L7981TR - 2A Step-Down Switching Regulator | STMicroelectronics
料号： L7981TR ✓ 量产中| 数量 | 单价 | 小计 |
|---|---|---|
| 1 | $1.7178 | $1.72 |
L7981TR 概述
A step-down switching regulator, also known as a buck converter, is a type of DC-DC converter that efficiently reduces a higher input voltage to a lower output voltage. Unlike linear regulators, which dissipate excess power as heat, switching regulators use an inductor and a switch to transfer energy in discrete pulses, achieving high efficiency, especially when the input-to-output voltage difference is large. The L7981TR belongs to the broader category of power management ICs, specifically within the DC-DC converter family, and is designed for applications requiring reliable and efficient voltage step-down.
Key features of the L7981TR include a 2A output current capability, a wide input voltage range of 4.5V to 28V, and a fixed 3.3V output voltage. The device operates at a switching frequency of 250 kHz, which balances efficiency and component size. It also features internal current limiting, thermal shutdown, and an enable pin for power sequencing. The SO-8 package offers a compact footprint with a thermal resistance of approximately 62.5 C/W, allowing for moderate power dissipation without external heatsinking.
The L7981TR utilizes a current-mode control architecture, which provides fast transient response and simplifies loop compensation. The integrated high-side MOSFET reduces external component count, while the internal compensation network minimizes design complexity. The device's high efficiency, typically above 85% for 12V to 3.3V conversion at 1A load, makes it suitable for battery-powered and industrial applications where power loss must be minimized.
Typical applications include point-of-load (POL) converters for microcontrollers and FPGAs, industrial control systems, and distributed power architectures. The wide input range allows operation from 5V USB supplies, 12V industrial rails, and 24V bus systems, providing design flexibility across multiple platforms.
When designing with the L7981TR, ensure proper input and output capacitor selection to maintain stability and minimize output ripple. The enable pin allows sequenced power-up in multi-rail systems, which is critical for processors requiring specific rail sequencing. Additionally, the thermal pad on the SO-8 package should be connected to a sufficient copper area for heat dissipation.
直接替换替代料： L7981TR ——相同封装，引脚兼容。需要 PCB 改动的不同封装料号已排除。
本系列中的变体
可与以下型号直接替换的同系列型号： L7981TR （相同外形与封装尺寸） ——差异在于 Enable Pin, Input Voltage Range, Maximum Output Current, Output Type, Package.
快速对比工具——选择替代料号进行并排对比：
L7981
✅ 直接替换📋 参考替代料（不在目录中）
L7986TR
✅ 直接替换 ⚠️ 规格未核验✓ 有现货
$1.85 / 个
查看数据手册 →L7987TR
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
LM2596S-3.3
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
MP1584EN
✅ 直接替换 ⚠️ 规格未核验📋 参考替代料（不在目录中）
L7981TR 最大额定值与电气特性
| 输出类型 | Fixed |
| 输出电压 | 3.3 V |
| 最大输出电流 | 2 A |
| 输入电压范围 | 4.5 V to 28 V |
| 开关频率 | 250 kHz |
| 效率 | 85% (typical, 12V to 3.3V at 1A) |
| 静态电流 | 2.5 mA |
| 热阻 | 62.5 C/W |
| 工作温度 | -40C to +150C |
| 封装 | SO-8 |
| 安装类型 | Surface Mount |
| MSL 等级 | 1 (unlimited) |
| RoHS 状态 | Compliant |
| 使能引脚 | Yes (active-high) |
| 同步整流 | No |
L7981TR 引脚配置
| 引脚 1 | BOOT — Bootstrap capacitor connection for high-side driver |
| 引脚 2 | IN — Input supply voltage |
| 引脚 3 | SW — Switch node output |
| 引脚 4 | GND — Ground |
| 引脚 5 | FB — Feedback pin (fixed 3.3V output, connect to output) |
| 引脚 6 | EN — Enable pin (active high) |
| 引脚 7 | COMP — Compensation pin (internal compensation, connect to GND) |
| 引脚 8 | VCC — Internal supply voltage (decouple with 1uF capacitor) |
典型应用
L7981TR 适用于 6 应用s: Point-of-Load (POL) Converters, Industrial Control Systems, Distributed Power Architectures, Battery-Powered Devices, Telecom and Networking Equipment, Consumer Electronics.
