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Texas Instruments LM3447MT/NOPB
- Part No.:
- LM3447MT/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 14-TSSOP (0.173", 4.40mm Width)
- Datasheet:
-
LM3447MT/NOPB.pdf
- Description:
- IC LED DRIVER OFFL TRIAC 14TSSOP
- Quantity:
- Payment:
- Shipping:
Inventory:1,984
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Product details
Overview
LM3447MT/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 parameters: 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 thermal foldback with 1 V TSNS trip threshold. It enables compact, single-stage isolated LED drivers for A19/R20/ PAR30 lamps.
For engineers reviewing the LM3447MT/NOPB datasheet, LM3447MT/NOPB pinout, LM3447MT/NOPB application, or LM3447MT/NOPB equivalent, this page delivers verified technical context, real-world dimming behavior, primary-side control architecture, and validated alternative options - all grounded in TI's SNOSC65A datasheet and functional block diagram.
Technical Context
The LM3447MT/NOPB uses a proprietary primary-side control scheme where input power is regulated via feedforward from rectified AC line voltage (VAC) through FF pin sourcing 10 μA per 100 μA VAC current. Its valley-switching operation relies on AUX pin sensing auxiliary winding zero-crossings with 1.75 V OVP threshold and 4 μs timeout.
Dimming is implemented by decoding phase angle via FLT1/FLT2 interface: FLT2 accepts filtered dimmer waveform and triggers internal decode gain of 0.877 V/V, while HOLD pin drives external pre-regulator FET with 24 Ω RDS(ON) to sustain TRIAC conduction during zero crossings.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Oscillator period | 14.5 μs typical - sets fixed-frequency DCM switching at ~69 kHz for low EMI and predictable power delivery |
| Current sense threshold | 275 mV typical - defines cycle-by-cycle FET overcurrent protection point referenced to ISNS pin |
| VCC UVLO rising threshold | 10.5 V - ensures reliable startup only after bias supply reaches operational margin |
| TSNS thermal foldback threshold | 1.0 V typical - triggers LED power reduction when NTC voltage falls below threshold due to temperature rise |
| Hold MOSFET RDS(ON) | 24 Ω - enables efficient TRIAC hold current management without external driver transistor |
| Feedforward gain | GFF = 10 - linearly maps VAC current to FF source current for accurate input power regulation |
| AUX OVP threshold | 1.75 V - protects against transformer auxiliary winding overvoltage during off-time |
Pinout & Package
TSSOP-14 package with exposed pad (MTC14 drawing); thermally enhanced for continuous operation up to 125°C junction temperature.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| VAC | Input voltage feedforward and dimmer angle sensing | Current-fed node that sets power regulation setpoint and enables leading/trailing-edge dimmer compatibility |
| TSNS | Thermal foldback input | Connects to NTC resistor to reduce LED power as temperature rises - 1.0 V trip threshold ensures lifetime protection |
| FLT1 | Dimmer angle filter output | Drives external RC low-pass filter to condition raw dimmer waveform before decoding at FLT2 |
| FLT2 | Dimmer decode input | Accepts filtered signal; internal 0.877× gain converts to INV reference for PWM ramp adjustment |
| HOLD | TRIAC hold current driver | Sinks current through external resistor to maintain TRIAC conduction during AC zero crossings |
| BIAS | Pre-regulator clamp reference | Clamped at 17.7 V during startup and 13.5 V post-UVLO - controls QPASS pass transistor in linear bias supply |
| AUX | Valley detection and OVP sense | Detects transformer auxiliary winding zero-crossing for valley switching; trips at 1.75 V for OVP protection |
| VCC | Internal supply rail | Powered by bootstrap or linear bias; UVLO (10.5 V↑ / 7.5 V↓) and OVP (18.9 V↑) ensure safe operation |
| FF | Feedforward current source | Sources 10 μA per 100 μA VAC current - directly scales duty cycle to input voltage for line regulation |
| INV | Error amplifier inverting input | Receives FF voltage or opto-isolator output; compares to 1.0 V internal reference for closed-loop regulation |
