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RT7279GQW Evaluation Board

EVB_RT7279GQW

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The RT7279 is a high-performance 700kHz 2A step down regulator with an internal power switch and synchronous rectifier. It features quick transient response using its Advanced Constant On-Time (ACOTTM) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 8V.

Purpose

The RT7279 is a high-performance 700kHz 2A step down regulator with an internal power switch and synchronous rectifier. This document explains the function and use of the RT7279 evaluation board (EVB) and provides information to enable operation and modification of the evaluation board and circuit to suit individual requirements.

Introduction

General Product Information

The RT7279 is a high-performance 700kHz 2A step down regulator with an internal power switch and synchronous rectifier. It features quick transient response using its Advanced Constant On-Time (ACOTTM) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 8V.

The proprietary ACOTTM control improves upon other fast response constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. The RT7279 is stable with and optimized for ceramic output capacitors.

With its internal 90mΩ switch and 60mΩ synchronous rectifier, the RT7279 displays excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-by cycle current limit, input under-voltage lock-out, externally-adjustable soft-start, output under- and overvoltage protection, and thermal shutdown provide safe and smooth operation in all operating conditions.

The RT7279 evaluation board uses the RT7279GQW IC in a WDFN-10L3x3 package with an exposed thermal pad. The IC is also available in a PTSSOP-14 package with an exposed thermal pad.

Product Feature

  • Fast Transient Response
  • Steady 700kHz Switching Frequency at All Load
  • 2A Output Current
  • Advanced Constant On-Time (ACOTTM) Control
  • Optimized for Ceramic Output Capacitors
  • 4.5V to 18V Input Voltage Range
  • Internal 90mΩ Switch and 60mΩ Synchronous Rectifier
  • 0.765V to 8V Adjustable Output Voltage
  • Externally-adjustable, Pre-biased Compatible Soft-Start
  • Cycle-by-Cycle Current Limit
  • Output Over- and Under-voltage Shut-down

Key Performance Summary Table

Key features

Evaluation board number: PCB002_V1

Default Input voltage

12V

Max Output Current

2A

Default Output Voltage

1.05V

Default Marking & Package Type

RT7279GQW (WDFN-10L 3x3)

Operation Frequency

Steady 700kHz at all load

Other Key Features

Advanced constant On-time(ACOTTM) control

Power Good

Adjustable Soft-start (external capacitor)

Protection

Over current protection:

Cycle-by-Cycle Current Limit

Hiccup Mode Output Over- and Under-voltage Shut-down

 

Bench Test Setup Conditions

Headers Description and Placement

Technical Document Image Preview

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 = 4.5V to 18V

VOUT

Output voltage

Default output voltage = 1.05V

Output voltage range = 0.765V to 8V

(see ‘’ Output Voltage Setting’’ section for changing output voltage level)

GND

Ground

Ground reference for the input voltage, output voltage and analog ground

SW

Switching node test point

SW waveform

EN

Enable test point

Enable signal. Drive EN or install a shorting block on Jumper JP1 to enable operation (shorting 2-3) or disable operation (shorting 1-2).

JP1

Chip enable control

Install jumper or drive EN directly to enable or disable operation

BOOT

Boot strap supply test point

Floating supply voltage for the high-side N-MOSFET switch

SS

Soft-start control test point

Soft start waveform

PVCC

Linear regulator output test point

Internal linear regulator output= 5.1V

PG

Power good output test point

Connected to PVCC through R29, PG voltage is 5.1V when soft-start is complete and the output voltage is in regulation

 

Power-up & Measurement Procedure

1.Connect a jumper at JP1 terminals 1 and 2, connecting EN to GND, to disable operation.

2.Apply a 12V nominal input power supply (4.5V < VIN < 18V) to the VIN and GND terminals.

3.Set the jumper at JP1 to connect terminals 2 and 3, connecting EN to VIN through resistor R30, to enable operation.

4.Verify the output voltage (approximately 1.05V) between VOUT and GND.

5.Connect an external load up to 2A to the VOUT and GND terminals and verify the output voltage and current.

