waveforms and auxiliary winding coupling; attempting use in buck or buck-boost will result in unstable regulation or protection faults.
What is the purpose of the NC pin (Pin 1) in SO-7 package?
Pin 1 is a no-connect terminal intentionally left unassigned to maintain SO-7 mechanical symmetry and manufacturability. It must remain floating-connecting it to any net may cause internal latch-up or degrade ESD robustness, as confirmed by Diodes' pin description table and absolute maximum ratings for VFB and VCC.
AP3981BS7-13 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diodes Incorporated
- Series:
- -
- Package/Case:
- 8-SOIC (0.154", 3.90mm Width), 7 Leads
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Output Isolation:
- Isolated
- Internal Switch(s):
- Yes
- Voltage - Breakdown:
- 650V
- Topology:
- Flyback
- Voltage - Start Up:
- 16 V
- Voltage - Supply (Vcc/Vdd):
- 10V ~ 28V
- Duty Cycle:
- -
- Frequency - Switching:
- -
- Power (Watts):
- 7.5 W
- Fault Protection:
- Current Limiting, Open Loop, Over Load, Over Temperature, Over Voltage, Short Circuit
- Control Features:
- -
- Operating Temperature:
- -40°C ~ 85°C (TA)
- Grade:
- -
- Qualification:
- -
- Supplier Device Package:
- 7-SO
- Mounting Type:
- Surface Mount
AP3981BS7-13 FAQ
1.How can I place an order for AP3981BS7-13 through Aetrix?
Please submit a Request for Quotation (RFQ) for AP3981BS7-13 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 AP3981BS7-13 reliable?
The price and inventory of AP3981BS7-13 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for AP3981BS7-13 is usually 5 days.
3.What payment methods are accepted for AP3981BS7-13?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for AP3981BS7-13 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for AP3981BS7-13?
AP3981BS7-13 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your AP3981BS7-13 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 AP3981BS7-13?
For technical support, including AP3981BS7-13 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your AP3981BS7-13 requirements.
6.How does Aetrix verify that AP3981BS7-13 is sourced from the original manufacturer or authorized distributors?
All AP3981BS7-13 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 AP3981BS7-13 meets industry standards.
7.What is the process for return or replacement of AP3981BS7-13?
All AP3981BS7-13 units undergo pre-shipment inspection (PSI). If there is an issue with AP3981BS7-13, 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 AP3981BS7-13 part is unused and in its original packaging.
Return procedure for AP3981BS7-13:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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