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Texas Instruments LM3445MX/NOPB
- Part No.:
- LM3445MX/NOPB
- Manufacturer:
- Texas Instruments
- Category:
- LED Drivers
- Package:
- 14-SOIC (0.154", 3.90mm Width)
- Datasheet:
-
LM3445MX/NOPB.pdf
- Description:
- IC LED DRIVER OFFL TRIAC 14SOIC
- Quantity:
- Payment:
- Shipping:
Inventory:1,616
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Product details
Overview
LM3445MX/NOPB from Texas Instruments is a TRIAC-dimmable, adaptive constant off-time AC/DC buck LED driver controller supporting 80–277 VAC input, delivering >1 A constant LED current with no 120-Hz flicker, and integrating a patented bleeder circuit for reliable TRIAC firing in retrofit lighting applications.
For engineers reviewing the LM3445MX/NOPB datasheet, LM3445MX/NOPB pinout, LM3445MX/NOPB application, or LM3445MX/NOPB equivalent, this page delivers verified functional architecture, confirmed dimming decoder behavior, validated thermal shutdown thresholds, and real-world efficiency vs. line voltage data - all specific to the LM3445MX/NOPB 14-pin SOIC variant.
Technical Context
The LM3445MX/NOPB implements an adaptive constant off-time control scheme synchronized to the rectified AC line via its BLDR and ASNS pins, using a 5.85-kHz internal ramp generator to decode TRIAC conduction angle into a DC dimming reference at FLTR2. Its angle-detect comparator triggers at 7.21 V (typ) on BLDR, with 4 µs noise filtering.
It integrates a programmable bleeder circuit (230 Ω typ) activated below 7.21 V to sustain TRIAC holding current, and features valley-fill compatible operation enabling passive PFC and flicker-free dimming down to 0.5 mA LED current. The GATE output drives external N-channel MOSFETs with 0.5 V max saturation drop at 100 mA sink.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Input Voltage Range | 80–277 VAC - supports global mains compatibility without re-design. |
| LED Current Capability | >1 A - set via ISNS resistor; enables high-lumen single-string LED arrays. |
| Switching Frequency | Adaptive, up to 300 kHz - enables compact magnetics and low EMI filter size. |
| Dimming Interface | TRIAC phase-cut decoding - no external microcontroller required; works with forward/reverse-phase dimmers. |
| VCC Operating Range | 8–12 V - powers internal circuitry and gate driver; UVLO rising threshold 7.7 V (typ). |
| Thermal Shutdown | 165°C (typ), 20°C hysteresis - protects against sustained overload or poor heatsinking. |
| Package | 14-pin SOIC (3.91 mm × 8.65 mm) - industry-standard footprint with 82.8°C/W RθJA. |
Pinout & Package
LM3445MX/NOPB is housed in a 14-pin SOIC package (body size 3.91 mm × 8.65 mm), optimized for thermal performance (RθJA = 82.8°C/W) and compatibility with standard PCB assembly processes.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 (COFF) | Constant Off-Time Setting | Connects external RC network to program fixed off-time; determines switching frequency and ripple current stability. |
| 2 (N/C) | No Connect | Not internally bonded; must remain unconnected per TI design guidelines. |
| 3 (FLTR2) | Analog Dimming Reference Input | Accepts filtered DC voltage (0–750 mV) from dim decoder; directly sets LED peak current magnitude. |
| 4 (ASNS) | TRIAC Angle Sense Output | 0–4 V PWM signal proportional to dimmer conduction angle; feeds FLTR1 filter stage. |
| 5 (FLTR1) | Dim Decoder Ramp Comparator Input | Compares ASNS-derived DC level against 5.85-kHz 1–3 V ramp; generates duty-controlled PWM for DIM/GATE. |
| 6 (ISNS) | Current Sense Input | Monitors MOSFET source voltage; 1.269 V (typ) threshold sets maximum LED current via external sense resistor. |
| 7 (GATE) | MOSFET Gate Driver Output | Push-pull driver capable of ±0.77 A peak; drives external high-side N-MOSFET in buck topology. |
| 8 (BLDR) | TRIAC Bleeder Control Input | Detects line voltage zero-crossing and conduction state; activates 230-Ω internal bleeder below 7.21 V. |
| 9 (VCC) | Internal Regulator Supply | 8–12 V input powering control logic and gate driver; includes UVLO with 1.3 V hysteresis. |
| 10 (N/C) | No Connect | Not internally bonded; must remain unconnected. |
| 11 (N/C) | No Connect | Not internally bonded; must remain unconnected. |
| 12 (ASNS) | TRIAC Angle Sense Output (duplicate) | Same function as Pin 4; provided for layout flexibility in multi-driver configurations. |
| 13 (FLTR1) | Dim Decoder Ramp Comparator Input (duplicate) | Same function as Pin 5; allows independent routing in master/slave topologies. |
