L7985TR - 2A Step-Down Switching Regulator | STMicroelectronics
MPN： L7985TR ✓ 啟用中L7985TR 概覽
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 a controlled manner, achieving high efficiency. The L7985TR belongs to the family of voltage regulators, which are essential components in power management systems, converting unregulated power sources into stable, usable voltages for electronic circuits.
Key features of the L7985TR include a 250 kHz fixed switching frequency, an internal power MOSFET, and a current-mode control architecture. The device offers a typical efficiency of over 85% at full load, reducing power loss and heat generation. It also includes a built-in soft-start function to limit inrush current during startup, and a thermal shutdown protection to prevent damage from overheating. The output voltage is adjustable from 0.6V to the input voltage, providing flexibility for various design requirements.
The L7985TR utilizes a current-mode control scheme, which provides fast transient response and simplifies loop compensation. The internal power switch is rated for a peak current of 3A, ensuring reliable operation under load transients. The device also features a low quiescent current of 2.5 mA, which is beneficial for battery-powered applications. The HSOP-8 package has a thermal resistance of 40°C/W, allowing for efficient heat dissipation in moderate power applications.
Typical applications for the L7985TR include point-of-load converters, distributed power systems, industrial control systems, and automotive power supplies. Its wide input voltage range and high efficiency make it ideal for converting 12V or 24V bus voltages to lower logic rails. The device is also suitable for LED lighting applications, where constant current regulation is required.
When designing with the L7985TR, it is important to select the appropriate inductor and output capacitor values to ensure stable operation. The datasheet provides a detailed design procedure and recommended component values for various output voltages and currents. Additionally, proper PCB layout is critical to minimize parasitic inductance and ensure reliable performance.
直接替換替代品，適用於 L7985TR — 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： L7985TR （相同外形與佔位） — 差異在於 Input Voltage Range, Maximum Output Current, Output Voltage Range, Package, Switching Frequency.
L7985
✅ 直接替換📋 參考替代品（不在目錄中）
L7986TR
✅ 直接替換 ⚠️ 規格未經驗證聯絡詢價
查看資料表 →L7987
✅ 直接替換 ⚠️ 規格未經驗證聯絡詢價
查看資料表 →TPS5420
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
NCP3063
✅ 直接替換 ⚠️ 規格未經驗證📋 參考替代品（不在目錄中）
L7985TR 最大額定值與電氣特性
| 輸出類型 | Adjustable |
| 輸出電壓範圍 | 0.6 V to 38 V |
| 最大輸出電流 | 2 A |
| 輸入電壓範圍 | 4.5 V to 38 V |
| 切換頻率 | 250 kHz |
| 效率 | >85% at full load |
| 靜態電流 | 2.5 mA |
| Internal Power MOSFET | Yes, 3A peak current |
| Control Architecture | Current-mode |
| 軟啟動 | Built-in |
| 過熱關機 | Yes |
| 工作溫度 | -40°C to +150°C |
| 封裝 | HSOP-8 |
| 安裝類型 | Surface Mount |
| RoHS 狀態 | Compliant |
L7985TR 腳位配置
| 腳位 1 | BOOT — Bootstrap capacitor connection for high-side driver |
| 腳位 2 | IN — Input supply voltage |
| 腳位 3 | SW — Switch node output |
| 腳位 4 | GND — Ground |
| 腳位 5 | FB — Feedback voltage sense |
| 腳位 6 | COMP — Compensation network connection |
| 腳位 7 | EN — Enable input (active high) |
| 腳位 8 | VCC — Internal supply voltage (decouple with capacitor) |
典型應用
L7985TR 適用於 6 應用s: Point-of-Load Converters, Industrial Control Systems, Automotive Power Supplies, LED Lighting, Distributed Power Systems, Battery-Powered Devices.
Point-of-Load Converters
The L7985TR is ideal for point-of-load (POL) converters that step down a higher voltage bus to a lower logic rail. Its wide input range (4.5V to 38V) and 2A output current make it suitable for powering FPGAs, microcontrollers, and other digital ICs. The high efficiency reduces heat generation, allowing for compact designs without heatsinks. In a typical POL application, the L7985TR is placed close to the load, with input and output capacitors to filter noise. The adjustable output voltage allows for precise regulation, and the current-mode control provides fast transient response to sudden load changes. Compared to linear regulators, the switching topology minimizes power loss, especially when the input-to-output voltage difference is large.
推薦
Industrial Control Systems
In industrial control systems, the L7985TR can convert a 24V DC bus to lower voltages for sensors, actuators, and control logic. Its wide input voltage range and robust thermal performance make it suitable for harsh environments. The device's thermal shutdown protection ensures safe operation under overload conditions. The fixed 250 kHz switching frequency allows for simple EMI filtering, which is important in industrial settings with strict electromagnetic compatibility requirements. The L7985TR's current-mode control provides stable operation with ceramic output capacitors, reducing the need for bulky electrolytic capacitors. This makes the design compact and reliable for long-term operation in factory automation and process control equipment.
