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RT7272BGSP Evaluation Board

EVB_RT7272BGSP

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The RT7272B 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 RT7272B 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 RT7272B 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 RT7272B 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 RT7272B provides complete protection functions such as input under voltage lockout, output under voltage protection, over current protection and thermal shutdown.

The RT7272B 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

RT7272BGSP, SOP-8 (Exposed Pad)

Operation Frequency

Steady 500kHz at PWM

Other Key Features

4.5V to 36V Wide Input Voltage Range

Adjustable Current Limit 2A to 6A

PSM/ PWM Auto Switched.

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 RT7272B 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

RT7272BGSP

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

NR8040T4R7N

4.7μH/4.1A/±30%,
DCR=18mΩ, Inductor

8.00mm x 8.00mm

TAIYO YUDEN

WE74437368047

4.7μH/19A/±20%,
DCR=15mΩ, Inductor

11mm x 10mm x 3.8mm

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)

Technical Document Image Preview

Bottom View (4thLayer)

Technical Document Image Preview

Component Placement Guide—Component Side (1stlayer)

Technical Document Image Preview

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)

Technical Document Image Preview

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 2019/09/16
Bill of Materials 2019/09/16
Gerber File 2015/09/24
Schematic 2015/09/30
RT7272B

3A, 36V, 500kHz Synchronous Step-Down Converter

RT7272B

The RT7272B 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 a 80mΩ low side MOSFET to achieve high conversion efficiency up to 95%. The current mode control architecture supports fast transient response and simple compensation circuit.

A cycle-by-cycle current limit function provides protection against shorted output and an internal soft-start eliminates input current surge during start-up. The RT7272B provides complete protection functions such as input under-voltage lockout, output under-voltage protection, over-current protection and thermal shutdown.

The RT7272B is available in the thermal enhanced SOP-8 (Exposed Pad) package.

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