| COMP | Error amplifier output | Integrates error signal; connects to capacitor for loop compensation - minimum 280 mV required to enable GATE |
| GATE | Power FET gate driver | Push-pull output capable of driving >1 nF gate capacitance; disabled during fault or UVLO |
| ISNS | Primary current sense | Monitors switch current via sense resistor; trips at 275 mV for cycle-by-cycle overcurrent protection |
| GND | Signal and power ground | Common return for all analog and digital circuitry - requires low-impedance PCB connection |
Key Features
| Feature | Design Value |
|---|---|
| Integrated phase-angle decoder | Supports both leading- and trailing-edge dimmers with >50:1 dimming range - eliminates need for external decoder IC |
| Primary-side input power regulation | Uses VAC feedforward to regulate LED power without secondary-side feedback - reduces BOM count and cost |
| Valley switching operation | Reduces switching loss and EMI by turning on FET at transformer demagnetization zero-crossing - enabled via AUX pin sensing |
| Efficient TRIAC hold current management | HOLD pin drives external resistor to sustain dimmer conduction - avoids flicker and dropout at low dim levels |
| Thermal foldback with single NTC | TSNS pin interfaces directly with one external NTC resistor - provides LED lifetime protection without extra components |
Applications
| Dimmable Residential LED Lamps | Commercial Recessed Downlights |
|---|---|
Use Scenario: A19 or PAR30 retrofit lamp operating from 120 VAC with TRIAC wall dimmer. IC Role / Device Role / Timing Role: LM3447MT/NOPB acts as primary-side PFC flyback controller, regulating input power to maintain constant LED wattage across dimming range. Use Value: Achieves >50:1 dimming range with no visible flicker and PF >0.9 at 10% dim level - meets ENERGY STAR requirements. | Use Scenario: 15–25 W recessed downlight in office ceiling with ELV or TRIAC dimmer. IC Role / Device Role / Timing Role: LM3447MT/NOPB manages valley-switched DCM flyback with thermal foldback to protect LEDs during high-ambient operation. Use Value: Enables single-stage design with <15 mm height profile and 90 lm/W efficacy - eliminates bulky secondary feedback circuitry. |
| Industrial LED Pendant Lights | Dimmable Solid-State Lighting Modules |
Use Scenario: 20–30 W pendant light in warehouse with 0–10 V or phase-cut dimming interface. IC Role / Device Role / Timing Role: LM3447MT/NOPB serves as core controller implementing primary-side power regulation and AUX-based valley detection. Use Value: Delivers ±3% line regulation over 90–305 VAC input and maintains constant lumen output despite LED forward voltage drift. | Use Scenario: OEM LED module for integration into smart lighting fixtures with thermal monitoring requirement. IC Role / Device Role / Timing Role: LM3447MT/NOPB provides integrated thermal foldback via TSNS and fault timer-based burst mode for short-circuit protection. Use Value: Reduces system-level thermal derating by 25% compared to fixed-current drivers - extends usable ambient temperature range to 85°C. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar PFC flyback controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| UCC28063DR | Fixed-frequency DCM PFC + QR flyback combo controller; no integrated dimmer decode or HOLD driver | Requires external phase decoder and TRIAC hold circuit; better suited for non-dimming high-efficiency designs | Select UCC28063DR when designing non-dimmable industrial LED drivers needing tighter THD and higher efficiency |
| NCP1654ADR2G | Single-stage DCM PFC controller with analog dimming input; lacks valley switching and integrated HOLD FET driver | Needs external valley detect circuit and separate hold current path; supports analog 0–10 V dimming but not phase-cut | Select NCP1654ADR2G for cost-sensitive commercial lighting where phase-cut dimming is not required |
Compared with UCC28063DR and NCP1654ADR2G, the LM3447MT/NOPB uniquely integrates phase-angle decoding, HOLD current management, and valley switching in a single TSSOP-14 package - enabling flicker-free dimming down to 1% without additional ICs or layout complexity.
