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RT6248BHGQUF Step-Down Converter Evaluation Board

EVB_RT6248BHGQUF

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The RT6248B is an advanced constant on-time (ACOT) mode synchronous buck converter. The main control loop of the RT6248B using an advanced constant on-time (ACOT) mode control which provides a very fast transient response. The RT6248B operates from 4.5V to 18V input voltage, the output voltage can be programmed between 0.6V to 5.1V.

Purpose

The RT6248B is an advanced constant on-time (ACOT) mode synchronous buck converter with the input voltage range from 4.5V to 18V and provides 8A output current. This document explains the function and use of the RT6248B evaluation board (EVB), and provides information to enable operation, modification of the evaluation board and circuit to suit individual requirements.


Introduction

General Product Information

The RT6248B is an advanced constant on-time (ACOT) mode synchronous buck converter. The main control loop of the RT6248B using an advanced constant on-time (ACOT) mode control which provides a very fast transient response. The RT6248B operates from 4.5V to 18V input voltage, the output voltage can be programmed between 0.6V to 5.1V.


Product Feature

  • Input Voltage Range : 4.5V to 18V
  • 8A Output Current
  • ACOT™ Mode Performs Fast Transient Response
  • ACOT™ Architecture to Enable All MLCC Output Capacitor Usage
  • Fixed 500kHz Switching Frequency
  • High Efficient Internal Power MOSFET Switch 24mΩ (High-Side) and 12mΩ (Low-Side)
  • Adjustable Output Voltage from 0.6V to 5.1V
  • Pre-biased Soft-Start
  • Cycle-by-Cycle Over-Current Protection
  • Input Under-Voltage Lockout
  • Thermal Shutdown Protection
  • Output Over/Under-Voltage Protection

Key Performance Summary Table

Key Features

Evaluation Board Number: PCB091_V1

Default Input Voltage

12V

Max Output Current

8A

Default Output Voltage

3.3V

Default Marking & Package Type

RT6248BHGQUF, UQFN-12HL 3x3 (FC)

Operation Frequency

Steady 500kHz at all loads



Bench Test Setup Conditions

Headers Description and Placement

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Carefully inspect all the components used in the EVB according to the following Bill of Materials table, and then make sure all the components are undamaged and correctly installed. If there is any missing or damaged component, which may occur during transportation, please contact our distributors or e-mail us at 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 4.5V to 18V Input Voltage. Must bypass with a suitable large ceramic capacitor at this pin.

EN

Enable test point

Enable control. Pull this pin high to turn on the Buck. Do not leave this pin floating.

GND

Ground

Ground.

PGOOD

Power good test point

Power good Indicator. Open drain output when the output voltage is within 90% to 120% of regulation point.

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 = 0.6V.

VCC

Internal regulator output

5V linear regulator Output for Internal Control Circuit. A capacitor (typical 1µF) should be connected to AGND. Don’t connect to external Load.

BOOT

Bootstrap supply test point

Bootstrap supply for high-side gate driver. Connect a 0.1µF ceramic apacitor between the BOOT and SW pins.

LX

Switch node test point

Connect this pin to an external L-C filter.

BYP

Bypass test point

Bypass input for the internal LDO. BYP is externally connected to the output of switching regulator. When the BYP voltage rises above the bypass switch turn-on threshold, the LDO regulator shuts down and the VCC pin is connected to the BYP pin through an internal switch.

ILIMT

Current limit seeting

Current limit setting pin. The current limit is set to 8A, 10A or 12A when this pin is pull low, floating or pull high respectively.



Power-up & Measurement Procedure

1. Connect input power (4.5V < VIN < 18V) and input ground to VIN and GND test pins respectively.

2. Connect positive end and negative terminals of load to VOUT and GND test pins respectively.

3. Set the jumper at J7 to connect terminals 2 and 3, connecting EN to VIN through resistor REN, to enable operation.

4. Verify the output voltage (approximately 3.3V) between VOUT and GND.

5. Connect an external load up to 8A to the VOUT and GND terminals and verify the output voltage and current.


Output Voltage Setting

Set the output voltage with the resistive divider (R4, R5) 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

Manufacturer

U1

1

RT6248BHGQUF

DC-DC Converter

UQFN-12HL 3x3 (FC)

RICHTEK

C3

1

C1608X5R0J475KT

4.7µF/6.3V/0603

C-0603

TDK

C4

1

C1608X5R1E105KT000E

1µF/25V/X5R/0603

C-0603

TDK

C6, C9, C15, C16

4

C1608X7R1H104KT000N

0.1µF/50V/X7R/0603

C-0603

TDK

C7

1

0603N680J500

68pF/50V/NPO/0603

C-0603

WALSIN

C8, C10

2

UMK325BJ106MM

10µF/50V/X5R/1210

C-1210

TAIYO YUDEN

C11, C12

2

C3225X5R1E226MT

22µF/25V/X5R/1210

C-1210

TDK

L1

1

7443552150

1.5µH

L-GSCDK104

WE

R3, R19

2

WR06X1003FTL

100k/0603

R-0603

WALSIN

R4

1

RTT039092FTP

90.9k/0603

R-0603

WALSIN

R5

1

WR06X2002FTL

20k/0603

R-0603

WALSIN

R11

1

WR06X3602FTL

36k/0603

R-0603

WALSIN

R12, R15

2

WR06X000PTL

0R/0603

R-0603

WALSIN

R16

1

WR06X7502FTL

75k/0603

R-0603

WALSIN

R18

1

WR06X1002FTL

10k/0603

R-0603

WALSIN



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 2017/12/13
Bill of Materials 2017/12/13
Gerber File 2017/12/13
Schematic 2017/12/13
RT6248B

18V, 8A, 500kHz ACOT™ Synchronous Step-Down Converter

RT6248B

The RT6248B is a simple, easy-to-use, 8A synchronous step-down DC-DC converter with an input supply voltage range of 4.5V to 18V. The device build-in an accurate 0.6V reference voltage and integrates low RDS(ON) power MOSFETs to achieve high efficiency in a UQFN-12HL 3x3 package. The RT6248B adopts Advanced Constant On-Time (ACOTTM) control architecture to provide an ultrafast transient response with few external components and to operate in nearly constant switching frequency over the line, load, and output voltage range. The RT6248B operates in Forced PWM that helps meet tight voltage regulation accuracy requirements. The RT6248B senses both FETs current for a robust over-current protection. It features cycle-by-cycle current limit protection and prevent the device from the catastrophic damage in output short circuit, over current or inductor saturation. A built-in soft-start function prevents inrush current during start-up. The device also includes input under-voltage lockout, output under-voltage protection, over-voltage protection, and over-temperature protection (thermal shutdown) to provide safe and smooth operation in all operating conditions. The RT6248B is offered in a UQFN-12HL 3x3 (FC) package.

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