Output Voltage Setting

Set the output voltage with the resistive divider (R23, R28) between VOUT and GND with the midpoint at FB. The output is set by the following formula:

Technical Document Image Preview

 

The installed VOUT capacitors (C11, C12) are 22μF, 16V X5R ceramic types. Do not exceed their operating voltage range and consider their voltage coefficient (capacitance vs. bias voltage) and ensure that the capacitance is sufficient to maintain stability and provide sufficient transient response for your application. Installing a small 5pF to 22pF capacitor at C30 (in parallel with R23) may be desirable to improve transient response for higher output voltages. See the RT7279 IC datasheet for more information.

Schematic, Bill of Materials and Board Layout

EVB Schematic Diagram

Technical Document Image Preview

C7, C9: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K

C11, C12: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K

L1: 2.0μH TAIYO YUDEN NR8040T2R0N, DCR=9mΩ

Bill of Materials

Reference

Qty

Part number

Description

Package

Manufacture

U5

1

RT7279GQW

DC/DC Converter

WDFN-10L 3x3

Richtek

C7,C9

2

C3216X5R1H106K160AB

10μF/±10%/50V/X5R

Ceramic Capacitor

1206

TDK

C11,C12

2

GRM32ER61C226KE20#

22μF/±10%/16V/X5R

Ceramic Capacitor

1210

Murata

C28

1

0603B392K500

3.9nF/±10%/50V/X7R

Ceramic Capacitor

0603

WALSIN

C8,C10,C27

3

C1608X7R1H104K080AA

0.1μF/±10%/50V/X7R

Ceramic Capacitor

0603

TDK

C29

1

C1608X5R1E105K080AC

1μF/±10%/25V/X5R

Ceramic Capacitor

0603

TDK

C30

0

Not Installed

0603

L1

1

NR8040T2R0N

2.0μH/6.3A/±30%,

DCR=9mΩ, Inductor

8mmx8mmx4mm

TAIYO YUDEN

L2

0

Not Installed

R28

1

22k/±5%, Resistor

0603

R23

1

8.2k/±5%, Resistor

0603

R29

1

10k/±5%, Resistor

0603

R30

1

100k/±5%, Resistor

0603

CP1

1

0 (Short)

JP1

1

3-Pin Header

TP1/2/3/4/5/6

6

Test Pin

GP

5

Golden Pin

 

EVB Layout

Technical Document Image Preview

Top View (1stlayer)

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Bottom View (4thLayer)

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Component Placement Guide—Component Side (1stlayer)

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PCB Layout—Component Side (1stLayer)

Technical Document Image Preview

PCB Layout—Inner Side (2nd Layer)

Technical Document Image Preview

PCB Layout—Inner Side (3rd Layer)

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Component Placement Guide—Bottom Side (4th Layer)

Technical Document Image Preview

PCB Layout—Bottom Side (4th layer)

Title Last Update Share Download
Evaluation Board User Guide 2015/06/05
Bill of Materials 2015/06/05
Gerber File 2015/09/24
Schematic 2015/09/30
RT7274/RT7279/RT7280/RT7281

2A, 18V, 700kHz ACOT™ 同步降压型 DC/DC 转换器

RT7274/RT7279/RT7280/RT7281

RT7274/79/80/81 系列为ACOT(Advanced Constant On-Time)操作模式之同步整流降压式直流转换器,输入电压4.5V至18V范围内,最大电流输出为2A。系统操作于ACOT模式下可在广负载变动范围内提供良好的瞬时响应,并于输出电容的选择上可选用具较小ESR的陶瓷电容,并确保整体系统表现的稳定性。此外,RT7274/79/80/81 在输入与负载变动情形下仍能提供良好的恒定操作频率表现,内建的整流开关可允许在输出在全负载变动范围内提供良好的转换效率。藉由侦测同步整流开关的端电压可达到逐周期形式的限流机制,并可藉由外部的电容设计达到缓启动效果,消除启动时产生过大的输入电涌。在保护机制方面,RT7274/79/80/81 均有过热保护功能,而RT7279/80 则另含有输出过电压保护功能。

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