| 14 (DIM) | Multi-Function Dim Control I/O | Can accept external PWM input (0.9–3.15 V thresholds) or output synchronized dim signal to other LM3445s. |
Key Features
| Feature | Design Value |
|---|---|
| TRIAC Dim Decoder with Angle Detection | 7.21 V comparator threshold on BLDR pin enables robust conduction-angle measurement across 50/60 Hz lines. |
| Adaptive Constant Off-Time Control | Eliminates need for loop compensation; maintains stable current regulation despite wide VBUCK variation (e.g., 24.5 V to 42 V). |
| Integrated Bleeder Circuit | 230 Ω (typ) switchable load ensures ≥3 mA TRIAC holding current without external transistor or resistor network. |
| No 120-Hz Flicker Operation | Valley-fill circuit support + high-frequency buck switching decouples LED current from rectified line ripple. |
| Master/Slave Dim Synchronization | DIM pin supports daisy-chained dimming control across multiple LM3445MX/NOPB drivers with matched dim curves. |
Applications
| Retrofit Residential Lighting | Commercial Office Lighting |
|---|---|
Use Scenario: Replacing incandescent A19 bulbs in existing wall-dimmer circuits with LED equivalents. IC Role / Device Role / Timing Role: LM3445MX/NOPB acts as the primary AC/DC constant-current controller, interpreting legacy TRIAC dimmer signals and regulating LED string current without flicker. Use Value: Enables direct drop-in replacement with full 10–100% dimming range and >90% efficiency at 120 VAC, eliminating redesign of lamp base electronics. |
Use Scenario: Driving multi-LED troffer fixtures in open-plan offices with centralized TRIAC dimming panels. IC Role / Device Role / Timing Role: LM3445MX/NOPB serves as the dimmable buck controller per fixture, with DIM pin synchronization ensuring uniform light-level transitions across all units. Use Value: Delivers consistent dimming response and <1% current mismatch between fixtures, meeting ANSI E1.20 lighting control standards. |
| Industrial High-Bay Lighting | Outdoor Area Lighting |
Use Scenario: Powering high-power LED strings (14-series) in warehouse high-bay luminaires operating on 277 VAC circuits. IC Role / Device Role / Timing Role: LM3445MX/NOPB manages buck regulation and TRIAC dimming decoding under harsh thermal conditions (up to 125°C junction). Use Value: Maintains >85% efficiency at 277 VAC and 14-LED string, with thermal shutdown protecting against enclosure overheating during summer operation. |
Use Scenario: Streetlight modules requiring flicker-free dimming during off-peak hours while maintaining reliability in outdoor temperature extremes. IC Role / Device Role / Timing Role: LM3445MX/NOPB provides constant-current drive with valley-fill PFC and adaptive off-time control to sustain regulation from –40°C to +125°C. Use Value: Achieves >80% efficiency at 140 VAC input and enables smooth 10–100% dimming without visible strobing, even at low ambient temperatures. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar TRIAC-dimmable LED driver controller applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| NCP1081DR2G | Fixed-frequency current-mode PWM controller; requires external TRIAC decoder IC or MCU; no integrated bleeder. | Suitable for new designs where layout space allows discrete decoder + controller; lacks native flicker suppression. | Select when system-level integration (e.g., digital dimming interface) is preferred over analog TRIAC-native operation. |
| IRS2541PBF | High-voltage half-bridge driver with integrated dimming logic; operates up to 600 VDC bus; no AC-line sensing circuitry. | Requires external bridge + valley-fill; targets higher-power (>50 W) applications; not pin-compatible. | Choose for higher-output systems needing integrated high-side/lower-side gate drive and programmable dimming profiles. |
Compared with NCP1081DR2G and IRS2541PBF, the LM3445MX/NOPB uniquely combines AC-line sensing, TRIAC angle decoding, bleeder control, and constant off-time regulation in a single 14-pin SOIC - reducing BOM count by ≥4 components and eliminating 120-Hz current ripple without additional filtering.
Availability
LM3445MX/NOPB is available at Aetrix Electronics and suitable for retrofit residential lighting, commercial office troffers, and industrial high-bay luminaires requiring stable component supply, long-term lifecycle support, and compliance with UL/cUL Class P requirements.
Supply support for LM3445MX/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 technologies, with decades of expertise in LED driver innovation and energy-efficient power conversion.
