RT8129AGQW
Evaluation Board
your power partner.
High Efficiency Single Synchronous Buck PWM Controller
Purpose
The RT8129A integrates a Constant-On-Time (COT) PWM controller and MOSFET driver so that the external circuit
is easily designed and the components are reduced.
The controller provides the PWM signal which relies on the FB voltage comparing with internal reference voltage.
The synchronous UGATE driver is turned on at the beginning of each cycle. After the internal one-shot timer expires,
the UGATE driver will be turned off. The pulse width of this one-shot is determined by the controller's input voltage
and the output voltage to keep the frequency fairly constant over the input voltage and output voltage range. Another
one-shot sets a minimum off-time.
Table of Contents
Purpose ................................................................................................................................................................. 1
Introduction............................................................................................................................................................ 2
Key Performance Summary Table .......................................................................................................................... 2
Bench Test Setup Conditions ................................................................................................................................. 3
Schematic, Bill of Materials & Board Layout ........................................................................................................... 4
More Information................................................................................................................................................... 11
Important Notice for Richtek Evaluation Board ...................................................................................................... 11
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Introduction
General Product Information
The RT8129A is a high efficiency singl phase synchronous buck controller with 5V/12V supply voltage. The
RT8129A integrates a Constant-On-Time (COT) PWM controller and a MOSFET drivers with internal bootstrap
diodes, which is specifically designed to improve converter efficiency at light load condition. At light load condition, it
automaticallyoperates in the diode emulation mode to reduce switching frequency and improve conversion
efficiency. Other features include power good indication, enable/disable control and internal soft-start function. The
RT8129A also provide protection functions including Over Voltage Protection (OVP), Under Voltage Protection
(UVP), current limit and thermal shutdown.
This device uses lossless low-side MOSFET RDS(ON) current sense technique for current limit with adjustable
threshold set by connecting a resistor between the LGATE/OCSET and GND.
With above functions, the RT8129A provides customers a cost-effective solution for high efficiency power
conversion. The RT8129A is available in the WDFN-10L 3x3 package.
Product Feature
Wide Input Voltage Range : 2.5V to 25V
High Light Load Efficiency
Integrated High Driving Capability N-MOSFET Gate
Drivers and Embedded Switching Boot Diode
Single IC Supply Voltage : 4.5V to 13.2V
Power-Good Indicator
Enable/Disable Control
Internal Soft-Start
Programmable Current Limit Threshold
Under Voltage Protection
Over Voltage Protection
Thermal Shutdown
Key Performance Summary Table
Key Features
Evaluation Board Number : PCB047_V1
Input Voltage Range
2.5V to 25V
Max Output Current
Programmable
Default Output Voltage
1.5V
Default Marking & Package Type
RT8129AGQW, WDFN-10L 3x3
Operation Frequency
300kHz
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Bench Test Setup Conditions
Headers Description and Placement
Top View
Bottom View
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
Signal
Comment (expected waveforms or voltage levels on test points)
VIN
Input voltage
Power input. Support 2.5V to 25V Input Voltage. Must bypass with a
suitable large ceramic capacitor at this pin.
COMP
Enable test point
High = Enable.
GND
Ground
Ground.
FB
Feedback voltage input
The pin is used to set the output voltage of the converter to regulate to
the desired voltage via a resistive divider. Feedback reference = 0.8V.
VCC
Supply voltage input
5V bias supply input. Connect a 4.7µF capacitor to ground
BOOT
Bootstrap supply test
point
Bootstrap supply for high-side gate driver. Connect a 0.1µF ceramic
capacitor between the BOOT and PHASE pins.
PHASE
Switch node test point
Connect this pin to an external L-C filter.
UG
High-side switch node
test point
High-side MOSFET gate driver output. Connect this pin to the Gate of
high-side MOSFET.
LG
Low-side switch node
test point
Low-side MOSFET gate driver output. Connect this pin to the Gate of
low-side MOSFET.
PGOOD
Power good indication
test point
The PGOOD voltage goes high to indicate the output voltage is in
regulation.
