ST1S40PUR - 3A, 4V to 18V Step-Down Converter | STMicroelectronics
MPN： ST1S40PUR ✓ 啟用中ST1S40PUR 概覽
A step-down (buck) converter is a type of DC-DC switching regulator that steps down an input voltage to a lower output voltage with high efficiency. Unlike linear regulators, which dissipate excess power as heat, buck converters use an inductor and switching elements to transfer energy in discrete packets, achieving efficiencies often above 85%. In the power management hierarchy, a buck converter is a type of switching regulator, which is a subset of voltage regulators, which in turn are part of power management ICs (PMICs) used in virtually all electronic systems to provide stable, efficient power rails.
Key features of the ST1S40PUR include a fixed 1.5MHz switching frequency, which allows the use of small external components (inductor and capacitors), reducing PCB footprint. The device offers a low quiescent current of 1.5mA in light-load operation, and a shutdown mode that reduces current consumption to less than 1uA. Protection features include overcurrent protection (OCP), thermal shutdown, and under-voltage lockout (UVLO). The DFN6 package (3mm x 3mm) has a thermal resistance of 45°C/W, enabling efficient heat dissipation in compact designs.
The ST1S40PUR uses a current-mode control architecture with internal compensation, simplifying the design process. The high switching frequency minimizes the size of the output inductor (typically 2.2uH to 4.7uH) and output capacitors, making it ideal for space-constrained applications. The device also features a soft-start function to limit inrush current during startup, and an enable pin for power sequencing.
Typical applications include distributed power systems, set-top boxes, LCD TVs, networking equipment, and industrial control systems. The wide input range and high output current make it suitable for powering FPGAs, DSPs, and microprocessors from 12V or 5V rails. In set-top boxes, the ST1S40PUR efficiently converts a 12V input to a 3.3V or 1.8V rail for core logic, reducing heat and improving reliability.
When designing with the ST1S40PUR, ensure proper PCB layout with short, wide traces for high-current paths and a solid ground plane. Place the input capacitor close to the VIN pin and the output inductor close to the SW pin to minimize parasitic inductance. The exposed pad should be soldered to a large copper area for thermal management.
直接替換替代品，適用於 ST1S40PUR — 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： ST1S40PUR （相同外形與佔位） — 差異在於 Input Voltage Range, MSL Level, Maximum Output Current, Output Voltage Range, Package.
此產品無可直接替換的替代品。
申請替代品ST1S40PUR 最大額定值與電氣特性
| 輸出類型 | Adjustable |
| 輸出電壓範圍 | 0.8 V to VIN |
| 最大輸出電流 | 3 A |
| 輸入電壓範圍 | 4 V to 18 V |
| 切換頻率 | 1.5 MHz |
| 效率 | 90% (typical) |
| 靜態電流 | 1.5 mA |
| 關機電流 | 1 uA (max) |
| 熱阻 | 45 C/W |
| 工作溫度 | -40C to +150C |
| 封裝 | DFN6 (3x3 mm) |
| 安裝類型 | Surface Mount |
| MSL 等級 | 1 (unlimited) |
| RoHS 狀態 | Compliant |
| 致能腳位 | Yes (active-high) |
ST1S40PUR 腳位配置
| 腳位 1 | VIN — Input supply voltage |
| 腳位 2 | SW — Switch node output |
| 腳位 3 | GND — Ground |
| 腳位 4 | FB — Feedback voltage |
| 腳位 5 | EN — Enable (active high) |
| 腳位 6 | GND — Ground (exposed pad) |
典型應用
ST1S40PUR 適用於 6 應用s: Set-Top Box Power Supply, Networking Equipment, Industrial Control Systems, LCD TV Power Supply, FPGA and DSP Power, Distributed Power Systems.
Set-Top Box Power Supply
The ST1S40PUR efficiently converts a 12V input to 3.3V or 1.8V rails for core logic, reducing heat and improving reliability. Its 1.5MHz switching frequency allows small external components, fitting the compact form factor of set-top boxes. The high efficiency minimizes power loss, which is critical in enclosed consumer electronics. The device's overcurrent and thermal protection ensure safe operation under varying load conditions. With a wide input range, it can handle voltage fluctuations from the AC-DC adapter. The enable pin allows power sequencing with other rails, ensuring proper startup of the system.