推薦
Automotive Power Supplies
The L7985TR is well-suited for automotive power supplies, where input voltage can vary from 9V to 16V (or higher during load dump). Its input range of 4.5V to 38V provides ample margin for such transients. The device's operating temperature range of -40°C to +150°C meets automotive requirements. In a typical automotive application, the L7985TR steps down the battery voltage to power infotainment systems, sensors, or ECUs. The high efficiency reduces power dissipation, which is critical in the confined spaces of a vehicle. The built-in soft-start prevents inrush current during startup, protecting the battery and other components. The thermal shutdown feature ensures the device survives extreme conditions.
推薦
LED Lighting
The L7985TR can be used in LED lighting applications as a constant current source. By configuring the feedback network, the device regulates the output current to drive LEDs with consistent brightness. The adjustable output voltage allows for series LED strings of varying lengths. The high efficiency minimizes heat generation, which is beneficial for LED luminaires where thermal management is challenging. The current-mode control ensures stable current regulation even with input voltage variations. In a typical LED driver circuit, the L7985TR is used with an inductor and a sense resistor to set the output current. The device's wide input range makes it suitable for both low-voltage (12V) and high-voltage (24V) lighting systems.
推薦
Distributed Power Systems
In distributed power systems, the L7985TR is used to generate multiple voltage rails from a single input source. Its adjustable output voltage and 2A current capability make it versatile for various loads. The device's high efficiency reduces overall power loss in the system, improving energy efficiency. The compact HSOP-8 package allows for high power density on the PCB. In a typical distributed power architecture, the L7985TR is used as a secondary stage, converting an intermediate bus voltage (e.g., 12V) to lower logic rails (e.g., 3.3V, 5V). The current-mode control provides excellent line and load regulation, ensuring stable voltages for sensitive electronics.
推薦
Battery-Powered Devices
The L7985TR is suitable for battery-powered devices where efficiency is critical to extend battery life. Its low quiescent current of 2.5 mA helps minimize standby power consumption. The wide input voltage range allows the device to operate from a variety of battery configurations, such as 2-cell Li-ion (7.4V) or 4-cell NiMH (4.8V). The high efficiency ensures that most of the battery energy is converted to useful output, reducing heat and prolonging runtime. In a typical battery-powered application, the L7985TR steps down the battery voltage to power a microcontroller, sensors, or wireless transceiver. The soft-start feature prevents inrush current that could otherwise stress the battery.
推薦
推薦產品摘要
工程參考資料，適用於 L7985TR — 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 | L7985 | L7986 | L7987 | TPS5420 | NCP3063 |
|---|---|---|---|---|---|---|
| Package | HSOP-8 | HSOP-8 | HSOP-8 | HSOP-8 | HSOP-8 | HSOP-8 |
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics | Texas Instruments | onsemi |
| Input Voltage Range | 4.5V to 38V | 4.5V to 38V | 4.5V to 38V | 4.5V to 38V | 5.5V to 36V | 3V to 40V |
| Output Current | 2A | 2A | 3A | 1A | 2A | 1.5A |
| Switching Frequency | 250 kHz | 250 kHz | 250 kHz | 250 kHz | 500 kHz | 150 kHz |
| Output Voltage Range | 0.6V to 38V | 0.6V to 38V | 0.6V to 38V | 0.6V to 38V | 1.22V to 36V | 1.25V to 40V |
| Quiescent Current | 2.5 mA | 2.5 mA | 2.5 mA | 2.5 mA | 2 mA | 2.5 mA |
| Enable Pin | Yes | Yes | Yes | Yes | Yes | No |
主要差異化特點
- Wide input voltage range up to 38V (對比TPS5420)
- Higher output current than L7987 (對比L7987)
- Enable pin for power sequencing (對比NCP3063)
設計說明
For optimal performance, place the input capacitor (10uF) and output capacitor (22uF) as close as possible to the L7985TR pins. Use a solid ground plane to minimize parasitic inductance. The bootstrap capacitor (100nF) should be placed between BOOT and SW pins with minimal trace length. Refer to the ST application note AN2823 for layout guidelines.
The HSOP-8 package has a thermal resistance of 40°C/W (theta_JA). At 2A output with a 12V to 5V conversion, power dissipation is approximately 14W, which would cause a junction temperature rise of 560°C. This is not feasible without a heatsink. For such high power, consider using a larger package or reducing the output current. For typical applications with lower power dissipation (e.g., 12V to 5V at 1A, dissipation ~7W), a copper pour of at least 1 square inch is recommended.
Do not operate the L7985TR without a proper compensation network on the COMP pin. Use the values recommended in the datasheet for the desired output voltage and current. Also, ensure the EN pin is not left floating; tie it to VIN for always-on operation or use a logic signal for control. Incorrect inductor selection can cause instability or excessive ripple.
合規資訊
RoHS compliant per STMicroelectronics product page. Not AEC-Q100 qualified, but suitable for automotive applications per datasheet.
