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RT2872 Step-Down Converter Evaluation Board

EVB_RT2872GSP

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The RT2872 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 105mΩ 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 RT2872 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 RT2872 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 RT2872 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 105mΩ 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 RT2872 provides complete protection functions such as input under voltage lockout, output under voltage protection, over current protection and thermal shutdown.

The RT2872 is available in the thermal enhanced SOP-8 (Exposed Pad) package.

Product Features

  • 4.5V to 36V Input Voltage Range
  • 3A Output Current
  • Internal N-MOSFETs
  • Current Mode Control
  • Frequency Operation : 300kHz to 1MHz
  • 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
  • AEC-Q100 Grade 3 Certification

Application

  • Point of Load Regulator in Distributed Power Systems
  • Digital Set Top Boxes
  • Broadband Communications
  • Vehicle Electronics
  • Automotive Audio, Navigation, and Information Systems
  • Enterprise Datacom Platforms Point of Load (POL)
  • Industrial Grade General Purpose Point of Load

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 = 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

Switch Node

SW waveform

EN

Chip Enable Operation

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

RT test point

Switch frequency 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:

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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 RT2872 IC datasheet.

Specification

Parameter

Symbol

Min

Typ.

Max

Units

Input Voltage Range

VIN

4.5

36

V

Output Voltage

VOUT

3.3

V

Oscillator Frequency

fOSC

300k

1M

Hz

Output Current

IOUT

3

A

High-Side Switch Current Limit Range

UOC

4.25

5

5.75

A

Schematic

Technical Document Image Preview

BOM

Reference

Q'ty

P/N

Description

Package

Manufacture

U1

1

RT2872GSP

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

8 x 8 x 4.2mm

TAIYO YUDEN

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

RT

1

113kΩ/±1%, Resistor

0603

TP

4

Test Pin

GP

4

Golden Pin

PCB Layout

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Top View (1st layer)

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Bottom View (4th Layer)

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Component Placement Guide—Component Side (1st layer)

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PCB Layout—Component Side (1st Layer)

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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)

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PCB Layout—Bottom Side (4th layer)

Step-Down Converter Efficiency Test

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Title Last Update Share Download
Evaluation Board User Guide 2015/09/24
Bill of Materials 2015/07/01
Gerber File 2015/09/24
Schematic 2015/09/30
RT2872

3A, 36V同步降壓型轉換器

RT2872

RT2872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105mΩ 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RT2872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。RT2872提供SOP-8(裸露焊盤)封裝。

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