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Synchronous Step-Down Converter’s Evaluation Board for RT7238 Integrated Chip

EVB_RT7238BGQUF

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The RT7238B/C/D is an advanced constant on-time (ACOT™) mode synchronous step-down converter. The main control loop of RT7238B/C/D using an advanced constant on-time (ACOT™) mode control which provides a very fast transient response. The RT7238B/C/D operates from 8V to 23V input voltage. For the RT7238D, the output voltage can be adjusted between 0.6V to 5V. The RT7238B/C/D is available in the UQFN-10L 3x3 (FC) package.

Purpose

The RT7238B/C/D is an advance integrative chip, which includes a LDO regulator and a synchronous Buck converter. This document explains the function and use of the RT7238 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 RT7238B/C/D is an advanced constant on-time (ACOT™) mode synchronous step-down converter. The main control loop of RT7238B/C/D using an advanced constant on-time (ACOT™) mode control which provides a very fast transient response. The RT7238B/C/D operates from 8V to 23V input voltage. For the RT7238D, the output voltage can be adjusted between 0.6V to 5V. The RT7238B/C/D is available in the UQFN-10L 3x3 (FC) package.


Product Features

  • Advanced Constant On-Time (ACOT) Control
  • 8V to 23V (RT7238B/C/D) Input Voltage Range @ 8A Output Current
  • ACOT™ Mode Performs Fast Transient Response
  • ACOT™ Architecture to Enable all MLCC Output Capacitor Usage
  • Fixed 500kHz Switching Frequency
  • High Efficient Internal Power MOSFET Switch
  • ► 27mΩ (High-Side) and 10mΩ (Low-Side)
  • Adjustable Output Voltage from 0.9V to 5V (RT7238D)
  • Fixed 3.3V (RT7238B/D) or 5V (RT7238C) LDO Output Supplies 70mA
  • Pre-biased Soft-Start Cycle-by-Cycle Over-Current Protection
  • Input Under-Voltage Lockout
  • Thermal Shutdown
  • Output Over/Under-Voltage Protection

 

Application

  • Industrial and Commercial Low Power Systems
  • Computer Peripherals
  • LCD Monitors and TVs
  • Green Electronics/Appliances
  • Point of Load Regulation for High-Performance DSPs, FPGAs, and ASICs

 

Key Performance Summary Table

Key Features

Evaluation Board Number : PCB029_V1

Default Input Voltage

8V to 23V

Max Output Current

8A

Default Output Voltage

3.3V (RT7238B)

5.1V (RT7238C)

1.05V (RT7238D)

Default Marking & Package Type

RT7238B/C/D, UQFN-10L 3x3 (FC)

Operation Frequency

500kHz



Evaluation Board

Technical Document Image Preview

Technical Document Image Preview

RT7238B Top View

RT7238B Bottom View

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, Jumpers and Switches

The EVB is provided with the test points, jumpers, switches and individual names listed in the table below.

Test point/ name

Signal

Description (expected waveforms or voltage levels on test points)

VIN

Input voltage

Input voltage range

8V to 23V

VOUT

Output voltage

Output voltage

3.35V(RT7238B), 5.1V(RT7238C), adjustable(RT7238D)

LX

LX voltage

Switch Node

BS

BOOT voltage

Bootstrap supply for high-side gate driver.

EN2/LDO/BYP

EN2/LDO/BYP voltage

Enable Control Input of the IC and Internal LDO for RT7238B

Internal 5V LDO Output for RT7238C

Bypass Input for the Internal LDO for RT7238D

LDO/VCC/LDO

LDO/VCC/LDO voltage

Internal 3.3V LDO Output for RT7238B/D

No Internal Connection for RT7238C

FB/FB/ILMIT

LDO/VCC/LDO voltage

Current Limit Setting for RT7238D

No Internal Connection for RT7238B/C

PG

PG voltage

Power Good Indicator.This pin connect to LDO output through R3.

EN1/EN/EN

EN1/EN/EN voltage

Enable Control Input of the DC/DC Regulator.

GND

Ground

Ground


Jumpers/ name

Signal

Description (expected waveforms or voltage levels on test points)

JP1

Output voltage

Output voltage

3.35V(RT7238B), 5.1V(RT7238C), adjustable(RT7238D)

JP2

Current Limit Setting voltage

This jumper only provides current limit setting function for RT7238D Please remove R16, short R10 R14 C18 and short this jumper when setting the current limit.

JP3

VOUT/BYP/EN2 voltage

This jumper provides different setteings for RT7238B/D.

