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RT2853BHGQW 3A, 18V, 650kHz, ACOT™ Synchronous Step-Down Converter

EVB_RT2853BHGQW

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The RT2853BH are high-performance 650kHz 3A step-down regulators with internal power switches and synchronous rectifiers. The feature quick transient response using Advanced Constant On-Time (ACOT™) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 7V. The proprietary ACOT™ control improves upon other fast response constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. The RT2853BH are stable with and optimized for ceramic output capacitors. With internal 110mΩ switches and 30mΩ synchronous rectifiers, the RT2853BH display excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-bycycle current limit, input under-voltage lock-out, externallyadjustable soft-start, output under- and over-voltage protection, and thermal shutdown provide safe and smooth operation in all operating conditions. The RT2853BH is available in WQFN-16L 3x3 package, with exposed thermal pads.

Purpose

The RT2853BH are high-performance 650kHz 3A step-down regulators with internal power switches and synchronous rectifiers. This document explains the function and use of the RT2853BH 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 RT2853BH are high-performance 650kHz 3A step-down regulators with internal power switches and synchronous rectifiers. The feature quick transient response using Advanced Constant On-Time (ACOT™) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 7V. The proprietary ACOT™ control improves upon other fast response constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. The RT2853BH are stable with and optimized for ceramic output capacitors. With internal 110mΩ switches and 30mΩ synchronous rectifiers, the RT2853BH display excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-bycycle current limit, input under-voltage lock-out, externallyadjustable soft-start, output under- and over-voltage protection, and thermal shutdown provide safe and smooth operation in all operating conditions. The RT2853BH is available in WQFN-16L 3x3 package, with exposed thermal pads.


Product Feature

  • Fast Transient Response
  • Steady 650kHz Switching Frequency
  • Advanced Constant On-Time (ACOTTM) Control
  • Optimized for Ceramic Output Capacitors
  • 4.5V to 18V Input Voltage Range
  • Internal 110mΩ Switch and 30mΩ Synchronous Rectifier
  • 0.765V to 7V Adjustable Output Voltage
  • Externally-adjustable, Pre-biased Compatible Soft-Start
  • Cycle-by-Cycle Current Limit
  • Optional Output Discharge Function
  • With Hiccup Mode Output Over- and Under-voltage Shut-down protection

 

Key Performance Summary Table

Key Features

Evaluation Board Number : PCB033_V1

Input Voltage Range

4.5V to 18V

Max Output Current

3A

Default Output Voltage

1.05V

Default Marking & Package Type

RT2853BHGQW, WQFN-16L 3x3

Operation Frequency

Fixed 650kHz



Bench Test Setup Conditions

Headers Description and Placement

Technical Document Image Preview

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.

EN

Enable test point

Externally pulled high to enable and pulled low to disable this chip. It is internally pulled up to high when the pin is floating.

GND

Ground

The exposed pad must be soldered to a large PCB and connected to GND for maximum power dissipation.

VREG5

Internal Regulator Output

Internal Regulator Output. Connect a 1μF capacitor to GND to stabilize output voltage.

SS

Soft-Start Control

Connect an external capacitor between this pin and GND

to set the soft-start time.

PG

Power good test point

Output of power good indicator.

BOOT

Bootstrap supply test point

Bootstrap supply for high-side gate driver. Connect a capacitor between the BOOT and SW pins.

SW

Switch node test point

Connect this pin to an external L-C filter.



Power-up & Measurement Procedure

1. Apply a 12V nominal input power supply (4.5< VIN < 18V) to the VIN and GND terminals.

2. Set the jumper at JP2 to connect terminals 2 and 3, connecting EN to enable operation.

3. Set the jumper at JP1 to connect terminals 1 and 2, power VCC pin by VIN voltage source.

4. Verify the output voltage (approximately 1.05V) between VOUT and GND.

5. Connect an external load up to 3A to the VOUT and GND terminals and verify the output voltage and current.


Output Voltage Setting

Set the output voltage with the resistive divider (R2, R3) between VOUT and GND with the midpoint connected to FB. The output is set by the following formula :

Technical Document Image Preview



Schematic, Bill of Materials & Board Layout

EVB Schematic Diagram

Technical Document Image Preview



Bill of Materials

Reference

Qty

Part Number

Description

Package

Manufacture

U1

1

RT2853BHGQW

DC/DC Converter

WQFN-16L 3x3

RICHTEK

C2, C6, C8, C12

4

C1608X7R1H104KT000N

0.1μF/50V/X7R

C-0603

TDK

C3, C4

2

GRM31CR71E106KA12L

10μF/25V/X7R

C-1210

MURATA

C5

1

C2012X7R1H105KT

1μF/50V/X7R

C-0805

TDK

C7

1

0603B332K500

3.3nF/50V/X7R

C-0603

WALSIN

C9, C10

2

C3225X5R1E226MT

22μF/25V/X7R

C-1210

TDK

C1, C11, C13, C14, R6, R7

6

NA

L1

1

NR8040T1R4N

1.4µH/7A

8 x 8 x 4 mm

TAIYO YUDEN

R1

1

0603 JUMP

R-0603

WALSIN

R2

1

0603 8K25 1%

8.25k

R-0603

WALSIN

R3

1

0603 22K1 1%

22.1k

R-0603

WALSIN

R4, R5

2

0603 100K 1%

100k

R-0603

WALSIN



PCB Layout

Technical Document Image Preview

Top View (1st layer)

Technical Document Image Preview

PCB Layout—Inner Side (2nd Layer)

Technical Document Image Preview

PCB Layout—Inner Side (3rd Layer)

Technical Document Image Preview

Bottom View (4th Layer)

Title Last Update Share Download
Evaluation Board User Guide 2016/05/11
Bill of Materials 2016/05/11
Gerber File 2016/05/11
Schematic 2016/05/11
RT2853A/RT2853B

3A, 18V, 650kHz, ACOT® Synchronous Step-Down Converter

RT2853A/RT2853B

The RT2853A/B are high-performance 650kHz 3A step-down regulators with internal power switches and synchronous rectifiers. They feature quick transient response using their Advanced Constant On-Time (ACOT®) control architecture that provides stable operation with small ceramic output capacitors and without complicated external compensation, among other benefits. The input voltage range is from 4.5V to 18V and the output is adjustable from 0.765V to 7V.

The proprietary ACOT® control improves upon other fast-response constant on-time architectures, achieving nearly constant switching frequency over line, load, and output voltage ranges. Since there is no internal clock, response to transients is nearly instantaneous and inductor current can ramp quickly to maintain output regulation without large bulk output capacitance. The RT2853A/B are stable with and optimized for ceramic output capacitors.

With internal 110mΩ switches and 30mΩ synchronous rectifiers, the RT2853A/B display excellent efficiency and good behavior across a range of applications, especially for low output voltages and low duty cycles. Cycle-by-cycle current limit, input under-voltage lock-out, externally-adjustable soft-start, output under- and over-voltage protection, and thermal shutdown provide safe and smooth operation in all operating conditions.

The RT2853A and RT2853B are each available in WQFN-16L 3x3 package, with exposed thermal pads.

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