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
UG7272BGSP-00
April
2014
www.richtek.com
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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2
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 evb_service@richtek.com.
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
UG7272BGSP-00
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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3
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 (
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