RT7272BGSP Evaluation Board Table of Contents

RT7272BGSP
Evaluation Board
Purpose
The RT7272B 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
RT7272B 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 ............................................................................................. 2
Bench Test Setup Conditions ......................................................................................................... 3
Headers Description and Placement .......................................................................................... 3
Test Points.................................................................................................................................. 3
Power-up & Measurement Procedure ........................................................................................ 4
Output Voltage Setting ............................................................................................................... 4
Schematic, Bill of Materials and Board Layout ............................................................................... 5
EVB Schematic Diagram ............................................................................................................ 5
Bill of Materials ........................................................................................................................... 6
EVB Layout................................................................................................................................. 7
Other Technical Information ......................................................................................................... 10
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RT7272BGSP
Evaluation Board
Introduction
General Product Information
General Description
The RT7272B 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 150mΩ 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 RT7272B provides complete protection functions such as input
under voltage lockout, output under voltage protection, over current protection and thermal shutdown.
The RT7272B is available in the thermal enhanced SOP-8 (Exposed Pad) package.
Features
 4.5V to 36V Input Voltage Range
 3A Output Current
 Internal N-MOSFETs
 Current Mode Control
 Fixed Frequency Operation : 500kHz
 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
 Adjustable Current Limit
Key Performance Summary Table
Key features
Default Input Voltage
Max Output Current
Default Output Voltage
Default Marking & Package Type
Operation Frequency
Other Key Features
Protection
UG7272BGSP-00
April
2014
Evaluation board number: PCB001_V1
12V
3A (OCP level set to 5.5A typical by RLIM = 137kΩ)
3.3V
RT7272BGSP, SOP-8 (Exposed Pad)
Steady 500kHz at PWM
4.5V to 36V Wide Input Voltage Range
Adjustable Current Limit 2A to 6A
PSM/ PWM Auto Switched.
Over Current Protection &
Output Under-Voltage-Protection (hiccup mode)
Input Under-voltage Lock-out, Thermal Shutdown
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RT7272BGSP
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 [email protected].
Test Points
The EVB is provided with the test points and pin names listed in the table below.
Test point/
Pin name
VIN
Signal
Comment (expected waveforms or voltage levels on test points)
Input voltage
Input voltage range= 4.5V to 36V
Default output voltage = 3.3V
VOUT
Output voltage
Output voltage range= 0.8V to 30V
(see ‘’ Output Voltage Setting’’ section for changing output voltage level)
SW
Switching node test point
EN
Enable test point
BOOT
Boot strap supply test point
Floating supply voltage for the high-side N-MOSFET switch
MODE
RLIM test point
Current limit setting point
GND
Ground
Ground
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April
2014
SW waveform
Enable signal. EN is automatically pulled high (by R4) to enable operation.
Connect EN low to disable operation.
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RT7272BGSP
Evaluation Board
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:
VOUT = 0.8 x (1 +
R1
)
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 RT7272B IC datasheet.
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RT7272BGSP
Evaluation Board
Schematic, Bill of Materials and Board Layout
EVB Schematic Diagram
TP4
BOOT
D2
U1
NF
GP1
8
SOP-8(Exposed Pad)
VIN
BOOT
2
TP3
SW
0.1uF
100k
C11
0.1uF
TP1
EN
SW
R4
10uF
C3
10uF
C2
GND
GP3
L1
1
4.7uH
FB
6
0.1uF
C5
C6
C12
22uF
GP4
GND
2.7nF
R3
TP2
MODE
24k
22uF
R2
COMP
4,9
RLIM
137k
RLIM
NF
C7
7
GND
RCAMP
75k
R1
0
5
R5
0
NF
NF
C9
NF
D1
NF
GND
C13
R6
EN
C4
VOUT
3
13k
NF
C8
GP2
C1
VIN
C1, C2: 10μF/50V/X5R, 1206, TDK C3216X5R1H106K
C4, C5: 22μF/16V/X5R, 1210, Murata GRM32ER61C226K
L1: 4.7μH WE74437368047, DCR=15mΩ
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RT7272BGSP
Evaluation Board
Bill of Materials
Reference
Qty
Part number
Description
Package
Manufacture
U1
1
RT7272BGSP
DC/DC Converter
PSOP-8
Richtek
C1, C2
2
C3216X5R1H106K160AB
1206
TDK
C4, C5
2
GRM32ER61C226KE20#
1210
Murata
C7
1
0603B272K500
0603
WALSIN
C3, C6, C11
3
C1608X7R1H104K080AA
0603
TDK
C8,C9,C12,C13
0
L1
1
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
RLIM
1
137kΩ/±1%, Resistor
0603
TP
4
Test Pin
GP
4
Golden Pin
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April 2014
10μF/±10%/50V/X5R
Ceramic Capacitor
22μF/±10%/16V/X5R
Ceramic Capacitor
2.7nF/±10%/50V/X7R
Ceramic Capacitor
0.1μF/±10%/50V/X7R
Ceramic Capacitor
Not Installed
WE74437368047
4.7μH/19A/±20%,
DCR=15mΩ, Inductor
0603
11mmx10mmx3.8mm
WE
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RT7272BGSP
Evaluation Board
EVB Layout
st
Top View (1 layer)
Bottom View (4th Layer)
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April 2014
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RT7272BGSP
Evaluation Board
st
Component Placement Guide—Component Side (1 layer)
PCB Layout—Component Side (1st Layer)
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RT7272BGSP
Evaluation Board
PCB Layout—Inner Side (2nd Layer)
PCB Layout—Inner Side (3rd Layer)
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RT7272BGSP
Evaluation Board
Component Placement Guide—Bottom Side (4th Layer)
PCB Layout—Bottom Side (4th layer)
Other Technical Information
 For more information, please find the related datasheet or application notes from the Richtek website
http://www.richtek.com
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