RT7279GQW
Evaluation Board
Purpose
The RT7279 is a high-performance 700kHz 2A step down regulator with an internal power switch and synchronous
rectifier. This document explains the function and use of the RT7279 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 ........................................................................................................................................ 5
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 ................................................................................................................................... 12
Important Notice for Richtek Evaluation Board ..................................................................................... 12
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RT7279GQW
Evaluation Board
Introduction
General Product Information
General Description
The RT7279 is a high-performance 700kHz 2A step down regulator with an internal power switch and synchronous
rectifier. It features quick transient response using its Advanced Constant On-Time (ACOTTM) control architecture
that provides stable operation with small ceramic output capacitors and without complicated external compensation,
among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 8V.
The proprietary ACOTTM control improves upon other fast response constant on-time architectures, achieving nearly
constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to
transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large
bulk output capacitance. The RT7279 is stable with and optimized for ceramic output capacitors.
With its internal 90mΩ switch and 60mΩ synchronous rectifier, the RT7279 displays excellent efficiency and good
behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-by cycle
current limit, input under-voltage lock-out, externally-adjustable soft-start, output under- and overvoltage protection,
and thermal shutdown provide safe and smooth operation in all operating conditions.
The RT7279 evaluation board uses the RT7279GQW IC in a WDFN-10L3x3 package with an exposed thermal pad.
The IC is also available in a PTSSOP-14 package with an exposed thermal pad.
Features
Fast Transient Response
Steady 700kHz Switching Frequency at All Load
2A Output Current
TM
Advanced Constant On-Time (ACOT
) Control
Optimized for Ceramic Output Capacitors
4.5V to 18V Input Voltage Range
Internal 90mΩ Switch and 60mΩ Synchronous Rectifier
0.765V to 8V Adjustable Output Voltage
Externally-adjustable, Pre-biased Compatible Soft-Start
Cycle-by-Cycle Current Limit
Output Over- and Under-voltage Shut-down
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RT7279GQW
Evaluation Board
Key Performance Summary Table
Key features
Evaluation board number: PCB002_V1
Default Input voltage
12V
Max Output Current
2A
Default Output Voltage
1.05V
Default Marking & Package Type
RT7279GQW (WDFN-10L 3x3)
Operation Frequency
Steady 700kHz at all load
Other Key Features
Advanced constant On-time(ACOT
TM
) control
Power Good
Adjustable Soft-start (external capacitor)
Protection
Over current protection:
Cycle-by-Cycle Current Limit
Hiccup Mode Output Over- and Under-voltage Shut-down
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Evaluation Board
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 evb_service@richtek.com.
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Test Points
The EVB is provided with the test points and pin names listed in the table below.
Test point/
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 = 1.05V
Pin name
Output voltage range = 0.765V to 8V
(see ‘’ Output Voltage Setting’’ section for changing output voltage level)
GND
Ground
Ground reference for the input voltage, output voltage and analog ground
SW
Switching node test point
SW waveform
EN
Enable test point
Enable signal. Drive EN or install a shorting block on Jumper JP1 to
enable operation (shorting 2-3) or disable operation (shorting 1-2).
JP1
Chip enable control
Install jumper or drive EN directly to enable or disable operation
BOOT
Boot strap supply test point
Floating supply voltage for the high-side N-MOSFET switch
SS
Soft-start control test point
Soft start waveform
PVCC
Linear regulator output test
Internal linear regulator output= 5.1V
point
PG
Power good output test
Connected to PVCC through R29, PG voltage is 5.1V when soft-start is
point
complete and the output voltage is in regulation
Power-up & Measurement Procedure
1. Connect a jumper at JP1 terminals 1 and 2, connecting EN to GND, to disable operation.
2. Apply a 12V nominal input power supply (4.5V < VIN < 18V) to the VIN and GND terminals.
3. Set the jumper at JP1 to connect terminals 2 and 3, connecting EN to VIN through resistor R30, to enable
operation.
4. Verify the output voltage (approximately 1.05V) between VOUT and GND.
5. 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 (R23, R28) between VOUT and GND with the midpoint at FB. The
output is set by the following formula:
VOUT = 0.765 x (1 +
R23
)
R28
The installed VOUT capacitors (C11, C12) 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. Installing a small 5pF to
22pF capacitor at C30 (in parallel with R23) may be desirable to improve transient response for higher output
voltages. See the RT7279 IC datasheet for more information.
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Schematic, Bill of Materials and Board Layout
EVB Schematic Diagram
TP6
SW
VIN
GP4
U5 WDFN-10L 3x3
L1
9
10
C7
C9
10uF 10uF
C8
0.1uF
TP4
SS
VIN
SW
VIN
SW
SS
GND
Short
C27
0.1uF
8
TP5
BOOT
C30
NF
R23
8.2k
2
C11
22uF
EN
PG
PVCC
5
10k
R29
3
11
1
GND
R30
100k
GP1
GND
L2
C12
22uF
C10
0.1uF
GP2
GND
TP1
PG
EN
3
2
1
BOOT
FB
C28
3.9nF
JP1
2.0uH
7
NF
4
GP5
GND
VOUT
GP3
CP1
6
TP3
EN
TP2
PVCC
R28
22k
C29
1uF
C7, C9: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K
C11, C12: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K
L1: 2.0μH TAIYO YUDEN NR8040T2R0N, DCR=9mΩ
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RT7279GQW
Evaluation Board
Bill of Materials
Reference
Qty
Part number
Description
Package
Manufacture
U5
1
RT7279GQW
DC/DC Converter
WDFN-10L 3x3
Richtek
C7,C9
2
C3216X5R1H106K160AB
1206
TDK
1210
Murata
0603
WALSIN
0603
TDK
0603
TDK
10μF/±10%/50V/X5R
Ceramic Capacitor
22μF/±10%/16V/X5R
C11,C12
2
GRM32ER61C226KE20#
Ceramic Capacitor
3.9nF/±10%/50V/X7R
C28
1
0603B392K500
Ceramic Capacitor
0.1μF/±10%/50V/X7R
C8,C10,C27
3
C1608X7R1H104K080AA
Ceramic Capacitor
1μF/±10%/25V/X5R
C29
1
C1608X5R1E105K080AC
Ceramic Capacitor
C30
0
Not Installed
0603
L1
1
L2
0
Not Installed
R28
1
22k/±5%, Resistor
0603
R23
1
8.2k/±5%, Resistor
0603
R29
1
10k/±5%, Resistor
0603
R30
1
100k/±5%, Resistor
0603
CP1
1
0 (Short)
JP1
1
3-Pin Header
TP1/2/3/4/5/6
6
Test Pin
GP
5
Golden Pin
2.0μH/6.3A/±30%,
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NR8040T2R0N
April
2014
DCR=9mΩ, Inductor
8mmx8mmx4mm
TAIYO YUDEN
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RT7279GQW
Evaluation Board
EVB Layout
st
Top View (1 layer)
Bottom View (4th Layer)
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RT7279GQW
Evaluation Board
st
Component Placement Guide—Component Side (1 layer)
st
PCB Layout—Component Side (1 Layer)
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RT7279GQW
Evaluation Board
PCB Layout—Inner Side (2
nd
Layer)
rd
PCB Layout—Inner Side (3 Layer)
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RT7279GQW
Evaluation Board
th
Component Placement Guide—Bottom Side (4 Layer)
th
PCB Layout—Bottom Side (4 layer)
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RT7279GQW
Evaluation Board
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.
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