LM2676S-ADJ/NOPB - 3A Step-Down Switching Regulator | Texas Instruments
MPN： LM2676S-ADJ/NOPB ✓ 啟用中LM2676S-ADJ/NOPB 概覽
A buck (step-down) switching regulator is a power-management IC that converts a higher DC input voltage to a lower DC output voltage by alternately storing energy in an inductor and releasing it to the load through a MOSFET switch. Within the system hierarchy, the LM2676 belongs to the SIMPLE SWITCHER family of non-isolated buck regulators, which sit within DC-DC switching regulators, which themselves are a sub-category of power-management ICs (PMICs). Compared with linear regulators (LDOs), buck converters like the LM2676 trade higher efficiency (typically 75-90%) for added complexity (inductor, catch diode, input/output capacitors) and produce switching ripple that must be filtered.
Key features include a fixed 260 kHz switching frequency that allows use of small magnetic components, an internal DMOS power switch rated for 45V, a low quiescent current of 4.2 mA in standby, thermal shutdown, current limit, and an on/off enable control. The TO-263-7K-T package has a low thermal resistance (junction-to-case) of approximately 2 C/W, enabling full-power operation with a small copper heatsink area or none at all in low-duty applications.
The device uses TI's classic buck control topology with voltage-mode control and internal compensation, simplifying external component selection. The feedback pin uses an external resistor network, while a soft-start capacitor controls soft-start discharge to limit inrush current during power-up. The high-side DMOS switch achieves low Rds(on) for high efficiency at 3A loads, making the LM2676S-ADJ/NOPB well-suited for medium-power point-of-load conversion.
Typical applications include industrial 24V bus regulation, automotive accessory power (post-transient protection), battery-powered equipment, distributed 5V/12V/15V/24V rails in instrumentation, point-of-load regulation downstream of a rectifier, and high-current single-rail or front-end conversion. The wide input-to-output ratio and 3A capability cover most moderate-power distributed-power requirements.
Design considerations: the catch diode with current limiting must be a Schottky type rated for the input voltage (e.g., 40V+ SS34), the inductor is typically 22-33 µH for most VIN/VOUT combinations, and the feedback divider must use 1% resistors. Because the LM2676 is not pin-compatible with newer TI WEBENCH-optimized regulators like the LMR33630, redesigns may be required for footprint migration, though the simple external BOM is widely documented and supported.
直接替換替代品，適用於 LM2676S-ADJ/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： LM2676S-ADJ/NOPB （相同外形與佔位） — 差異在於 Output Voltage Range, Package, Topology.
LM2676SX-ADJ/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LM2676S-ADJ/NOPB
✅ 直接替換聯絡詢價
查看資料表 →LM2678S-ADJ/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LM2673S-ADJ/NOPB
✅ 直接替換聯絡詢價
查看資料表 →LM2675S-ADJ/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LM2676T-ADJ/NOPB
✅ 直接替換📋 參考替代品（不在目錄中）
LM2676S-ADJ/NOPB 最大額定值與電氣特性
| 拓撲 | Buck (Step-Down) |
| 輸入電壓範圍 | 8 V to 40 V |
| 輸出電壓範圍 | 1.2 V to 37 V (Adjustable) |
| Output Current | 3 A |
| 輸出數量 | 1 |
| 切換頻率 | 260 kHz (typical) |
| 靜態電流 | 4.2 mA (typical) |
| 輸出類型 | Adjustable |
| 同步整流器 | No |
| 效率 | 75-90% (typical, application dependent) |
| 工作溫度範圍 | -40 C to +125 C |
| 封裝 | TO-263-7 (D2PAK, 7 Leads + Tab, KTW) |
| 安裝類型 | Surface Mount |
| RoHS 狀態 | Compliant (Pb-free / NOPB suffix) |
| Lead-Free Finish | Yes (NOPB) |
LM2676S-ADJ/NOPB 腳位配置
| 腳位 1 | VIN — Input supply voltage (8V to 40V) |
| 腳位 2 | SW — Switch node (internal DMOS drain) - connect to external inductor and Schottky catch diode |
| 腳位 3 | GND — Ground |
| 腳位 4 | FB — Feedback input - set VOUT with external resistor divider |
| 腳位 5 | NC — Not connected (per datasheet) |
| 腳位 6 | SS — Soft-start - external capacitor controls soft-start time |
| 腳位 7 | ON/OFF — Enable input (active-high) |
| 腳位 TAB | GND/Tab — Exposed thermal pad (electrically GND) - primary thermal dissipation path |
典型應用
LM2676S-ADJ/NOPB 適用於 6 應用s: Industrial 24V Bus Point-of-Load Regulation, Automotive 12V Accessory Power, Distributed 5V/12V Rails in Instrumentation, Battery-Powered Equipment, Power Supply Replacement / Linear Regulator Replacement, High-Current Single-Rail Conversion.