Point-of-Load (POL) Converters
The L7981TR is ideal for POL converters that step down a 12V or 24V bus to a 3.3V logic rail. Its 2A output current and high efficiency (85% typical) ensure reliable power delivery to microcontrollers, FPGAs, and DSPs. The fixed 3.3V output simplifies design, while the enable pin allows sequenced power-up in multi-rail systems. The wide input range (4.5V to 28V) accommodates various bus voltages, and the internal compensation reduces external component count, saving board space. In a typical POL application, the L7981TR is placed close to the load, with a 10uF input capacitor and a 22uF output capacitor to minimize ripple. The device's current-mode control provides fast transient response, essential for digital loads that draw dynamic currents. Compared to linear regulators, the switching topology dissipates less power, making it suitable for high-current, high-voltage-drop applications.
推荐
Industrial Control Systems
In industrial control systems, the L7981TR provides a stable 3.3V rail for sensors, actuators, and communication interfaces. Its wide input voltage range (4.5V to 28V) allows direct connection to 24V industrial buses, eliminating the need for intermediate conversion stages. The device's thermal shutdown and current limiting protect against overloads, enhancing system reliability. The SO-8 package with a thermal resistance of 62.5 C/W can handle moderate power dissipation without external heatsinking, making it suitable for enclosed control cabinets. The enable pin enables power sequencing in systems with multiple voltage rails, ensuring proper startup order. The high efficiency reduces heat generation, which is critical in sealed enclosures. In a typical industrial application, the L7981TR is used to power a PLC's I/O modules, with input filtering to handle transients from inductive loads.
推荐
Distributed Power Architectures
The L7981TR is well-suited for distributed power architectures where a central power supply generates an intermediate bus voltage (e.g., 12V) that is then converted to local rails. Its 2A output current and high efficiency make it an excellent choice for intermediate bus converters (IBCs) that feed multiple point-of-load regulators. The fixed 3.3V output is a common logic voltage, and the device's small SO-8 package allows dense board layouts. The wide input range ensures compatibility with various bus voltages, and the internal compensation simplifies design. In a distributed power system, the L7981TR can be used to generate a 3.3V rail for digital logic, while other converters handle 5V and 1.8V rails. The enable pin allows coordinated startup, preventing inrush current issues. The device's current-mode control provides good line and load regulation, essential for maintaining stable voltages across the system.
推荐
Battery-Powered Devices
The L7981TR is an excellent choice for battery-powered devices that require efficient step-down conversion from a battery voltage (e.g., 12V Li-ion pack) to a 3.3V logic rail. Its high efficiency (85% typical) extends battery life, and the low quiescent current of 2.5 mA minimizes standby power consumption. The wide input voltage range accommodates battery voltage variations during discharge. The enable pin allows the device to be shut down when the system is idle, further conserving power. In a typical battery-powered application, the L7981TR is used to power a microcontroller and sensors, with a low-dropout regulator (LDO) for analog circuits that require ultra-low noise. The switching regulator's efficiency reduces heat generation, which is important in portable devices with limited thermal dissipation. The SO-8 package is compact, fitting into space-constrained designs.
