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High Efficiency Single Synchronous Buck PWM Controller

EVB_RT8129AGQW

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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.

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.


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



Bench Test Setup Conditions

Headers Description and Placement

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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.



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 :

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Schematic, Bill of Materials & Board Layout

EVB Schematic Diagram

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Bill of Materials

Reference

Qty

Part Number

Description

Package

Manufacture

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

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

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

RT8129

WDFN-10L 3x3

RICHTEK

Z1, Z2, Z3, Z4

4

PAD6

SIP-1P-M



PCB Layout

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Top View (1st layer)

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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)

Title Last Update Share Download
Evaluation Board User Guide 2015/11/10
Bill of Materials 2015/11/10
Gerber File 2015/11/10
Schematic 2015/11/10
RT8129A

High Efficiency Single Synchronous Buck PWM Controller

RT8129A

The RT8129A is a high efficiency single 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 automatically operates 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.

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