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
Operats 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

图6.评估板ADP1851-EVALZ电路图

评估板ADP1851-EVALZ材料清单(BOM):



图7.评估板ADP1851-EVALZ PCB元件布局图(顶层)

图8.评估板ADP1851-EVALZ PCB元件布局图(底层)