原标题：ADI ADP1851 25A DC-DC降压电源解决方案

　　ADI 公司的ADP1851是宽输入电压同步降压控制器, 输入电压从2.75V到20V,输出电压从0.6 V 到90% VIN,输出电流大于25A,输出电压可跟踪,在整个温度范围内精度为±1%,可编程频率200 kHz 到1.5 MHz,可编软起动,主要用在通信基站和网络,工业和仪表,医疗和保健.本文介绍了ADP1851主要特性,方框图,典型应用电路,电压和电流模式输出25A应用电路图,以及评估板ADP1851-EVALZ主要特性,电路图,材料清单和PCB元件布局图.

　　The ADP1851 is a wide range input, dc-to-dc, synchronous buck controller capable of running from commonly used 3.3 V to 12 V (up to 20 V) voltage inputs. The device nominally operates in current mode with valley current sensing providing the fastest step response for digital loads. It can also be config-ured as a voltage mode controller with low noise and crosstalk for sensitive loads.

　　The ADP1851 is ideal in system applications requiring multiple output voltages. The ADP1851 includes a synchronization feature to eliminate beat frequencies between switching devices. It also provides accurate tracking capability between supplies and includes precision enable and power-good functions for simple, robust sequencing.

　　The ADP1851 provides a high speed, high peak current gate driving capability to enable energy efficient power conversion. The device can be configured to operate in power saving mode by skipping pulses, reducing switching losses, and improving efficiency at light load and standby conditions.

　　The accurate current limit allows design within a narrower range of tolerances and can reduce overall converter size and cost. The ADP1851 can regulate down to 0.6 V output using a high accuracy reference with ±1% tolerance over the temperature range of −0°C to +125°C.

　　With its wide range input voltage, the ADP1851 provides the designer with maximum flexibility for use in a variety of system configurations; loop compensation, soft start, frequency setting, power saving mode, current limit, and current sense gain can all be programmed using external components. In addition, the external RAMP resistor allows the selection of optimal slope and VIN feedforward in both current and voltage modes for excellent line rejection. The linear regulator and the bootstrap diode for the high-side driver are internal.

　　Protection features include undervoltage lockout, overvoltage, overcurrent/short circuit, and overtemperature.

　　ADP1851主要特性:

　　Input voltage range: 2.75 V to 20 V

　　Output voltage range: 0.6 V to 90% VIN

　　Maximum output current of more than 25 A

　　Current mode architecture

　　Configurable to voltage mode

　　±1% output voltage accuracy over temperature

　　Voltage tracking

　　Programmable frequency: 200 kHz to 1.5 MHz

　　Synchronization input

　　Power saving mode at light load

　　Precision enable input

　　Power good with internal pull-up resistor

　　Adjustable soft start

　　Programmable current sense gain

　　Integrated bootstrap diode

　　Starts into a precharged load

　　Externally adjustable slope compensation

　　Suitable for any output capacitor

　　Overvoltage and overcurrent-limit protection

　　Thermal overload protection

　　Input undervoltage lockout (UVLO)

　　Available in 16-lead, 4 mm × 4 mm LFCSP

　　Supported by ADIsimPower design tool

　　ADP1851应用:

　　Intermediate bus and POL systems requiring sequencing and tracking, including

　　Telecom base station and networking

　　Industrial and instrumentation

　　Medical and healthcare

　　图1.ADP1851简化框图

　　图2.ADP1851典型应用电路

　　图3.ADP1851电流模式的25A应用电路

　　图4.ADP1851电压模式的25A应用电路

　　评估板ADP1851-EVALZ

　　This document describes the design, operation, and test results of the ADP1851-EVALZ. The input voltage range for this evaluation board is 9 V to 15 V, and the regulated output voltage (VOUT) is set to 1.8 V with the maximum output current up to 25 A. The switching frequency (fSW) of 600 kHz is set to achieve high efficiency. The switching frequency can be also synchro-nized to an external clock signal applied to the SYNC input.

　　评估板ADP1851-EVALZ主要特性:

　　Input voltage range: 9 V to 15 V

　　Output voltage: 1.8 V

　　Output current: up to 25 A

　　Switching frequency: 600 kHz

　　Operates in PWM or PSM

　　Designed for evaluation of the ADP1851 functionality

　　Flexible and easy to re-configure and modify

　　图5.评估板ADP1851-EVALZ外形图

　　评估板ADP1851-EVALZ材料清单(BOM):