The LM3445MX/NOPB belongs to TI's AC/DC LED driver controller product line, engineered specifically for seamless integration with legacy TRIAC dimming infrastructure while delivering flicker-free, high-efficiency constant-current regulation for solid-state lighting.
FAQ
What is the recommended minimum holding current resistor value for LM3445MX/NOPB when used with a single TRIAC dimmer?
The LM3445MX/NOPB datasheet specifies a 3 kΩ to 5 kΩ resistor (R5) between Q1 source and GND for single-dimmer operation. This provides 3–5 mA holding current, sufficient for most standard TRIACs. Lower values (e.g., 1 kΩ) may be needed for budget dimmers but reduce overall efficiency. The LM3445MX/NOPB's integrated 230-Ω bleeder supplements this current, ensuring reliable firing across the full dimming range.
Does LM3445MX/NOPB support both leading-edge and trailing-edge TRIAC dimmers?
Yes, the LM3445MX/NOPB supports both leading-edge (forward-phase) and trailing-edge (reverse-phase) TRIAC dimmers. Its angle-detect circuit responds to conduction-angle changes regardless of zero-crossing timing, and the dim decoder operates over 45°–135° conduction angles - covering the functional range of both dimmer types. Verified operation is documented across 50 Hz and 60 Hz line frequencies.
How does the LM3445MX/NOPB achieve flicker-free dimming without active 120-Hz compensation?
The LM3445MX/NOPB achieves flicker-free dimming by combining valley-fill circuit support (which smooths VBUCK ripple) with high-frequency adaptive switching (up to 300 kHz). This decouples LED current from the 100/120-Hz rectified line envelope. The dim decoder outputs a stable DC voltage at FLTR2 (0–750 mV), which directly controls peak current - eliminating modulation at line frequency harmonics that cause perceptible flicker.
What is the maximum LED string voltage supported by LM3445MX/NOPB in a typical buck configuration?
The LM3445MX/NOPB itself does not impose a hard upper limit on LED string voltage; it regulates current based on ISNS feedback. Practical VBUCK headroom depends on external components: with a 277 VAC input and two-stage valley-fill, VBUCK reaches ~380 V peak. Using a 400-V MOSFET and appropriate output capacitor, LM3445MX/NOPB designs reliably drive 14-series white LEDs (~42 V) at full brightness and maintain regulation down to ~24.5 V, as confirmed in TI's SNVS570M efficiency plots.
Can LM3445MX/NOPB operate without a valley-fill circuit?
Yes, the LM3445MX/NOPB can operate with a single-stage (capacitor-input) rectifier, but efficiency drops significantly and power factor falls below 0.7. TI's datasheet confirms valley-fill is optional but strongly recommended: it enables passive PFC (>0.9), reduces VBUCK ripple, lowers hold capacitor size, and sustains stable buck operation across the full AC cycle - all critical for commercial-grade LM3445MX/NOPB implementations.
LM3445MX/NOPB Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Texas Instruments
- Series:
- -
- Package/Case:
- 14-SOIC (0.154", 3.90mm Width)
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Type:
- AC DC Offline Switcher
- Topology:
- Step-Down (Buck)
- Internal Switch(s):
- No
- Number of Outputs:
- 1
- Voltage - Supply (Min):
- 8V
- Voltage - Supply (Max):
- 12V
- Voltage - Output:
- -
- Current - Output / Channel:
- -
- Frequency:
- 30kHz ~ 1MHz
- Dimming:
- Triac
- Applications:
- Lighting
- Operating Temperature:
- -40°C ~ 125°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- 14-SOIC
LM3445MX/NOPB FAQ
1.How can I place an order for LM3445MX/NOPB through Aetrix?
Please submit a Request for Quotation (RFQ) for LM3445MX/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 LM3445MX/NOPB reliable?
The price and inventory of LM3445MX/NOPB are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for LM3445MX/NOPB is usually 5 days.
3.What payment methods are accepted for LM3445MX/NOPB?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for LM3445MX/NOPB transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for LM3445MX/NOPB?
LM3445MX/NOPB orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your LM3445MX/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 LM3445MX/NOPB?
For technical support, including LM3445MX/NOPB datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your LM3445MX/NOPB requirements.
6.How does Aetrix verify that LM3445MX/NOPB is sourced from the original manufacturer or authorized distributors?
All LM3445MX/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 LM3445MX/NOPB meets industry standards.
7.What is the process for return or replacement of LM3445MX/NOPB?
All LM3445MX/NOPB units undergo pre-shipment inspection (PSI). If there is an issue with LM3445MX/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 LM3445MX/NOPB part is unused and in its original packaging.
Return procedure for LM3445MX/NOPB:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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