Industrial 24V Bus Point-of-Load Regulation
The LM2676S-ADJ/NOPB converts a 24V industrial bus (18-32V typical) to lower voltages such as 5V, 12V, or 15V for PLCs, motor drivers, and industrial sensor subsystems. With 8V-40V input tolerance, 3A load handling, and 75-90% efficiency, the regulator handles moderate-load point-of-load conversion without complex compensation networks. Unlike smaller-current LM2674/LM2675, the LM2676's 3A capability supports multi-rail distribution downstream.
推薦
Automotive 12V Accessory Power
The LM2676S-ADJ/NOPB regulates the 12V automotive bus (8V-18V typical) down to accessory voltages such as 5V or 8V for body-control modules, infotainment subsystems, and aftermarket electronics. The 40V input tolerance handles jump-start events, while the 8V minimum covers cold-crank scenarios. Unlike LDO-based designs that would dissipate 7W at 12V-to-5V/3A, the LM2676's 75-85% efficiency dramatically reduces thermal load.
推薦
Distributed 5V/12V Rails in Instrumentation
The LM2676S-ADJ/NOPB generates 5V or 12V rails in bench-top and rack-mount instrumentation. With 3A continuous load, the part supports digital subsystems (FPGA/CPLD rails, MCU rails) and analog signal chains requiring well-regulated supplies. The 260 kHz fixed switching frequency avoids interference with sensitive analog measurements and supports small inductors. Unlike a complex synchronous buck, the LM2676's simple non-synchronous BOM keeps the bill of materials short.
推薦
Battery-Powered Equipment
The LM2676S-ADJ/NOPB regulates battery stacks (multi-cell Li-ion, lead-acid, or 4-6 cell NiMH packs) down to logic or analog supply voltages for portable instruments and field equipment. The 4.2 mA quiescent current and high efficiency extend battery life, and the wide 1.2V-37V output range covers most battery-powered system voltages. Unlike a latched power path, the LM2676's on/off enable pin supports load-disconnect switching for power management.
推薦
Power Supply Replacement / Linear Regulator Replacement
The LM2676S-ADJ/NOPB replaces legacy linear regulators (LM317/78xx) where high dropout dissipation makes linear regulators impractical, while keeping the same adjustable pinout voltage range (1.2V-37V). At 12V-to-5V/3A, an LDO would dissipate 21W — the LM2676 dissipates roughly 3W at 80% efficiency, reducing heatsink requirements and enabling smaller PCB area. The TO-263-7 footprint is compatible with LM7805/LM317 thermal layouts.
推薦
High-Current Single-Rail Conversion
The LM2676S-ADJ/NOPB delivers 3A at a single regulated output for moderate-power applications such as 5V/12V solenoid drivers, LED drivers, or motor-driver auxiliary rails. The internal DMOS switch eliminates the external MOSFET, simplifying layout. The TO-263-7 exposed tab provides direct thermal path to PCB copper, supporting 3A continuous without an external heatsink in well-designed boards with sufficient copper area.
