LM3444 - AC-DC Buck LED Driver, Analog Dimming | TI
MPN： LM3444 ✓ 啟用中LM3444 概覽
An AC-DC offline LED driver is a power management IC that converts alternating current (AC) from the mains into regulated direct current (DC) to drive LEDs. It belongs to the LED driver family within the broader power management IC category. The LM3444 uses a buck topology to step down rectified AC voltage to the level required by the LED string while maintaining constant current for consistent brightness and LED longevity.
Key features include adaptive constant off-time control, which simplifies design and improves efficiency across a wide input range suitable for universal mains operation (90VAC to 265VAC). Analog dimming is supported, and a passive power factor correction circuit draws current directly from the line for most of the cycle, achieving good power factor (>0.9) without an active PFC controller. Thermal shutdown and cycle-by-cycle current limit provide robust protection.
The LM3444 operates at high switching frequency (up to 1 MHz), enabling small inductors and capacitors. The internal architecture maintains constant LED current regardless of input voltage variations, and the passive PFC shaping helps reduce harmonic distortion for lighting applications.
Typical applications include LED bulbs, LED tubes, LED downlights, and other general lighting fixtures that require high efficiency, small size, and good power factor. It is also suitable for industrial and commercial lighting systems needing power quality compliance.
When designing with the LM3444, ensure adequate PCB copper area for heat dissipation, and choose the inductor and sense resistor carefully - they directly affect output current accuracy and efficiency. Refer to the TI datasheet for detailed design equations and component selection guidelines. Pricing examples: LM3444MM/NOPB from about $1.27 at LCSC as of 2026-08-29.
直接替換替代品，適用於 LM3444 — 相同封裝，腳位對腳位相容。需重新設計 PCB 的不同封裝零件不列入。
LM3444MM/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LM3444MX/NOPB
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
LM3445
⚡ 相同封裝📋 參考替代品（不在目錄中）
LM3444 最大額定值與電氣特性
| 功能 | AC/DC buck (step-down) constant current LED controller |
| Control Topology | Adaptive constant off-time |
| Outputs | 1 |
| Dimming Method | Analog dimming |
| Power Factor Correction | Passive PFC (power factor > 0.9) |
| 切換頻率 | Up to 1 MHz |
| Input Voltage (Universal Mains) | 90 VAC to 265 VAC |
| Package Options | 10-pin VSSOP or 8-lead SOIC |
| 安裝類型 | Surface Mount |
| Protection Features | Thermal shutdown, cycle-by-cycle current limit |
| Applications | LED bulbs, tubes, downlights, general lighting |
| RoHS 狀態 | Compliant (NOPB / lead-free suffix per TI product page) |
LM3444 10-pin vssop or 8-lead soic 腳位配置指南
LM3444（10-pin vssop or 8-lead soic 封裝）的腳位配置。 此功率元件具有閘極、汲極與源極端子。對於非極性封裝，請參閱製造商資料表以取得確切的第 1 腳方向與佈局詳細資訊。常見應用包括電源設計、馬達驅動與負載切換。
無詳細腳位定義資料： LM3444.
請參閱 資料表 以查看完整腳位配置。
典型應用
LM3444 適用於 6 應用s: LED Bulb (A19 / Retrofit Lamps), LED Tube Lights (T8 Retrofit), LED Downlights and Ceiling Fixtures, General Illumination Power Supplies, Industrial and Commercial Lighting, Dimmable Task and Accent Lighting.
LED Bulb (A19 / Retrofit Lamps)
The LM3444 fits LED bulb designs because its passive PFC circuit draws current directly from the line for most of the cycle, achieving power factor greater than 0.9 without an active PFC stage - important for bulb form factors where component count and height are limited. Its adaptive constant off-time buck control maintains constant LED current across the 90VAC-265VAC universal mains range, keeping brightness stable as line voltage varies. Operation up to 1 MHz allows a small inductor that fits inside an A19 or candle-lamp envelope. Placed after the bridge rectifier with a sense resistor setting LED current, it delivers flicker-free constant current at high efficiency.
推薦
LED Tube Lights (T8 Retrofit)
For T8 LED tube retrofits, the LM3444's high-frequency buck architecture (up to 1 MHz) enables a compact magnetic design that fits the slim tube housing, while passive PFC meets typical commercial lighting power factor requirements (>0.9). The adaptive constant off-time scheme keeps LED string current constant as rectified mains varies, so the tube maintains uniform light output on both 120VAC and 230VAC supplies. Analog dimming input allows integration with simple dimming interfaces. Thermal shutdown and cycle-by-cycle current limit protect the driver during abnormal conditions such as shorted LED strings.