Availability
LM3447MT/NOPB is available at Aetrix Electronics and suitable for dimmable residential LED lamps, commercial downlights, and industrial pendant lights requiring stable component supply and long-term production continuity.
Supply support for LM3447MT/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 company headquartered in Dallas, Texas, delivering analog and embedded processing solutions for industrial, automotive, and consumer markets.
The LM3447MT/NOPB belongs to TI's LED lighting controller product line, designed specifically for compact, single-stage, phase-dimmable AC-DC LED drivers targeting 5–30 W output power with minimal external components.
FAQ
What is the primary function of the LM3447MT/NOPB in an LED driver design?
The LM3447MT/NOPB serves as a phase-dimmable, primary-side power-regulated PFC flyback controller. It regulates input power using input voltage feedforward, decodes dimmer phase angle via FLT1/FLT2, manages TRIAC hold current through the HOLD pin, and implements valley switching via AUX sensing - all within a single TSSOP-14 package. This enables compact, flicker-free dimming for A19, PAR30, and downlight applications without secondary feedback.
How does the LM3447MT/NOPB achieve constant LED power across input voltage variations?
The LM3447MT/NOPB achieves constant LED power using a primary-side input voltage feedforward technique. The VAC pin senses rectified line current, and the FF pin sources current proportional to VAC (GFF = 10). This feeds the error amplifier (INV/COMP), adjusting PWM duty cycle to maintain constant input power - resulting in ±3% line regulation over 90–305 VAC without optocoupler or secondary sensing.
What is the role of the TSNS pin on the LM3447MT/NOPB?
The TSNS pin on the LM3447MT/NOPB interfaces with an external NTC thermistor to implement thermal foldback protection. When the NTC voltage drops below 1.0 V (typical TSNS(TH)), the controller reduces LED power to prevent overheating and extend lifetime. The internal 7.88 kΩ pull-up resistor (at 25°C) forms a voltage divider with the NTC, enabling precise temperature-dependent dimming without additional circuitry.
Can the LM3447MT/NOPB support both leading-edge and trailing-edge dimmers?
Yes, the LM3447MT/NOPB supports both leading-edge (TRIAC) and trailing-edge (electronic low-voltage) dimmers. Its integrated phase-angle decoder uses FLT1/FLT2 pins with 0.877× decode gain to interpret dimmer conduction angle accurately. Confirmed in TI's SNOSC65A datasheet, this enables smooth, flicker-free dimming over >50:1 range regardless of dimmer type - eliminating need for external decoder ICs.
What protection features are built into the LM3447MT/NOPB?
The LM3447MT/NOPB includes LED open-circuit and short-circuit protection, cycle-by-cycle FET overcurrent protection (via ISNS pin at 275 mV), internal 812 ms fault timer for burst-mode recovery, thermal foldback (TSNS), VCC overvoltage protection (18.9 V), and thermal shutdown (165°C). These features are documented in the Electrical Characteristics table and Functional Block Diagram of the SNOSC65A datasheet.
LM3447MT/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-TSSOP (0.173", 4.40mm Width)
- Packaging:
- Tube
- 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
LM3447MT/NOPB FAQ
1.How can I place an order for LM3447MT/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3447MT/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 LM3447MT/NOPB reliable?
The price and inventory of LM3447MT/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3447MT/NOPB is usually 5 days.
3.What payment methods are accepted for LM3447MT/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3447MT/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3447MT/NOPB?
LM3447MT/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3447MT/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 LM3447MT/NOPB?
For technical support, including LM3447MT/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3447MT/NOPB requirements.
6.How does Aetrix verify that LM3447MT/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3447MT/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 LM3447MT/NOPB meets industry standards.
7.What is the process for return or replacement of LM3447MT/NOPB?
All LM3447MT/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3447MT/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 LM3447MT/NOPB part is unused and in its original packaging.
Return procedure for LM3447MT/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
LM3447MT/NOPB Tags
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