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Networking Equipment
In networking equipment such as routers and switches, the ST1S40PUR provides a stable 3.3V or 1.8V rail for FPGAs and ASICs. Its high output current of 3A supports the power demands of high-performance processors. The 1.5MHz switching frequency reduces the size of the inductor and capacitors, saving PCB space in dense designs. The device's low quiescent current helps meet energy efficiency standards. The wide input range accommodates various system voltages, from 5V to 12V. The thermal pad in the DFN6 package aids heat dissipation, ensuring reliable operation in confined spaces.
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Industrial Control Systems
The ST1S40PUR is suitable for industrial control systems that require a robust power supply from a 24V bus. Its input voltage range of 4V to 18V allows it to operate from a 12V or 24V supply with proper derating. The device's high efficiency reduces heat generation, which is important in industrial enclosures with limited airflow. The overcurrent protection and thermal shutdown ensure safe operation in harsh environments. The adjustable output voltage allows it to generate various rails needed by microcontrollers and sensors. The compact DFN6 package is ideal for space-constrained control boards.
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LCD TV Power Supply
In LCD TVs, the ST1S40PUR converts the main 12V rail to lower voltages for the timing controller, T-con board, and other logic circuits. Its 3A output current can handle the peak currents of these circuits. The 1.5MHz switching frequency allows the use of small, low-profile inductors, which is beneficial for slim TV designs. The device's high efficiency reduces power consumption, contributing to energy star ratings. The enable pin allows the TV to power down the logic circuits in standby mode, reducing standby power. The thermal performance of the DFN6 package ensures reliable operation in the warm environment inside a TV.
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FPGA and DSP Power
The ST1S40PUR is ideal for powering FPGAs and DSPs that require a 1.8V or 3.3V rail with high current. Its 3A output current can supply the core voltage of many mid-range FPGAs. The adjustable output voltage allows precise setting of the core voltage. The high switching frequency reduces the size of the output filter, which is important in dense PCB layouts. The device's fast transient response ensures stable operation during dynamic load changes. The enable pin allows power sequencing with other rails, which is critical for FPGA startup.
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Distributed Power Systems
The ST1S40PUR is used in distributed power systems where a central 12V bus is converted to various lower voltages at the point of load. Its wide input range and high efficiency make it suitable for this role. The device's small footprint allows it to be placed close to the load, reducing I2R losses in the PCB traces. The 1.5MHz switching frequency enables the use of small inductors, which is beneficial in multi-rail systems. The overcurrent protection prevents damage to the load in case of a fault. The enable pin allows individual rails to be powered up or down as needed.
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推薦產品摘要
工程參考資料，適用於 ST1S40PUR — 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 | ST1S40PHR | TPS54331 | MP2307 |
|---|---|---|---|---|
| Package | DFN6 (3x3 mm) | PowerSO-8 | SOIC-8 | SOIC-8 |
| Brand | STMicroelectronics | STMicroelectronics | Texas Instruments | Monolithic Power Systems |
| Input Voltage Range | 4V to 18V | 4V to 18V | 3.5V to 28V | 4.75V to 23V |
| Output Current | 3A | 3A | 3A | 3A |
| Switching Frequency | 1.5MHz | 1.5MHz | 570kHz | 340kHz |
| Output Voltage Range | 0.8V to VIN | 0.8V to VIN | 0.8V to VIN | 0.8V to VIN |
| Quiescent Current | 1.5mA | 1.5mA | 150uA | 1mA |
| Enable Pin | Yes | Yes | Yes | Yes |
主要差異化特點
- Higher switching frequency (1.5MHz) enables smaller external components (對比TPS54331)
- Same die as ST1S40PHR but in a smaller DFN6 package (對比ST1S40PHR)
- Wide input voltage range (4V to 18V) with 3A output (對比MP2307)
設計說明
For optimal performance, place the input capacitor (10uF ceramic) as close as possible to the VIN pin and the output inductor (2.2uH to 4.7uH) close to the SW pin. Use a solid ground plane and short, wide traces for high-current paths. The exposed pad should be soldered to a large copper area for thermal dissipation.
The DFN6 package has a thermal resistance of 45°C/W. At 3A output with a 12V to 3.3V conversion, power dissipation is approximately 2.6W, resulting in a temperature rise of 117°C. Ensure adequate copper area and airflow to keep the junction temperature below 150°C.
Do not exceed the absolute maximum input voltage of 18V. Use a Schottky diode for the bootstrap capacitor if needed. Ensure the feedback resistor divider uses 1% tolerance resistors to maintain output voltage accuracy. The soft-start capacitor (if used) controls startup time; do not omit it if inrush current is a concern.
合規資訊
RoHS compliant per STMicroelectronics product page. Not AEC-Q100 qualified.