推薦
推薦產品摘要
工程參考資料，適用於 LM2676S-ADJ/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 | LM2676SX-ADJ/NOPB | LM2678S-ADJ/NOPB | LM2673S-ADJ/NOPB | LM2675S-ADJ/NOPB | LM2676T-ADJ/NOPB |
|---|---|---|---|---|---|---|
| Brand | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments | Texas Instruments |
| Package | TO-263-7 (D2PAK, KTW) | TO-263-7 (KTW) - same | TO-263-7 (KTW) - same | TO-263-7 (KTW) - same | TO-263-7 (KTW) - same | TO-220-7 (Formed Leads) - through-hole |
| Input Voltage Range | 8V to 40V | 8V to 40V | 8V to 40V | 8V to 40V | 8V to 40V | 8V to 40V |
| Output Current | 3A | 3A | 5A | 3A | 1A | 3A |
| Output Voltage Range | 1.2V to 37V (Adjustable) | 1.2V to 37V (Adjustable) | 1.2V to 37V (Adjustable) | 1.2V to 37V (Adjustable) | 1.2V to 37V (Adjustable) | 1.2V to 37V (Adjustable) |
| Switching Frequency | 260 kHz | 260 kHz | 260 kHz | 260 kHz | 260 kHz | 260 kHz |
| Soft-Start Pin | Yes | Yes | Yes | Yes (current-limit pin also) | Yes | Yes |
| Mounting Type | Surface Mount (TO-263-7) | Surface Mount (TO-263-7) | Surface Mount (TO-263-7) | Surface Mount (TO-263-7) | Surface Mount (TO-263-7) | Through-Hole (TO-220-7) |
| Pb-Free / RoHS | Yes (NOPB) | Yes (NOPB) | Yes (NOPB) | Yes (NOPB) | Yes (NOPB) | Yes (NOPB) |
主要差異化特點
- Internal DMOS switch eliminates external MOSFET (對比LM2676T-ADJ/NOPB (through-hole variant))
- 3A continuous load current in TO-263-7 (對比LM2675S-ADJ/NOPB (1A))
- 5A upgrade available in same TO-263-7 footprint (對比LM2678S-ADJ/NOPB)
設計說明
Estimated: at VIN=24V, VOUT=5V, IOUT=3A, the LM2676S-ADJ/NOPB dissipates approximately (24V-5V)*3A*((1/efficiency)-1) ≈ 9.5W at 80% efficiency. The TO-263-7 package has theta_JC of roughly 2 C/W and theta_JA of 40-50 C/W on 1 sq inch of 1-oz PCB copper. Junction temperature rise above ambient is approximately 9.5W * 45 C/W ≈ 428 C — well above the 125 C maximum. A heatsink, larger copper area (>= 4 sq inches), or forced airflow is required for continuous 3A operation above 50% duty cycle.
Use wide PCB traces for VIN, SW, and GND paths to minimize voltage spikes and EMI. Place input ceramic capacitor (>= 22 µF low-ESR) as close as possible to the VIN pin and PGND (exposed tab). The SW node trace should be kept short and routed directly to the inductor to reduce radiated EMI from the high-dV/dt switching waveform. Output ceramic or low-ESR electrolytic capacitor (>= 68 µF) must be placed close to the inductor output. Use a single ground plane with the catch diode and output capacitor return paths connected directly to the IC exposed tab.
Do not use a Schottky catch diode below 30V rating — common transient SS34 (40V) or SS36 (60V) is required for 40V input. The feedback resistor divider must use 1% tolerance resistors; with 5% resistors the output voltage can deviate more than 5% from nominal. The inductor saturation current must exceed the peak switch current (typically 4-5A for a 3A design at high load transients). The soft-start capacitor (typically 0.1 µF) controls startup inrush — do not omit it, or the input supply may dip below undervoltage lockout during power-up. Never exceed 45V on VIN or VIN transients — the internal DMOS is rated 45V absolute maximum.
合規資訊
RoHS compliant and Pb-free per NOPB suffix. Not AEC-Q100 qualified; for AEC-Q100 automotive applications consider LM2676-Q1 variants if available, or newer TI automotive-grade regulators. Halogen-free status not explicitly stated in the verified data.
