NS LM20145 5A降压稳压器方案

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[组图]NS LM20145 5A降压稳压器方案

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NS LM20145 5A降压稳压器方案

作者：NS 文章来源：NS 点击数：更新时间：2008-2-27

NS 的LM20145 连续输出电流高达 5A, 是PowerWise®可调频率同步降压稳压器，采用恒流模式控制回路，对各种输出电容能稳定工作，器件的输入电压2.95V 到 5.5V，内部具有过压保护(OVP)和过流保护(OCP)，广泛应用于各种低电压系统如5V 或 3.3V总线，高性能DSP, FPGA, ASIC和微处理器以及宽带，网络与光纤通信等设备。本文描述 LM20145的主要特性，方框图和应用电路图，所用元器件清单，LM20145演示板的主要特性。

The LM20145 demonstration board has been designed to balance overall solution size with the efficiency of the regulator. The demonstration board measures just 1.0 x 1.0 on a two layer PCB, with all components placed on the top layer. The power stage and compensation components of the LM20145 demonstration board have been optimized for an input voltage of 5V, but for testing purposes, the input can be varied across the entire operating range. The output voltage of the evaluation board is nominally 2.5V. The control loop compensation of the LM20145 demonstration board has been designed to provide a stable solution over the entire input and output voltage range with a reasonable transient response. The EN pin is connected to VIN through a 100kOhm resistor which will enable the device when power is applied.
主要特性：
Optimized for 5V to 2.5V conversion
5A output current, 89% efficiency
1.5%output voltage accuracy
500 kHz switching frequency
Peak current mode control
Starts up into pre-biased loads
Soft-Start set by external capacitor
Precision enable pin with hysteresis
Integrated OVP, UVLO, power good and thermal shutdown
Accurate current limit with frequency foldback
Input voltage range 2.95V to 5.5V

应用：
Simple to design, high efficiency point of load regulation from a 5V or 3.3V bus
High Performance DSPs, FPGAs, ASICs and microprocessors
Broadband, Networking and Optical Communications Infrastructure

图1。板外形图

LM20145 5A, PowerWise®可调频率同步降压稳压器性能：
LM20145 5A, PowerWise® Adjustable Frequency Synchronous Buck Regulator
LM20145概述：

The LM20145 is a full featured adjustable frequency synchronous buck regulator capable of delivering up to 5A of continuous output current. The current mode control loop can be compensated to be stable with virtually any type of output capacitor. For most cases, compensating the device only requires two external components, providing maximum flexibility and ease of use. The device is optimized to work over the input voltage range of 2.95V to 5.5V making it suited for a wide variety of low voltage systems.
The device features internal over voltage protection (OVP) and over current protection (OCP) circuits for increased system reliability. A precision enable pin and integrated UVLO allows the turn-on of the device to be tightly controlled and sequenced. Start-up inrush currents are limited by both an internally fixed and externally adjustable Soft-Start circuit.

Fault detection and supply sequencing is possible with the integrated power good circuit.

The LM20145 is designed to work well in multi-rail power supply architectures. The output voltage of the device can be configured to track a higher voltage rail using the SS/TRK pin.
If the output of the LM20145 is pre-biased at startup it will not sink current to pull the output low until the internal soft-start ramp exceeds the voltage at the feedback pin.
The frequency of this device can be adjusted from 250 kHz to 750 kHz by connecting an external resistor from the RT pin to ground.
The LM20145 is offered in a 16-pin eTSSOP package with an exposed pad that can be soldered to the PCB, eliminating the need for bulky heatsinks.

主要特性：
■ Input voltage range 2.95V to 5.5V
■ Accurate current limit minimizes inductor size
■ 97% peak efficiency
■ Adjustable switching frequency (250 kHz to 750 kHz)
■ 32 mΩ integrated FET switches
■ Starts up into pre-biased loads
■ Output voltage tracking
■ Peak current mode control
■ Adjustable output voltage down to 0.8V
■ Adjustable Soft-Start with external capacitor
■ Precision enable pin with hysteresis
■ Integrated OVP, UVLO, power good and thermal shutdown
■ eTSSOP-16 exposed pad package

器件应用：
■ Simple to design, high efficiency point of load regulation from a 5V or 3.3V bus
■ High Performance DSPs, FPGAs, ASICs and microprocessors
■ Broadband, Networking and Optical Communications Infrastructure

图2。LM20145方框图

图3。LM20145应用电路图

下表为LM20145应用电路图中所用元器件清单：

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