Richtek RT7247AHGSP User manual

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014
www.richtek.com
Purpose
The RT7247A is a high-efficiency current mode synchronous step-down regulator that can deliver up to 2A output
current from a wide input voltage range of 4.5V to 18V. This document explains the function and use of the
RT7247A 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
General Product Information......................................................................................................................2
Key Performance Summary Table.............................................................................................................3
Bench Test Setup Conditions.........................................................................................................................4
Headers Description and Placement .........................................................................................................4
Test Points ................................................................................................................................................. 4
Power-up & Measurement Procedure........................................................................................................ 5
Output Voltage Setting...............................................................................................................................5
Schematic, Bill of Materials and Board Layout ..............................................................................................6
EVB Schematic Diagram............................................................................................................................6
Bill of Materials...........................................................................................................................................7
EVB Layout ................................................................................................................................................ 8
More Information.......................................................................................................................................... 11
Important Notice for Richtek Evaluation Board............................................................................................11

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
2
Introduction
General Product Information
General Description
The RT7247A is a high efficiency, monolithic synchronous step-down DC/DC converter that can deliver up to 2A
output current from a 4.5V to 18V input supply. The RT7247A's current mode architecture and external
compensation allow the transient response to be optimized over a wide range of loads and output capacitors.
Cycle-by-cycle current limit provides protection against shorted outputs and soft-start eliminates input current surge
during start-up. The RT7247A also provides output under voltage protection and thermal shutdown protection. The
low current (<3μA) shutdown mode provides output disconnection, enabling easy power management in
battery-powered systems. The RT7247Ais available in an SOP-8 (Exposed Pad) package.
Features
±1.5% High Accuracy Feedback Voltage
4.5V to 18V Input Voltage Range
2A Output Current
Integrated N-MOSFET Switches
Current Mode Control
Fixed Frequency Operation : 340kHz
Output Adjustable from 0.8V to 15V
Up to 95% Efficiency
Programmable Soft-Start
Stable with Low-ESR Ceramic Output Capacitors
Cycle-by-Cycle Over Current Protection
Input Under Voltage Lockout
Output Under Voltage Protection
Thermal Shutdown Protection

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
3
Key Performance Summary Table
Key features
Evaluation board number: PCB004_V1
Default Input Voltage
12V
Max Output Current
2A
Default Output Voltage
3.3V
Default Marking & Package Type
RT7247AHGSP, PSOP-8 (Exposed Pad)
Operation Frequency
Steady 340kHz at all loads
Other Key Features
4.5V to 18V Input Voltage Range
Programmable Soft-Start
Protection
Output Under-Voltage Protection (hiccup mode):
Cycle-by-cycle Current Limit
Thermal Shutdown

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
4
Bench Test Setup Conditions
Headers Description and Placement
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 [e-mail].
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 18V
VOUT
Output voltage
Default output voltage = 3.3V
Output voltage range= 0.8V to 15V
(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.
BS
Boot strap supply test point
Floating supply voltage for the high-side N-MOSFET switch
SS
Soft-start control test point
Soft start waveform
GND
Ground
Ground

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
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Power-up & Measurement Procedure
1. Apply a 12V nominal input power supply (4.5V < VIN < 18V) 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 2A 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. The output is set by the following formula:
OUT R1 V = 0.8 x (1 + )
R2
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 RT7247AIC datasheet.

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
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Schematic, Bill of Materials and Board Layout
EVB Schematic Diagram
GND
SOP-8(Exposed Pad)U1
BS 1 VIN
2
SW 3
GND
4,9
SS
8
EN
7
COMP 6
FB 5
L1
10uH
C10
0.1uF
TP2
SS
R4
100k
R5
NF
C13
NF
C1
10uF
C2
10uF
C4
22uF
C8
NF
C7
3.3nF
C3
0.1uF
C5
22uF
R1
75k
R2
24k
R3
13k
C6
0.1uF
TP1
EN
C11
0.1uF
C9
NF
D2
NF
D1
NF
VOUT
GP3
GP4
GP1
GP2
GND
VIN TP3
SW
GND
TP4
BS
C12
NF
C1, C2: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K
C4, C5: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K
L1: 10μH TAIYO YUDEN NR8040T100M, DCR=34mΩ

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
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Bill of Materials
Reference
Qty
Part number
Description
Package
Manufacture
U1
1
RT7247AHGSP
DC-DC Converter
PSOP-8
Richtek
C1, C2
2
C3216X5R1H106K160AB
10uF/±10%/50V/X5R
Ceramic Capacitor
1206
TDK
C4, C5
2
GRM32ER61C226KE20#
22uF/±10%/16V/X5R
Ceramic Capacitor
1210
Murata
C7
1
0603B332K500
3.3nF/±10%/50V/X7R
Ceramic Capacitor
0603
WALSIN
C3, C6, C10,C11
4
C1608X7R1H104K080AA
0.1uF/±10%/50V/X7R
Ceramic Capacitor
0603
TDK
C8,C9,C12,C13
0
Not Installed
0603
L1
1
NR8040T100M
10uH/3.1A/±20%,
DCR=34mΩ, Inductor
8mmx8mmx4mm
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
0
Not Installed
0603
D1, D2
0
Not Installed
TP
4
Test Pin
GP
4
Golden Pin

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
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EVB Layout
Top View (1st layer)
Bottom View (2nd Layer)

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
9
Component Placement Guide—Component Side (1st layer)
PCB Layout—Component Side (1st Layer)

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
10
Component Placement Guide—Bottom Side (2nd layer)
PCB Layout—Bottom Side (2nd layer)

RT7247AHGSP
Evaluation Board
UG7247AHGSP-00 July 2014 www.richtek.com
11
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 TO
BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL
DAMAGES.