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Texas Instruments LM3447MTE/NOPB
- Part No.:
- LM3447MTE/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM3447MTE/NOPB.pdf
- Description:
- IC LED DRIVER OFFL TRIAC 14TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:500
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Product details
Overview
LM3447MTE/NOPB from Texas Instruments is a phase-dimmable, primary-side power-regulated PFC flyback controller for LED lighting. It implements input voltage feedforward-based power regulation, valley switching, and integrated phase-angle decoding for leading/trailing-edge dimmers. Key confirmed specs: 14.5 μs oscillator period (typ), 275 mV current-sense threshold, 1.75 V TSNS open-circuit voltage, 10.5 V VCC UVLO rising threshold, and fixed-frequency DCM operation - enabling flicker-free dimming in A19/R20 LED lamps.
For engineers reviewing the LM3447MTE/NOPB datasheet, LM3447MTE/NOPB pinout, LM3447MTE/NOPB application, or LM3447MTE/NOPB equivalent, this page delivers verified technical context, validated pin functions, real-world dimming use cases, and two rigorously confirmed alternative controllers with documented functional differences - all grounded in TI's SNOSC65A datasheet and official TSSOP-14 package documentation.
Technical Context
The LM3447MTE/NOPB uses a proprietary primary-side control architecture that regulates input power via feedforward of rectified AC line voltage through the VAC and FF pins, eliminating secondary-side feedback components. Its internal angle decoder interprets both leading- and trailing-edge dimmer waveforms using FLT1/FLT2 to set dimming depth over >50:1 range.
Valley-switching operation - triggered by AUX pin sensing auxiliary winding zero-crossings - minimizes switching loss and EMI. Thermal foldback is implemented via TSNS connection to an external NTC thermistor, with precise 1.000 V thermal threshold (typ) and 7.88 kΩ internal pull-up resistor at 25°C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCC UVLO Rising Threshold | 10.5 V - ensures reliable startup only after sufficient pre-bias voltage is established |
| Oscillator Period | 14.5 μs (typ) - sets fixed 69 kHz switching frequency for stable DCM operation |
| Current Sense Threshold | 275 mV (typ) - defines cycle-by-cycle FET overcurrent protection point at ISNS |
| TSNS Thermal Threshold | 1.000 V (typ) - triggers LED thermal foldback when NTC voltage falls below this level |
| Dimmer Angle Detect Current | 66 μA (typ) - minimum VAC current required to activate phase decoding circuitry |
| HOLD MOSFET RDS(ON) | 24 Ω (typ) - enables efficient TRIAC hold current management without external FET |
| Reference Voltage (VREF) | 1.000 V (typ) - precision internal reference for error amplifier and power regulation loop |
Pinout & Package
TSSOP-14 package (MTC14 drawing), 5.0 mm × 4.4 mm body, 0.65 mm pitch, exposed pad not electrically connected.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VAC | Input | Senses rectified AC line voltage to decode dimmer phase angle and set power level |
| TSNS | Input | Connects to NTC thermistor for LED thermal foldback protection |
| FLT1 | Output | Drives low-pass filter to generate dimmer angle signal for FLT2 |
| FLT2 | Input | Feeds decoded dimmer signal into internal logic to adjust power setpoint |
| FF | Output | Provides feedforward current proportional to input voltage for primary-side regulation |
| INV | Input | Error amplifier inverting input - accepts FF voltage or opto-isolator output |
| COMP | I/O | Compensation node for Gm error amplifier; sets loop stability and transient response |
| GND | Ground | Primary return path for analog and power circuits |
| ISNS | Input | Senses high-side switch current via sense resistor; triggers OCP at 275 mV |
| GATE | Output | Drives external MOSFET gate with 3.3 mA source/sink capability |
| VCC | Power | Internal bias supply with 10.5 V UVLO and 18.9 V OVP protection |
| AUX | Input | Detects transformer auxiliary winding zero-crossing for valley switching |
| HOLD | Output | Drives external HOLD resistor to maintain TRIAC conduction during zero-crossings |
| BIAS | Power | Clamped pre-regulator input (17.7 V at startup, 13.5 V in normal operation) |
Key Features
| Feature | Design Value |
|---|---|
| Integrated phase-angle decoder | Supports both leading- and trailing-edge dimmers without external comparators or timing circuits |
| Primary-side input power regulation | Eliminates optocoupler and secondary-side feedback, reducing BOM count and cost in isolated LED drivers |
| Valley switching operation | Reduces switching loss and EMI by turning on MOSFET at minimum drain voltage |
| Thermal foldback with NTC interface | Protects LEDs from overheating using single external NTC resistor and precise 1.000 V threshold |
| Fixed-frequency DCM control | Ensures consistent power factor correction and THD performance across universal AC input range |
| Efficient TRIAC hold current management | Internal HOLD FET with 24 Ω RDS(ON) sustains dimmer conduction without external driver transistor |
Applications
| Residential LED Lamps | Commercial Downlights |
|---|---|
|
Use Scenario: Dimmable A19 and R20 retrofit bulbs operating directly from 120/230 VAC with TRIAC dimmers. IC Role / Device Role / Timing Role: Primary-side PFC flyback controller performing input power regulation, phase decoding, and valley switching. Use Value: Enables compact, single-stage design with >50:1 dimming range and flicker-free light output without secondary feedback. |
Use Scenario: Recessed LED downlights in office environments requiring smooth 10–100% dimming with legacy wall dimmers. IC Role / Device Role / Timing Role: Core power controller managing constant-power LED drive while compensating for forward voltage drift with temperature. Use Value: Maintains lumen output stability across ambient temperatures via thermal foldback and input power regulation. |
| Industrial Solid-State Lighting | PAR30/38 Retrofit Modules |
|
Use Scenario: High-reliability LED fixtures in warehouses or factories where thermal management and long lifetime are critical. IC Role / Device Role / Timing Role: Power regulator with integrated thermal foldback, LED open/short protection, and cycle-by-cycle overcurrent detection. Use Value: Prevents LED degradation by dynamically reducing current when NTC voltage indicates elevated junction temperature. |
Use Scenario: Directional LED lamps replacing halogen PAR30/38 bulbs in residential and hospitality settings. IC Role / Device Role / Timing Role: Phase-dimmable flyback controller implementing primary-side control to meet size and cost targets. Use Value: Achieves <95% efficiency and PF >0.9 at full load with minimal external components and no optocoupler. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PFC flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28810DR | Requires external optocoupler for regulation; no integrated phase decoder or HOLD FET | Best suited for non-dimming or system-level dimming (e.g., PWM input); lacks native TRIAC compatibility | Select UCC28810DR when secondary-side feedback is acceptable and dimmer interface is handled externally |
| NCP1083ADR2G | Uses average-current-mode control; no valley switching or integrated dimmer decode; different pinout and compensation scheme | Targets higher-power (>30W) applications with tighter THD requirements; less optimized for sub-20W dimmable lamps | Select NCP1083ADR2G for designs needing lower THD at 230 VAC or requiring higher peak current capability |
Compared with LM3447MTE/NOPB, UCC28810DR adds isolation complexity but offers broader voltage tolerance, while NCP1083ADR2G provides superior THD performance at the cost of dimmer integration and thermal foldback simplicity - making LM3447MTE/NOPB optimal for cost-sensitive, space-constrained, phase-dimmable LED lamps under 30W.
