EVB RT7249GQW-00 EN

RT7249GQW
Evaluation Board
your power partner.
3A, 18V Synchronous Step-Down Converter with Adjustable
Current Limited Power Switch
Purpose
The RT7249 is a current mode step-down converter with the input voltage range from 4.5V to 18V and provides 3A
outputcurrent. This document explains the function and use of the RT7249 evaluation board (EVB), and provides
information to enable operation, modification of the evaluation board and circuit to suit individual requirements.
Table of Contents
Purpose ................................................................................................................................................................. 1
Introduction............................................................................................................................................................ 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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2016
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RT7249GQW
Evaluation Board
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Introduction
General Product Information
The RT7249 is a high efficiency, monolithic synchronous step-down DC/DC converter with a power switch.The buck
converter can deliver up to 3A output current from 4.5V to 18V input supply. The RT7249’s current-mode
architecture and external compensation allow the transient response to be optimized over a wide input range and
loads. Cycle-by-cycle current limit provides protection against shorted output and soft-start eliminates input current
surge during start-up. The RT7249 also provides under-voltage protection and thermal shutdown. PWM frequency is
adjustable by the ROSC pin and Power Switch current limit can also be adjusted by the RLIM pin. The low current
(<3µA) in shutdown mode provides output disconnection, enabling easy power management in bettery-powered
systems. The RT7249 is available in the WQFN-16L 4x4 package.
Product Feature

Buck Regulator
4.5V to 18V Input Voltage Range
3A Output Current
Internal N-Chanel MOSFETs
Current Mode Control

