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RT8279 Step-Down Converter Evaluation Board

EVB_RT8279GSP

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The RT8279 is a step-down regulator with an internal power MOSFET. It achieves 5A of continuous output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. For protection, the RT8279 provides cycle-by-cycle current limiting and thermal shutdown protection. An adjustable soft-start reduces the stress on the input source at start up. In shutdown mode, the regulator draws only 25μA of supply current. The RT8279 requires a minimum number of readily available external components, providing a compact solution. The RT8279 is available in the SOP-8 (Exposed Pad) package.

Purpose

The RT8279 is a Current mode operation step-down regulator with an internal power MOSFET. This document explains the function and use of the RT8279 evaluation board (EVB) and provides information to enable operation and modification of the evaluation board and circuit to suit individual requirements.

Introduction

General Product Description

The RT8279 is a step-down regulator with an internal power MOSFET. It achieves 5A of continuous output current over a wide input supply range with excellent load and line regulation. Current mode operation provides fast transient response and eases loop stabilization. For protection, the RT8279 provides cycle-by-cycle current limiting and thermal shutdown protection. An adjustable soft-start reduces the stress on the input source at start up. In shutdown mode, the regulator draws only 25μA of supply current. The RT8279 requires a minimum number of readily available external components, providing a compact solution. The RT8279 is available in the SOP-8 (Exposed Pad) package.

Product Features

  • 5A Output Current
  • Internal Soft-Start
  • 110mΩ Internal Power MOSFET Switch
  • Internal Compensation Minimizes External Parts Count
  • High Efficiency up to 90%
  • 25μA Shutdown Mode
  • Fixed 500kHz Frequency
  • Thermal Shutdown
  • Cycle-by-Cycle Over Current Protection
  • Wide 5.5V to 36V Operating Input Range
  • Adjustable Output Voltage from 1.222V to 26V
  • Available In an SOP-8 (Exposed Pad) Package
  • RoHS Compliant and Halogen Free

Application

  • Distributive Power Systems
  • Battery Charger
  • DSL Modems
  • Pre-regulator for Linear Regulators

Evaluation Board

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Please carefully inspect the EVB IC and external components, comparing them to the following Bill of Materials, to ensure that all components are installed and undamaged. If any components are missing or damaged during transportation, please contact the distributor or send e-mail to evb_service@richtek.com

Test Points

The EVB is provided with the test points and pin names listed in the table below.

Test point/Pin name

Signal

Comment (expected waveforms or voltage levels on test points)

VIN

Input voltage

Input voltage range = 5.5V to 36V

VOUT

Output voltage

Output voltage = 2.4V

SW

Switch Node

EN

Chip Enable Operation

The EN pin is externally pulled to High by adding a 100kΩ resistor (R4) from the VIN pin in this EVB setting. For another enable operation, pull the EN pin low (<0.4V) will shutdown the device, drive the EN pin to high (>1.4V, <5.5V) will turn on the device again.

GND

Ground

Ground

Power-up & Measurement Procedure

1. Connect input power (5.5V< VIN < 36V) and input ground to Vin and GND pins respectively.

2. Connect positive end and negative end of load to VOUT and GND of output pins respectively.

3. The output voltage of (VOUT) can be set by R1 and R2.

VOUT = VREF * (1+R1/R2)

where VREF = 1.222V (typ.)

Specification

Parameter

Symbol

Min

Typ.

Max

Units

Input Voltage Range

VIN

5.5

36

V

Output Voltage

VOUT

2.4

V

Oscillator Frequency

fOSC

425

500

575

kHz

Output Current

IOUT

5

A

Current Limit

ILIM

6

7.5

9

A

Schematic

Technical Document Image Preview

BOM

Reference

Q'ty

P/N

Description

Package

Manufacture

U1

1

RT8279GSP

Step-down converter

SOP-8

RICHTEK

C1, C2

2

GRM32ER71H475K

4.7μF/50V/X7R

C-1210

MURATA

C3, C6, C11

3

C1608X7R1H104K080AA

0.1μF/±10%/50V/X7R

C-0603

TDK

C4, C5

2

GRM32ER61C226KE20

22μF/±10%/16V/X5R

C-1210

MURATA

C12

1

82pF

C-0603

L1

1

74437368068

6.8μH, 6A, ±20%, DCR = 23.3mΩ

10 x 10 x 3.8mm

WE-LHMI

D1

1

B550C

50V/5A

DIODES

R1, R2, R4

3

100k

R-0402

C8, R5

2

NC

PCB Layout

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PCS Layout (1st layer)

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PCS Layout (2nd layer)

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PCS Layout (3rd layer)

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PCS Layout (4th layer)

Step-Down Converter Efficiency Test

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Title Last Update Share Download
Evaluation Board User Guide 2015/06/29
Bill of Materials 2015/06/29
Gerber File 2015/09/18
Schematic 2015/09/18
RT8279

5A, 36V, 500kHz 降压型 DC/DC 转换器

RT8279

RT8279为内置功率开关元件的降压型转压器,可在宽输入电压范围内达到5A的的连续电流输出,并具有良好的负载与电源电压调节率,电流模式操作提供快速的瞬时响应与简易的回路稳定架构。RT8279并提供了逐周期形式的限流机制与热关断保护功能,操作在关机模式时,转换器只有25µA的低电流消耗。RT8279只需要少数的外部元件,提供更便利轻巧的应用方案。RT8279采用SOP-8 (裸露焊盘)的封装规格。

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