IR 公司的IR3859是全集成效率95%DC-DC同步降压稳压器，MOSFET和PWM控制器同封在单个封装内，开关频率从250kHz到1.5MHz可编程，效率大于95%，输入电压从1.5V到21V，输出电压从0.7V到0.9xVin.可连续提供9A负载电流，主要用在服务器，存储设备，嵌入通信系统，POL电源，网络通信，计算机外设电源和通用DC/DC转换器.本文介绍了IR3859主要特性，方框图， 典型应用框图， 输入12V，输出1.8V/9A POL转换器应用电路及其材料清单，以及IR3859 评估板主要特性， 评估板电路图和材料清单.

 The IR3859 SupIRBuckTM is an easy-to-use， fully integrated and highly efficient DC/DC synchronous Buck regulator. The MOSFETs copackaged with the on-chip PWM controller make IR3859 a space-efficient solution， providing accurate power delivery for low output voltage applications.IR3859 is a versatile regulator which offers programmability of start up time， switching frequency and current limit while operating in wide input and output voltage range.

 The switching frequency is programmable from 250kHz to 1.5MHz for an optimum solution.It also features important protection functions， such as Pre-Bias startup， hiccup current limit and thermal shutdown to give required system level security in the event of fault conditions.

 IR3859主要特性:

Greater than 95% Maximum Efficiency

Wide Input Voltage Range 1.5V to 21V

Wide Output Voltage Range 0.7V to 0.9*Vin

Continuous 9A Load Capability

Integrated Bootstrap-diode

High Bandwidth E/A for excellent transient performance

Programmable Switching Frequency up to 1.5MHz

Programmable Over Current Protection

Over Voltage Protection

Dedicated input for output voltage monitoring

Programmable PGood output

Hiccup Current Limit

Precision Reference Voltage (0.7V， +/-1%)

Programmable Soft-Start

Enable Input with Voltage Monitoring Capability

Enhanced Pre-Bias Start-up

Seq input for Tracking applications

External Synchronization

-40oC to 125oC operating junction temperature

Thermal Protection

4mm x 5mm Power QFN Package

Halogen Free， Lead Free and RoHS compliant

 IR3859应用:

Server Applications

Storage Applications

Embedded Telecom Systems

Distributed Point of Load Power Architectures

Netcom Applications

Computing Peripheral Voltage Regulators

General DC-DC Converters

图1.IR3859简化方框图

图2.IR3859典型应用框图

图3.IR3859应用电路图:输入12V，输出1.8V/9A POL转换器

 IR3859 评估板主要特性:

Vin = +12V (13.2V Max)

Vcc=+5V (5.5V Max)

Vout = +1.8V @ 0- 9A

Fs=600kHz

L= 0.68uH

Cin= 4x10uF (ceramic 1206) + 330uF (electrolytic)

Cout= 6x22uF (ceramic 0805)

图4.IR3859 评估板外形图

图5.IR3859 评估板电路图