推薦
LED Downlights and Ceiling Fixtures
In commercial LED downlights, the LM3444 provides constant current to the LED string with good efficiency across universal mains input. The passive PFC approach reduces component count compared with two-stage active PFC designs, lowering cost and improving reliability in sealed ceiling fixtures where heat and accessibility matter. Analog dimming supports scene control, and the adaptive off-time control keeps switching losses managed across line and load conditions. Layout should follow the datasheet guidelines for short gate/sense loops and adequate copper for the switching components to keep junction temperatures within limits.
推薦
General Illumination Power Supplies
The LM3444 serves as the constant-current conversion stage in general illumination power supplies where a simple, efficient single-stage buck converter with passive power factor correction is preferred over a more complex two-stage design. Constant off-time control means no loop compensation design is required, shortening development time, and the architecture stays stable across the 90VAC-265VAC universal input range. Cycle-by-cycle current limiting and thermal shutdown give robust fault behavior for field-installed luminaires. The 10-VSSOP package suits compact driver boards, while the SOIC-8 option eases assembly on standard processes.
推薦
Industrial and Commercial Lighting
Industrial and commercial fixtures often must meet power quality expectations similar to IEC 61000-3-2 Class C for lighting, and the LM3444's passive PFC shaping of input current supports such targets while keeping the driver single-stage and efficient. Its wide universal-mains operation covers global installations, and the analog dimming pin enables integration with 0-10V-style dimming interfaces through simple external circuitry. Rugged protection features (thermal shutdown, cycle-by-cycle current limit) improve field reliability, and high-frequency operation reduces magnetics size for slim industrial luminaire housings.
推薦
Dimmable Task and Accent Lighting
The LM3444's analog dimming input makes it suitable for task and accent luminaires that need smooth brightness control without a microcontroller-based dimming engine. The controller adjusts LED current in response to the analog control voltage while the adaptive constant off-time loop keeps operation stable over the dimming range. High-frequency switching (up to 1 MHz) keeps magnetics small and moves switching artifacts above the audible band, avoiding acoustic noise in quiet environments. A passive PFC input stage keeps line current quality acceptable even at reduced output levels in typical residential and office circuits.
推薦
推薦產品摘要
工程參考資料，適用於 LM3444 — 比較、設計指引及合規資訊。
選型指南
與替代品比較
| 參數 | 本產品 | LM3444MM/NOPB | LM3444MX/NOPB | LM3445 |
|---|---|---|---|---|
| Package | 10-pin VSSOP or 8-lead SOIC | VSSOP-10 - same | SOIC-8 - package variant | SOIC-8 - pinout differs |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Topology | Buck, constant off-time | Buck, constant off-time | Buck, constant off-time | Buck, constant off-time + TRIAC decode |
| Dimming | Analog dimming | Analog dimming | Analog dimming | TRIAC + analog dimming |
| Power Factor Correction | Passive PFC, PF > 0.9 | Passive PFC | Passive PFC | Passive PFC |
| TRIAC Dimmer Compatibility | No | No | No | Yes |
主要差異化特點
- Adaptive constant off-time control with no loop compensation needed (對比LM3445)
- Passive PFC achieving PF > 0.9 without an active PFC controller (對比TPS92691)
- High-frequency operation up to 1 MHz (對比LM3445)
設計說明
The LM3444 handles rectified mains voltage, so switching and conduction losses concentrate in the power path. Provide adequate PCB copper area for heat dissipation as stated in the TI datasheet, and do not rely on the internal thermal shutdown for normal operation - it is a fault protection, not a cooling mechanism. Size copper pours and airflow so the junction stays well below the shutdown threshold at maximum ambient.
Keep the gate drive and current-sense loops short to minimize parasitic ringing, and place the sense resistor directly adjacent to the controller ground reference for accurate current regulation. The inductor and sense resistor choices directly affect output current accuracy and efficiency per the datasheet design equations - follow the component selection guidelines rather than generic LED driver rules of thumb.
The passive PFC circuit requires specific input-stage component values from the datasheet application section; substituting generic values degrades power factor below the >0.9 target and may affect harmonic performance. Also remember the LM3444 lacks TRIAC dimming decode - using it on a wall dimmer causes flicker; select LM3445 for dimmer-compatible designs instead.
合規資訊
NOPB suffix on LM3444MM/NOPB indicates lead-free/RoHS-compliant construction per TI and DigiKey product pages. Other compliance details not stated in provided data.
