原标题：NEC采用ADI ADP1829低压DC开关电源参考设计

　　NEC公司的低压DC开关电源参考设计是采用ADI公司的 ADP1829多功能双路同步PWM降压控制器. ADP1829固定工作频率为300kHz和60kHz,输入电压从3.0V到24V,输出电压从0.6V到输入电压的85%.主要应用在通信和网络系统,医疗图像系统,基站电源,机顶盒(STB),打印机和DDR电源.本文介绍ADP1829主要特性,方框图, 典型应用电路和输出20A电流应用电路以及采用ADP1829的低压DC开关电源参考设计主要特性,电路图和材料清单(BOM).

　　NEC ADP1829 Low Voltage DC-DC Switching Power　Reference Design

　　The ADP1829 is a versatile, dual, interleaved, synchronous PWM buck controller that generates two independent output rails from an input of 3.0 V to 18 V, with power input voltage ranging from 1.0 V to 24 V. Each controller can be configured to provide output voltages from 0.6 V to 85% of the input voltage and is sized to handle large MOSFETs for point-of-load regulators. The two channels operate 180° out of phase, reducing stress on the input capacitor and allowing smaller, low cost components. The ADP1829 is ideal for a wide range of high power applications, such as DSP and processor core I/O power, and general-purpose power in telecommunications, medical imaging, PC, gaming, and industrial applications. The ADP1829 operates at a pin-selectable, fixed switching frequency of either 300 kHz or 600 kHz, minimizing external component size and cost. For noise-sensitive applications, it can also be synchronized to an external clock to achieve switching frequencies between 300 kHz and 1 MHz. The ADP1829 includes soft start protection to prevent inrush current from the input supply during startup, reverse current protection during soft start for precharged outputs, as well as a unique adjustable lossless current-limit scheme utilizing external MOSFET sensing. For applications requiring power supply sequencing, the ADP1829 also provides tracking inputs that allow the output voltages to track during startup, shutdown, and faults. This feature can also be used to implement DDR memory bus termination. The ADP1829 is specified over the −40℃ to +125℃ junction temperature range and is available in a 32-lead LFCSP package.

　　This Low Voltage DC-DC Switching Power Reference Design uses the Analog Devices ADP1829 dual switching controller in conjunction with NEC Electronics uPA2725UT1A and uPA2723UT1A N-Channel MOSFETs in the thermally enhanced HVSON-8 packages. The input voltage range for this circuit is 4.8V – 13.2V. The output voltages and currents are as follows:

　　• VOUT1 = 1.2 V with a maximum output current of 20.0 A

　　• VOUT2 = 3.3 V with a maximum output current of 20.0 A

　　The uPA2723UT1A acts as the synchronous or “low side” switch, while the PA2725UT1A operates as the primary or “high side” switch. The ADP1829 synchronous buck has active break-before-make circuitry as well as a supplemental fixed　dead time, which are used to prevent both switches from being on simultaneously preventing possible catastrophic failures.

　　In low conversion ratio and higher current synchronous buck configurations, it is vital to select a low on-resistance MOSFET in the low side switch. This has been accomplished with the uPA2723UT1A, which has a typical on-resistance of 2.6 m Ohm with a gate-to-source drive voltage of 4.5 V. With this very low on-resistance, conduction losses can be minimized and a high efficiency can be achieved.

　　Additionally it is necessary to use a low gate-charge MOSFET in the high side switch to reduce switching losses. For this design, the uPA2725UT1A has been selected for its low gate-charge rated at approximately 18 nC for an input voltage of 12 V and drive voltage of 4.5 V. These impressive MOSFET parameters are coupled with the low on-resistance driver technology in the ADP1829 dual controller.

　　ADP1829主要特性:

　　Fixed frequency operation: 300 kHz, 600 kHz, or synchronized operation up to 1 MHz

　　Supply input range: 3.0 V to 20 V

　　Wide power stage input range: 1 V to 24 V

　　Interleaved operation results in smaller, low cost input capacitor

　　All-N-channel MOSFET design for low cost ±0.85% accuracy at 0C to 70C

　　Soft start, thermal overload, current-limit protection 10 μA shutdown supply current

　　Internal linear regulator

　　Lossless RDSON current-limit sensing

　　Reverse current protection during soft start for handling precharged outputs

　　Independent Power OK outputs

　　Voltage tracking for sequencing or DDR termination

　　Available in 5 mm×5 mm, 32-lead LFCSP

　　ADP1829应用:

　　Telecommunications and networking systems

　　Medical imaging systems

　　Base station power

　　Set-top boxes

　　Printers

　　DDR termination

　　图1.ADP1829方框图

　　图2.ADP1829典型应用电路

　　图3.ADP1829输出20A应用电路

　　图4.全部采用多层陶瓷电容(MLCC)的ADP1829应用电路

　　低压DC开关电源参考设计

　　This Low Voltage DC-DC Switching Power Reference Design offers an efficient and cost-effective solution for low voltage　DC-DC power conversion.

　　低压DC开关电源参考设计主要特性:

　　A high efficiency and cost-effective solution for low voltage DC-DC power conversion

　　Wide Input Voltage Range: 4.8V – 13.2V

　　Two Regulated Output Voltages: 1.2 V & 3.3 V

　　Output Current: 20.0 A on both 1.2V and 3.3V Rails

　　图5.低压DC开关电源参考设计PCB外形图

　　图6.低压DC开关电源参考设计电路图

　　低压DC开关电源参考设计材料清单(BOM):