Adjustable PWM Frequency
Adjustable Output from 0.8V to 15V
Adjustable Soft-Start Time
Stable with Ceramin Output Capactiors
Cycle-by-Cycle Current Limit
Input Under-Voltage Lockout
Output Under-Voltage Protection
Thermal Shutdown
Power Switch
±15% Current-Limit Accuracy at 1.2A
Adjustable Current Limit : 75mA to 2580mA
Meet USB Current-Limiting Requirements
Reverse Input-Output Voltage Protection
Built Soft-Start
120mΩ High-Side MOSFET
Operating Range : 2.5V to 5.5V
Key Performance Summary Table
Key Features
Evaluation Board Number : PCB067_V1
Default Input Voltage
12V
Max Output Current
3A
Default Output Voltage
5V
Default Marking & Package Type
RT7249GQW, WQFN-16L 4x4
Operation Frequency
500kHz Switching Frequency
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2016
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RT7249GQW
Evaluation Board
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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
Signal
Comment (expected waveforms or voltage levels on test points)
VIN
Input voltage
Power Input. Supply voltage range is from 4.5V to 18V. Must bypass
with a suitable large ceramic capacitor.
PGND
Ground
Power Ground. The exposed pad must be soldered to a large PCB
and connected to PGND for maximum thermal dissipation.
AGND
Ground
Analog Ground.
SS
Soft-Start
Soft-Start Time Setting. SS controls the soft-start period. Connect a
capacitor from SS to GND to set the soft-start period. An internal
current source (6μA) charges 0.1μF capacitor and sets the soft-start
period to 13.5ms. If SS is floating, the SS charge current will decrease
to 1/128μA and charge 30pF capacitor to set the soft-start period to
4ms.
COMP
Compensation Node
Compensation Node. COMP is used to compensate the regulation
control loop.Connect a series RC network from COMP to GND. In
some cases, an additional capacitor from COMP to GND is required.
ROSC
Frequency Setting
Switching Frequency Setting.
RLIM
Current Limit Setting
Current Limit Setting. Switch current limit threshold can be set by an
external resistor. Current limit value is from 75mA to 2580mA. The
value of 10kΩ ≤ RILIM ≤ 210kΩ is recommended.
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Test point/
Pin name
Signal
Comment (expected waveforms or voltage levels on test points)
EN_SW
Enable Power Switch
test pin
Enable Control Input for Power Switch.
FAULT
FAULT test point
Active-Low Open-Drain Output. Asserted during over current, over
temperature, or reverse voltage conditions.
SW_OUT
Power Switch Output
Power Switch Output.
SW_IN
Power Switch Input
Power Switch Input. Supply voltage range is from 2.5V to 5.5V.
FB
Feedback Voltage
Feedback Voltage Input. This pin is connected to the converter output.
It is used to set the output of the converter to regulate the desired
value via an resistive divider.
LX
Switch Node test pin
Switch Node. Output of the internal high-side MOSFET. Connect this
pin to external low-side N-MOSFET, inductor and bootstrap capacitor.
BOOT
BOOT Node test pin
Bootstrap Supply for High-Side Gate Driver. Connect a 1μF ceramic
capacitor between the BOOT and LX pins.
V5V
V5V test pin
BG Driver Bias Supply. Decouple with a 1μF X5R/X7R ceramic
capacitor between the V5V and GND pins.
EN
Enable test pin
Enable Control Input for Buck Converter. A logic-high enables the
converter; a logic-low forces the device into shutdown mode.
Power-up & Measurement Procedure
1. Set the jumper at JP1 to connect terminals 1 and 2, connecting Vout to SW_IN
2. Apply a 12V nominal input power supply to the VIN and GND terminals.
3. Connect an external load up to 6A 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 External Input and GND with the midpoint
connected to VREFIN. The output is set by the following formula :
VOUT = VFB
R2
(R1 + R2)
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Schematic, Bill of Materials & Board Layout
EVB Schematic Diagram
Bill of Materials
Reference
Qty
Part Number
Description
Package
Manufacture
C1, C2, C10
3
UMK325BJ106MM
10µF/X5R/50V/1206
C-1206
TAIYO
YUDEN
C3, C7, C9
3
C1608X7R1H104KT000N
0.1µF/X7R/50V/0603
C-0603
TDK
C4, C5, C8
3
C3225X5R1E226MT
22µF/X5R/25V/1210
C-1210
TDK
C6
1
C11, C16
2
C-0603
WALSIN
C12, C19
2
C14, C15
2
C-0603
TDK
C17
1
C18, C20
2
C-0603
TDK
C3_1
1
NC
GP1
1
EN
GP3, GP4, GP8
3
GND
GP5
1
Vin
EVB_RT7249GQW-00
April
NC/1210
0603B472K500
4.7nF/X7R/50V/0603
NC/0603
C1608X5R1E105KT000E
1µF/X5R/25V/0603
NC
C1608X7R1H104KT000N
2016
0.1µF/X7R/50V/0603
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Reference
Qty
Part Number
Description
Package
Manufacture
GP6
1
Vout
GP7
1
SW_OUT
GP9
1
SW_IN_S
GP10
1
SS
GP14
1
SW
GP15
1
V5V
GP16
1
nFAULT
GP17
1
BOOT
GP11
1
RSOC
GP12
1
RLIM
GP13
1
ENSW
JP1
1
SW_IN
J1
1
Vin, GND
L2
1
NR8040T4R7N
4.7µH
R1
1
0603 40K2 1%
40.2k/0603
R-0603
R2
1
7.68k/0603
R-0603
R3
1
20k/0603
R-0603
R4
1
53.6k/0603
R-0603
R5
1
10k/0603
R-0603
R6, R7, R8
3
100k/0603
R-0603
U1
1
DC/DC Converter
WQFN-16L
4x4
Z1, Z2, Z3, Z4
4
SIP-1P-M
Z11, Z12, Z13, Z14
4
FK_1
EVB_RT7249GQW-00
April
RT7249GQW
2016
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YUDEN
RICHTEK
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RT7249GQW
Evaluation Board
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PCB Layout
Top View (1st layer)
PCB Layout—Inner Side (2nd Layer)
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2016
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RT7249GQW
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PCB Layout—Inner Side (3rd Layer)
Bottom View (4th Layer)
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2016
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RT7249GQW
Evaluation Board
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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 TO
BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL
DAMAGES.
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2016
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