推荐
Telecom and Networking Equipment
In telecom and networking equipment, the L7981TR provides a reliable 3.3V rail for line cards, switches, and routers. Its wide input range (4.5V to 28V) allows operation from standard telecom voltages like -48V (with appropriate front-end conversion) or 12V intermediate rails. The device's high efficiency reduces power dissipation, which is critical in densely packed equipment racks. The enable pin enables power sequencing in systems with multiple voltage rails, ensuring proper startup order. The internal compensation simplifies design, and the SO-8 package is suitable for high-density PCBs. In a typical networking application, the L7981TR powers a switch ASIC and PHY transceivers, with input filtering to meet EMC requirements. The device's current-mode control provides fast transient response, essential for handling bursty network traffic.
推荐
Consumer Electronics
The L7981TR is used in consumer electronics such as set-top boxes, gaming consoles, and smart home devices to generate a 3.3V rail from a 12V or 5V supply. Its small SO-8 package and high efficiency make it ideal for compact, energy-efficient designs. The fixed 3.3V output is a common logic voltage, and the device's low quiescent current helps meet energy star requirements. The enable pin allows the device to be shut down in standby mode, reducing power consumption. In a typical consumer application, the L7981TR powers a system-on-chip (SoC) and memory, with a 10uH inductor and 22uF output capacitor for stable operation. The device's internal compensation reduces external component count, lowering BOM cost. The wide input range provides design flexibility across different product lines.
推荐
推荐产品汇总
工程参考数据： L7981TR ——对比、设计指导和合规信息。
选型指南
与替代料对比
| 参数 | 本产品 | L7981 | L7986TR | L7987TR | LM2596S-3.3 | MP1584EN |
|---|---|---|---|---|---|---|
| Package | SO-8 | SO-8 - same | SO-8 - same | SO-8 - same | SO-8 - same | SO-8 - same |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics | Texas Instruments | Monolithic Power Systems |
| Output Voltage | 3.3V (fixed) | 3.3V (fixed) | 3.3V (fixed) | Adjustable | 3.3V (fixed) | Adjustable |
| Output Current | 2A | 2A | 3A | 2A | 3A | 3A |
| Input Voltage Range | 4.5V to 28V | 4.5V to 28V | 4.5V to 28V | 4.5V to 28V | 4.5V to 40V | 4.5V to 28V |
| Switching Frequency | 250 kHz | 250 kHz | 250 kHz | 250 kHz | 150 kHz | 1.5 MHz |
| Enable Pin | Yes (active-high) | Yes (active-high) | Yes (active-high) | Yes (active-high) | No | Yes (active-high) |
| Internal Compensation | Yes | Yes | Yes | Yes | No | Yes |
关键差异点
- Internal compensation simplifies design （对比 LM2596S-3.3)
- Enable pin for power sequencing （对比 LM2596S-3.3)
- Higher switching frequency reduces component size （对比 LM2596S-3.3)
设计说明
Place the input capacitor (10uF ceramic) as close as possible to the IN pin (pin 2) and GND pin (pin 4) to minimize input ripple and reduce EMI. The output capacitor (22uF ceramic) should be placed near the SW pin (pin 3) and GND. Use a solid ground plane to minimize parasitic inductance. The bootstrap capacitor (100nF) should be connected between BOOT (pin 1) and SW (pin 3) with minimal trace length.
The SO-8 package has a thermal resistance of 62.5 C/W. For a 12V to 3.3V conversion at 2A, power dissipation is approximately (12V - 3.3V) * 2A * (1 - efficiency) = 8.7W * 0.15 = 1.3W, resulting in a temperature rise of 81C above ambient. Ensure adequate copper area on the PCB to dissipate heat, or reduce output current if ambient temperature is high.
Do not exceed the absolute maximum input voltage of 28V. Ensure the enable pin is not left floating; tie it to VIN if not used. The COMP pin (pin 7) should be connected to GND with a small capacitor (e.g., 1nF) for stability, as the device has internal compensation. Use a Schottky diode for the catch diode to minimize switching losses.
合规信息
RoHS compliant per STMicroelectronics product page. Not AEC-Q100 qualified. Lead-free finish.
