LM3481MMX/NOPB - 2.97-48V Boost/SEPIC/Flyback Controller | TI
MPN： LM3481MMX/NOPB ✓ 啟用中LM3481MMX/NOPB 概覽
A DC-DC switching controller is an integrated circuit that manages the power conversion process by controlling external power switches (typically MOSFETs) to regulate output voltage or current. Unlike linear regulators, switching controllers offer high efficiency, especially when there is a large difference between input and output voltages. The LM3481 belongs to the family of current-mode PWM controllers, which provide robust line and load regulation and simplified loop compensation. This controller is part of the broader category of power management ICs, essential for modern electronic systems.
Key features of the LM3481MMX/NOPB include current-mode PWM control, a wide input voltage range, and an adjustable switching frequency up to 1MHz. It also features a built-in soft-start, cycle-by-cycle current limiting, and thermal shutdown protection. The device can drive an external N-channel MOSFET, enabling high-current applications that would be impractical with integrated-switch regulators. Its low quiescent current and high efficiency make it ideal for battery-powered and energy-conscious designs.
Technically, the LM3481 uses a current-mode control architecture, which provides inherent feed-forward compensation and simplifies the design of the feedback loop. The controller includes a precision reference, error amplifier, and PWM comparator. It also offers a shutdown pin for power sequencing and a frequency synchronization pin for noise-sensitive systems. The device is specified for operation over the industrial temperature range of -40C to 125C, ensuring reliability in harsh environments.
Typical applications include automotive power supplies, industrial power systems, LED drivers, and battery chargers. The wide input range and ability to implement boost, SEPIC, and flyback topologies make it a versatile choice for designers.
When designing with the LM3481, careful attention must be paid to the external MOSFET selection, inductor sizing, and loop compensation to ensure stable operation across all load conditions. The datasheet provides detailed design equations and application circuits to guide the designer.
直接替換替代品，適用於 LM3481MMX/NOPB — 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。
此系列的變體
與下列產品可直接替換的同系列型號： LM3481MMX/NOPB （相同外形與佔位） — 差異在於 Package, RoHS Status, Topology.
LM3481QMMX/NOPBQ1
✅ 直接替換聯絡詢價
查看資料表 →LM3481MM/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LM3478MMX/NOPB
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
LM3481MMX/NOPB 最大額定值與電氣特性
| 拓撲 | Boost, Flyback, SEPIC |
| Control Method | Current Mode PWM |
| 輸入電壓範圍 | 2.97 V to 48 V |
| 輸出數量 | 1 |
| 切換頻率 | Adjustable up to 1 MHz |
| Maximum Duty Cycle | 85% |
| Output Switch Driver | External low-side N-channel MOSFET |
| 功能特色 | Soft-start, cycle-by-cycle current limit, thermal shutdown, shutdown pin, freq sync |
| 工作溫度 | -40C to +125C |
| 封裝 | VSSOP-10 (DGS) |
| Package Description | 10-TFSOP, 10-MSOP, 3.00 mm width |
| 安裝類型 | Surface Mount |
| Packaging | Tape & Reel (TR) |
| Supplier Device Package | 10-VSSOP |
| RoHS 狀態 | Compliant (NOPB - no Pb) |
| PWM Type | Current Mode |
LM3481MMX/NOPB 腳位配置
| 腳位 1 | AGND — Analog ground reference |
| 腳位 2 | VIN — Input supply, 2.97V to 48V |
| 腳位 3 | ISENSE — Current sense input for cycle-by-cycle current limit |
| 腳位 4 | FREQ — Frequency set / synchronization pin |
| 腳位 5 | SS — Soft-start programming capacitor |
| 腳位 6 | COMP — Error amplifier output for loop compensation |
| 腳位 7 | FB — Feedback input from output divider (1.26V ref) |
| 腳位 8 | SHUTDOWN — Shutdown and standby control pin |
| 腳位 9 | PGND — Power ground for gate driver |
| 腳位 10 | OUT — Gate drive output to external N-channel MOSFET |
典型應用
LM3481MMX/NOPB 適用於 6 應用s: Automotive Power Supplies, Industrial Power Systems, LED Drivers, Battery-Powered Portable Devices, Battery Chargers, RF and Noise-Sensitive Rails.
Automotive Power Supplies
The LM3481 fits automotive 12V/24V rail conditioning where input transients demand wide headroom: its 2.97V-48V input range tolerates load-dump-adjacent conditions, and the AEC-Q100 LM3481QMMX/NOPBQ1 variant covers temperature grade requirements. In a boost configuration it steps battery voltage up to regulated 5V/12V rails for ECUs and infotainment. Cycle-by-cycle current limiting and thermal shutdown provide fault protection. Designers should add input TVS protection and verify duty cycle margin, as the 85% maximum limits very high step-up ratios at low battery voltage.
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Industrial Power Systems
Industrial PLC and instrumentation boards often combine 24V backplanes with low-voltage logic, and the LM3481 bridges this efficiently in SEPIC or flyback configurations. The 48V maximum input covers nominal 24V rails with margin, while 1 MHz operation shrinks magnetics for dense DIN-rail modules. Current-mode control provides fast transient response for motor-control and I/O subsystems. Layout discipline is essential: keep the power loop short and route the ISENSE line kelvin-connected to minimize switching noise in the current-limit threshold.
