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RT7272AGSP Evaluation Board

EVB_RT7272AGSP

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The RT7272A is a high efficiency, current mode synchronous step-down DC/DC converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. The device integrates a 150mΩ high side and an 80mΩ low side MOSFET to achieve high conversion efficiency up to 95%. The current mode control architecture supports fast transient response and uses a simple compensation circuit.

Purpose

The RT7272A is a high-efficiency current mode synchronous step-down regulator that can deliver up to 3A output current from a wide input voltage range of 4.5V to 36V. This document explains the function and use of the RT7272A 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 RT7272A is a high efficiency, current mode synchronous step-down DC/DC converter that can deliver up to 3A output current over a wide input voltage range from 4.5V to 36V. The device integrates a 150mΩ high side and an 80mΩ low side MOSFET to achieve high conversion efficiency up to 95%. The current mode control architecture supports fast transient response and uses a simple compensation circuit.

A cycle-by-cycle current limit function provides protection against a shorted output and an internal soft-start eliminates input surge current during start-up. The RT7272A provides complete protection functions such as input under voltage lockout, output under voltage protection, over current protection and thermal shutdown.

The RT7272A is available in the thermal enhanced SOP-8 (Exposed Pad) package.

Product Feature

  • 4.5V to 36V Input Voltage Range
  • 3A Output Current
  • Internal N-MOSFETs
  • Current Mode Control
  • Fixed Frequency Operation : 500kHz
  • Adjustable Output Voltage from 0.8V to 30V
  • High Efficiency Up to 95%
  • Stable with Low ESR Ceramic Output Capacitors
  • Cycle-by-Cycle Current Limit
  • Adjustable Current Limit

Key Performance Summary Table

Key features

Evaluation board number: PCB001_V1

Default Input Voltage

12V

Max Output Current

3A (OCP level set to 5.5A typical by RLIM = 137kΩ)

Default Output Voltage

3.3V

Default Marking & Package Type

RT7272AGSP, SOP-8 (Exposed Pad)

Operation Frequency

Steady 500kHz at all load currents

Other Key Features

4.5V to 36V Wide Input Voltage Range

Adjustable Current Limit 2A to 6A

Protection

Over Current Protection &

Output Under-Voltage-Protection (hiccup mode)

Input Under-voltage Lock-out

Thermal Shutdown

 

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 36V

VOUT

Output voltage

Default output voltage = 3.3V

Output voltage range= 0.8V to 30V

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

SW

Switching node test point

SW waveform

EN

Enable test point

Enable signal. EN is automatically pulled high (by R4) to enable operation. Connect EN low to disable operation.

BOOT

Boot strap supply test point

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

MODE

RLIM test point

Current limit setting point

GND

Ground

Ground

 

Power-up & Measurement Procedure

1.Apply a 12V nominal input power supply (4.5V < VIN < 36V) to the VIN and GND terminals.

2.The EN voltage is pulled to logic high by R4 (100kΩ to VIN) to enable operation. Drive EN high (>2.0V) to enable operation or low (<0.4V) to disable operation.

3.Verify the output voltage (approximately 3.3V) between VOUT and GND.

4.Connect an external load up to 3A to the VOUT and GND terminals and verify the output voltage and current.

Output Voltage Setting

Set the output voltage with the resistive divider (R1, R2) between VOUT and GND with the midpoint connected to FB through RCAMP. The output is set by the following formula:

Technical Document Image Preview

The installed VOUT capacitors (C4, C5) 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. This can be verified by checking the output transient response as described in the RT7272A IC datasheet.

Schematic, Bill of Materials and Board Layout

EVB Schematic Diagram

Technical Document Image Preview

C1, C2: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K

C4, C5: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K

L1: 4.7μH WE74437368047, DCR=15mΩ

Bill of Materials

Reference

Qty

Part number

Description

Package

Manufacture

U1

1

RT7272AGSP

DC/DC Converter

PSOP-8

Richtek

C1, C2

2

C3216X5R1H106K160AB

10μF/±10%/50V/X5R

Ceramic Capacitor

1206

TDK

C4, C5

2

GRM32ER61C226KE20#

22μF/±10%/16V/X5R

Ceramic Capacitor

1210

Murata

C7

1

0603B272K500

2.7nF/±10%/50V/X7R

Ceramic Capacitor

0603

WALSIN

C3, C6, C11

3

C1608X7R1H104K080AA

0.1μF/±10%/50V/X7R

Ceramic Capacitor

0603

TDK

C8,C9,C12,C13

0

Not Installed

0603

L1

1

WE74437368047

4.7μH/19A/±20%,
DCR=15mΩ, Inductor

11mmx10mmx3.8mm

WE

R1

1

75kΩ/±1%, Resistor

0603

R2

1

24kΩ/±1%, Resistor

0603

R3

1

13kΩ/±1%, Resistor

0603

R4

1

100kΩ/±1%, Resistor

0603

R5, D1, D2

0

Not Installed

R6, RCAMP

2

0Ω, Resistor

0603

RLIM

1

137kΩ/±1%, Resistor

0603

TP

4

Test Pin

GP

4

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)

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PCB Layout—Inner Side (2nd Layer)

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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 (4thlayer)

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
RT7272A

3A, 36V, 500kHz 同步降壓型 DC/DC 轉換器

RT7272A

RT7272A為高效率,電流模式操作的同步降壓型 DC/DC 轉換器,在輸入電壓範圍4.5V至36V間,可輸出電流達3A。整合了高端150mΩ 與80mΩ 低端的MOSFET以達到95%的高轉換效率。電流模式的控制架構可支援快速的暫態回應與簡易的補償方式。逐週期形式的限流機制可在輸出短路時提供電路保護作用,內建的緩啟動機制則可消除啟動瞬間的輸入電流湧浪的問題。此外RT7272A提供了完整的保護功能,例如輸入低電壓鎖定機制,輸出低電壓保護、過電流保護與與熱關斷保護功能。RT7272A採用SOP-8(裸露焊盤)的封裝規格。

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