RT7238B/C/D GQUF
Evaluation Board
your power partner.
Synchronous Step-Down Converter’s Evaluation Board for
RT7238 Integrated Chip
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.
Table of Contents
Purpose ................................................................................................................................................................. 1
Introduction............................................................................................................................................................ 2
Application ............................................................................................................................................................. 2
Key Performance Summary Table .......................................................................................................................... 2
Bench Test Setup Conditions ................................................................................................................................. 3
Schematic, Bill of Materials & Board Layout ........................................................................................................... 5
More Information.................................................................................................................................................... 9
Important Notice for Richtek Evaluation Board ....................................................................................................... 9
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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
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Bench Test Setup Conditions
Headers Description and Placement
RT7238B Top View
RT7238B Bottom View
RT7238C Top View
RT7238C Bottom View
RT7238D Top View
RT7238D 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
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Test Points, Jumpers and Switches
The EVB is provided with the test points, jumpers, switches and individual names listed in the table below.
Signal
Test point/ name
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.
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.
JP3
Switches/ name
SW1
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Signal
EN1 voltage
EN2 voltage
ILMT_L voltage
ILMT_H voltage
October 2015
Description (expected waveforms or voltage levels on test points)
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.
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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, Bill of Materials & Board Layout
EVB Schematic Diagram
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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
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PCB Layout
Top View (1st layer)
PCB Layout—Inner Side (2nd Layer)
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PCB Layout—Inner Side (3rd Layer)
Bottom View (4th Layer)
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More Information
For more information, please find the related datasheet or application notes from Richtek website
http://www.richtek.com.
Important Notice for Richtek Evaluation Board
THIS DOCUMENT IS FOR REFERENCE ONLY, NOTHING CONTAINED IN THIS DOCUMENT SHALL BE CONSTRUED AS RICHTEK’S WARRANTY, EXPRESS
OR IMPLIED, UNDER CONTRACT, TORT OR STATUTORY, WITH RESPECT TO THE PRESENTATION HEREIN. IN NO EVENT SHALL RICHTEK BE LIABLE T O
BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL
DAMAGES.
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