推薦
LED Drivers
Constant-current LED strings benefit from the LM3481's current-mode architecture: sensing LED current on the FB pin enables accurate regulation, while up to 1 MHz switching allows small inductors in slim luminaire form factors. Boost topology powers long LED strings above the input rail; SEPIC handles dimming input from partially charged batteries. With 48V input capability, high-brightness strings on 24V industrial lighting buses are practical. The shutdown pin supports PWM dimming interfaces, and soft-start prevents current overshoot during lamp ignition.
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Battery-Powered Portable Devices
For single-cell Li-ion (2.97V-4.2V) or multi-cell alkaline products, the LM3481's low startup input of 2.97V and high efficiency preserve battery life while generating 5V or 12V rails for displays, sensors, and RF modules. The adjustable frequency feature lets designers trade efficiency against magnetic size, and low quiescent consumption plus shutdown pin enable low standby drain. Because the controller drives an external MOSFET, output power scales with the selected switch rather than a fixed internal limit, making one controller reusable across a product family.
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Battery Chargers
Charger front ends require wide input tolerance and robust current control, both core LM3481 strengths. Implementing a SEPIC converter allows charging from sources above, below, or equal to the battery voltage - useful for USB, solar-panel, and vehicle inputs feeding 3-4 cell packs. Cycle-by-cycle current limiting doubles as fast-charge current control when the FB loop regulates sensed current. The 48V input ceiling supports 48V telecom charging stacks. Designers must verify inductor saturation at peak switch currents and provide a well-damped compensation network for stable CC/CV transitions.
推薦
RF and Noise-Sensitive Rails
RF front-end and PLL/VCO supplies benefit from the LM3481's frequency synchronization pin, which locks switching operation to a system clock and moves switching spurs to a predictable, filterable spectral location. Boost or SEPIC stages generate clean 5V or negative-bias-class rails from 12V/24V backplanes, followed by an LDO such as the TPS7A family for final noise filtering. Keeping the switching frequency above 500 kHz places ripple where ferrite filtering is most effective, and current-mode control simplifies compensation across RF load transients.
推薦
推薦產品摘要
工程參考資料，適用於 LM3481MMX/NOPB — 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 | LM3481QMMX/NOPBQ1 | LM3481MM/NOPB | LM3478MMX/NOPB | LM5117PMH/NOPB |
|---|---|---|---|---|---|
| Package | VSSOP-10 (DGS) | VSSOP-10 (DGS) - same | VSSOP-10 (DGS) - same | VSSOP-10 (DGS) - same | TSSOP-16 (PWP) - different |
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Input Voltage Range | 2.97V to 48V | 2.97V to 48V | 2.97V to 48V | 2.97V to ~40V | 5.5V to 65V |
| Switching Frequency | Adjustable up to 1 MHz | Adjustable up to 1 MHz | Adjustable up to 1 MHz | Adjustable up to 1 MHz | Adjustable up to 750 kHz |
| Control Method | Current Mode PWM | Current Mode PWM | Current Mode PWM | Current Mode PWM | Peak Current Mode (EMI-tolerant) |
| Topologies | Boost, Flyback, SEPIC | Boost, Flyback, SEPIC | Boost, Flyback, SEPIC | Boost, Flyback, SEPIC | Boost, Flyback, SEPIC, Buck-Boost |
| Temperature Range | -40C to +125C | -40C to +125C (AEC-Q100) | -40C to +125C | -40C to +125C | -40C to +125C |
| Pin Compatibility | Reference (VSSOP-10) | Pin-to-pin drop-in | Pin-to-pin drop-in | Pin-to-pin compatible | Not pin compatible |
主要差異化特點
- 48V maximum input in tiny VSSOP-10 (對比LM3478MMX/NOPB)
- Automotive qualified drop-in available (對比LM3481QMMX/NOPBQ1)
- External MOSFET scales output power (對比LM5117PMH/NOPB)
設計說明
Keep the power loop (input capacitor, MOSFET, inductor/transformer primary, sense resistor) as short as possible to minimize switching ringing and EMI. Connect the ISENSE pin to the sense resistor using a Kelvin trace that does not share the power ground path. Place the FREQ resistor and COMP network close to the IC on a quiet analog ground island tied to AGND.
Select the external MOSFET for Vds rating above peak switching node voltage (output voltage plus flyback spikes), and verify Rds(on) at the controller gate-drive level. The 85% maximum duty cycle limits very high boost ratios at low input - compute D = 1 - VIN/VOUT at minimum input and confirm margin. Size the current sense resistor for cycle-by-cycle limit below inductor saturation current.
Do not omit the SS soft-start capacitor - without it, inrush at startup can trip the current limit and cause hiccup behavior. When using the frequency sync function, ensure the synchronization pulse conforms to datasheet timing. For deep shutdown, drive the SHUTDOWN pin below the datasheet threshold; floating it can leave the part in an indeterminate state.
合規資訊
NOPB suffix denotes No-Pb lead-free TI offering. For automotive AEC-Q100 qualification, use LM3481QMMX/NOPBQ1. Halogen-free and conflict minerals status not confirmed in provided data.