When this EVB applis for RT7238D, this jumper can provide BYP pin bypass to buck output voltage function as BYP shorting to VOUT.When this EVB applis for RT7238B, please short the BYP to EN2.


Switches/ name

Signal

Description (expected waveforms or voltage levels on test points)

SW1

EN1 voltage

EN2 voltage

ILMT_L voltage

ILMT_H voltage

This switch provide EN1, EN2, and current limit setting functions.

When this EVB applis for RT7238C/D/E, the EN1 switch is used to enable EN.

When this EVB applis for RT7238D, it can set ILMIT pin to “floating” by turn off ILMT_L and ILMT_H, “0” by turn on ILMT_L and turn off ILMT_H and “1” by turn off ILMT_L and turn on ILMT_H.

In order to avoid function fail. Please don’t turn on ILMT_L and ILMT_H simultaneiously.



Power-up & Operating Guideline

1. RT7238B starts work by providing VIN voltage then turn on EN1 and EN2 switches. In the RT7238B application, the BYP and VOUT of jumper JP3 must always short together and resistor R4 must always be shorted.

2. RT7238C starts work by providing VIN voltage then turn on EN1 switches. In the RT7238C application, the resistor R4 must always be shorted.

3. RT7238D starts work by providing VIN voltage then turn on EN1 switches. In the RT7238D application, the output voltage can be setted by individual resistor R4 and R5. Moreover, the current limt threshold can be chosen through ILMIT_L and ILMIT_H switches after the jumper J2 , resistor R14, R10 and capacitor C18 are shorted.



Schematic

Technical Document Image Preview



Bill of Materials

Reference

Q'ty

Part Number

Description

Package

Manufacture

C3, C4

2

C1608X5R0J475KT000N

4.7µF/6.3V/0603/X5R

0603

TDK

L1

1

7443340100

1µH for RT7238D

2.2µH for RT7238B/C

8 x 8 x 7.5 mm

GOTREND

C6, C9

2

C1608X7R1H104KT000N

0.1µF/50V/0603/X5R

0603

TDK

C8, C10

2

GRM31CR61A226KE19L

22µF/25V/1206/X5R

1206

muRata

C11, C12, C13, C14

4

C3225X5R1E226MT

22µF/25V/1210/X5R

1210

TDK

BYP/EN2/VCC

1

Gold PIN

Gold PIN

Gold PIN

Gold PIN

LDO/VCC/LDO

1

Gold PIN

Gold PIN

Gold PIN

Gold PIN

J1, J2, J3, J4

4

Connector

Connector

Connector

Connector

GND

2

Gold PIN

Gold PIN

Gold PIN

Gold PIN

JP1 ,JP2, J6

3

Jumper

Jumper

Jumper

Jumper

R1, R2, R8, R10, R12, R15, R16

7

Shorted

Shorted

Shorted

Shorted

R3, R7

2

0603 100K 1%

100kΩ/0603/1%

0603

WALSIN

R6, R13

2

0603 360K 1%

1mΩ/0603/1%

0603

WALSIN

R4

1

0603 15K0 1%

Shorted for RT7238B/C

15kΩ/0603/1% for RT7238D (VOUT 1.05V)

0603

WALSIN

R5

1

0603 20K0 1%

20kΩ/0603/1%

0603

WALSIN

SW1

1

SWITCHES

SWITCHES

SWITCHES

SWITCHES

EN1/EN/EN, PG, FB/FB/ILMIT, BS, LX

5

Test PIN

Test PIN

Test PIN

Test PIN

U1

1

RT7238B/C/D

RT7238B/C/D

UQFN-10L 3x3 (FC)

RICHTEK



PCB Layout

Technical Document Image Preview

Top View (1st layer)

Technical Document Image Preview

PCB Layout—Inner Side (2nd Layer)

Technical Document Image Preview

PCB Layout—Inner Side (3rd Layer)

Technical Document Image Preview

Bottom View (4th Layer)

Title Last Update Share Download
Evaluation Board User Guide 2015/11/10
Bill of Materials 2015/11/10
Gerber File 2015/11/10
Schematic 2015/11/10
RT7238B/RT7238C/RT7238D/RT7238E

8A, 23V, 500kHz 同步降壓型轉換器+3.3V/5V LDO

RT7238B/RT7238C/RT7238D/RT7238E

RT7238B/C/D/E是一款ACOT®(Advanced Constant On-Time)操作模式的同步降壓型DC/DC轉換器。系統操作於ACOT模式下可在廣負載變動範圍內提供良好的暫態回應。RT7238B/C/D/E可操作於輸入電壓從8V至23V。RT7238D的輸出電壓為0.6V至5V可調。

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