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Power-up & Measurement Procedure
1. Connect input power (2.5V < VIN < 25V and 4.5V < VCC < 13.2V).
2. Connect positive end and negative terminals of load to VOUT and GND test pins respectively.
3. EN pin is internal high, let JP1 open (JP1 short will turn off IC).
4. Verify the output voltage (VOUT approximately 1.5V, and FB approximately 0.8V) between VOUT to GND, and
FB to GND.
5. Connect an external load up to 10A to the VOUT and GND terminals and verify the output voltage and current.
Output Voltage Setting
Set the output voltage with the resistive divider (R8, R10) between VOUT and GND with the midpoint connected to
FB. The output is set by the following formula :
VOUT VFB x (1
R8
)
R10
Schematic, Bill of Materials & Board Layout
EVB Schematic Diagram
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Bill of Materials
Reference
Qty
Part Number
Description
Package
AD7
1
BAT54A
BAT54A
SOT-23_123
C1
1
1µF/50V
C-0805
C2
1
0.1µF
C-0603
C3
1
22pF
C-0603
C4
1
0.22µF/50V
C-0603
C5, C17, C18
3
10µF/16V
C-1206_3-3
C6
1
1µF/16V
C-1206_3-3
C7, C14
2
470µF/16V
EC-2P/10
C8, C9, C15
3
10µF/6.3V
C-0805
C10, C11, C16
3
820µF/2.5V
EC-2P_8_1
C12
1
6.8nF
C-0603
C13
1
2.2nF
C-0603
C19, C20, C21, C22, C23,
C24, C43, C44, C45, C57
10
NC
C-0805
C25, C26
2
NC
EC-2P_8_1
C27, C28, C29
3
NC
c-2512
C30, C31, C32
3
NC
C-0603
C46
1
0.01µF
C-0603
D1
1
1N4148
D-0805_2-3368
FK1, FK2, FK3, FK4
4
SIP-1P-TP
FK_1
GP1
1
VCC
SIP-1P-GP
GP2
1
EXT_BOOT
SIP-1P-GP
GP3, GP4, GP5
3
GND
SIP-1P-GP
GP6
1
BOOT
SIP-1P-GP
GP7
1
VIN
SIP-1P-GP
JP1, JP2
2
SIP-2P
SIP-2P
J1, J2, J3, J4
4
NC
sip-1p_p441d165
J12, J13, J19, J20
4
NC
SIP-4P-PW-2
L1
1
NC
L-2P/387
L2
1
1µH
L-GSDRH127
L3
1
NC
l-2p/9.82
L4
1
NC
L-GMAR-V3R2-151311
Q1, Q6
2
IPD09N03LA
IPD09N03LA
DPAK_GDS
Q2, Q7
2
IPD06N03LA
IPD06N03LA
DPAK_GDS
Q3, Q4, Q8, Q9
4
NC
Q-TDSON-8
Q5
1
2N7002
SOT-23_123
R1, R5
2
2.2
R-0603
R2
1
22K
R-0603
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Reference
Qty
Part Number
Description
Package
R3
1
13K
R-0603
R4, R8
2
1K
R-0603
R6, R14
2
10K
R-0603
R7, R13, R19, R20, R21
5
0
R-0603
R9
1
75
R-0603
R10
1
1.1K
R-0603
R11
1
1
R-0603
R12
1
20K
R-0603
R15, R22
2
NC
R-0603
R16, R17, R18
3
short
CP-0805C
TP6
1
VOS
SIP-1P-TP
TP7
1
PGOOD
SIP-1P-TP
TP8
1
PHASE
SIP-1P-TP
TP9
1
UG
SIP-1P-TP
TP10
1
LG
SIP-1P-TP
TP11
1
COMP
SIP-1P-TP
TP12
1
FB
SIP-1P-TP
U1
1
RT8129
WDFN-10L 3x3
Z1, Z2, Z3, Z4
4
PAD6
SIP-1P-M
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RT8129AGQW
Evaluation Board
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PCB Layout
Top View (1st layer)
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Evaluation Board
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PCB Layout—Inner Side (2nd Layer)
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PCB Layout—Inner Side (3rd Layer)
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Bottom View (4th Layer)
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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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