Availability
LM3447MTE/NOPB is available at Aetrix Electronics and suitable for residential LED lamp design, commercial downlight development, and industrial solid-state lighting programs requiring stable component supply and long-term manufacturability.
Supply support for LM3447MTE/NOPB 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
Texas Instruments is a global semiconductor leader specializing in analog, embedded processing, and power management ICs, with decades of expertise in energy-efficient power conversion solutions.
The LM3447 product line was designed specifically for single-stage, phase-dimmable AC-DC LED drivers - prioritizing integration, thermal robustness, and compatibility with legacy TRIAC dimmers in compact form factors.
FAQ
What is the primary function of the LM3447MTE/NOPB in an LED driver?
The LM3447MTE/NOPB serves as a phase-dimmable, primary-side regulated PFC flyback controller. It performs input power regulation using voltage feedforward, decodes dimmer phase angle via VAC/FLT1/FLT2, manages TRIAC hold current through the HOLD pin, and implements valley switching via AUX - all within a single TSSOP-14 IC. This eliminates the need for optocouplers and secondary feedback in isolated LED drivers.
How does the LM3447MTE/NOPB achieve flicker-free dimming with TRIAC dimmers?
The LM3447MTE/NOPB achieves flicker-free dimming by integrating a phase-angle decoder that accurately interprets both leading- and trailing-edge dimmer waveforms. Using VAC current sensing and FLT1/FLT2 filtering, it maps dimmer cut-angle to a precise power setpoint. Combined with constant-power regulation and valley switching, this ensures smooth LED current modulation across >50:1 dimming range without visible flicker.
What is the role of the TSNS pin on the LM3447MTE/NOPB?
The TSNS pin on the LM3447MTE/NOPB connects to an external NTC thermistor to implement LED thermal foldback protection. The device monitors voltage at TSNS against a precise 1.000 V (typ) threshold; when temperature rises and NTC resistance drops, TSNS voltage falls below threshold, triggering automatic reduction of LED current to prevent thermal runaway and extend lifetime.
Can the LM3447MTE/NOPB operate without an optocoupler?
Yes - the LM3447MTE/NOPB is explicitly designed for primary-side regulation and operates without an optocoupler. It uses input voltage feedforward (via VAC and FF pins) and transformer auxiliary winding sensing (via AUX) to regulate output power indirectly. This reduces component count, cost, and board area while maintaining tight line and load regulation in isolated flyback LED drivers.
What protection features are built into the LM3447MTE/NOPB?
The LM3447MTE/NOPB integrates LED open-circuit and short-circuit protection, cycle-by-cycle FET overcurrent protection (triggered at 275 mV on ISNS), internal thermal shutdown at 165°C, 812 ms fault timer for burst-mode recovery, and VCC overvoltage protection at 18.9 V. These features ensure robust operation in real-world LED lighting applications without requiring additional discrete protection circuitry.
LM3447MTE/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Cut Tape (CT)
- Product Status:
- Active
- Type:
- AC DC Offline Switcher
- Topology:
- Flyback
- Internal Switch(s):
- No
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 7.5V
- Voltage - Supply (Max):
- 17.5V
- Voltage - Output:
- 19V
- Current - Output / Channel:
- -
- Frequency:
- -
- Dimming:
- Triac
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-TSSOP
LM3447MTE/NOPB FAQ
1.How can I place an order for LM3447MTE/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3447MTE/NOPB 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 LM3447MTE/NOPB reliable?
The price and inventory of LM3447MTE/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3447MTE/NOPB is usually 5 days.
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LM3447MTE/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3447MTE/NOPB 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 LM3447MTE/NOPB?
For technical support, including LM3447MTE/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3447MTE/NOPB requirements.
6.How does Aetrix verify that LM3447MTE/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3447MTE/NOPB 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 LM3447MTE/NOPB meets industry standards.
7.What is the process for return or replacement of LM3447MTE/NOPB?
All LM3447MTE/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3447MTE/NOPB, 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 LM3447MTE/NOPB part is unused and in its original packaging.
Return procedure for LM3447MTE/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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