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Richtek

4.5V to 18V, 5A/5A Dual Synchronous Step-Down Converter

EVB_RT2825GQV(2)

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EOL: Richtek has discontinued the production of the device.

The RT2825 features two synchronous wide input range high efficiency buck converters that can deliver up to 5A output current from a 4.5V to 18V input supply. The converters are designed to simplify its application while giving the designer the option to optimize their usage according to the target application.

Purpose

The RT2825 is a current mode step-down converter with the input voltage range from 4.5V to 18V and provides two channels 5A output current. This document explains the function and use of the RT2825 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 RT2825 features two synchronous wide input range high efficiency buck converters that can deliver up to 5A output current from a 4.5V to 18V input supply. The converters are designed to simplify its application while giving the designer the option to optimize their usage according to the target application.

The converters can operate in 5V, 9V, 12V or 15V systems and have integrated power transistors. The RT2825's current mode architecture allows the transient response to be improved. Cycle-by-cycle current limit provides protection against shorted outputs.

Each converter features enable pin that allows a delayed start-up for sequencing purposes, soft-start pin that allows adjustable soft-start time by choosing the soft-start capacitor, and a current limit (RLIMx) pin that enables designer to adjust current limit by selecting an external resistor and optimize the choice of inductor. The COMP pin allows optimizing transient versus dc accuracy response with a simple RC compensation.

The switching frequency of the converters can either be set with an external resistor connected to ROSC pin or can be synchronized to an external clock if needed. The switching regulators are designed to operate from 200kHz to 1MHz. The converters operate with 180° phase between two channels to minimize the input filter requirements.

The RT2825 also features a low power mode enabled by an external signal, which allows for a reduction on the input power supplied to the system when the host processor is in stand-by (low activity) mode.

The RT2825 is available in a VQFN-36L 6x6 package.


Product Feature

  • Wide Input Supply Voltage Range : 4.5V to 18V
  • Fully Integrated Dual-Buck Converter, Up to 5A/5A
  • Adjustable Switching Frequency 200kHz to 1MHz Set by External Resistor or SYNC Signal
  • Dedicated Enable/Soft-Start for Each Buck
  • Current Mode Control with Simple Compensation Circuit
  • Adjustable Cycle-by-Cycle Current Limit Set by External Resistor
  • Over-Temperature Protection
  • Power Good Indicator
  • Discontinuous Operating Mode at Light Load when LOWP pin = L
  • 1% VREF Accuracy


Key Performance Summary Table

Key Features

Evaluation Board Number : PCB098_V1

Default Input Voltage

12V

Max Output Current

IOUT1 = 5A; IOUT2 = 5A

Default Output Voltage

VOUT1 = 1.8V; VOUT2 = 1.8V

Default Marking & Package Type

RT2825GQV(2), VQFN-36L 6x6

Operation Frequency

Adjustable Frequency. Default = 400kHz



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

Signal

Comment (expected waveforms or voltage levels on test points)

VIN1, VIN2

Power Input Voltage Test Point

To monitor the voltage of input capacitors.

VINR

Signal Power Input Test Point

To monitor the voltage of internal control circuit.

EN1, EN2

Enable Test Point

To monitor enable control input voltage of CH1 and CH2. A low level signal on this pin disables it. If this pin is left floating, a weak internal pull-up will allow automatic enables.

LOWP

Low Power Mode Test Point

To monitor the control voltage of LOWP pin.

PG1, PG2

Power Good Test Point

To monitor power good signal of CH1 and CH2.

RLIM1, RLIM2

Current Limit Test Point.

To monitor the voltage of RLIM1/RLIM2 pins.

BOOT1, BOOT2

Bootstrap Supply Test Point

To monitor the voltage of BOOT1/BOOT2 pins.

LX1, LX2

Switch Node Test Point

To monitor the switching voltage of CH1 and CH2.

SS1, SS2

Soft-Start Test Point

To monitor the SS voltage of CH1 and CH2.

OSC

Oscillator Setting Test Point

To monitor the voltage of OSC pin.

VOUT1, VOUT2

Output Voltage Test Point.

To monitor the output voltage of CH1 and CH2.

GND

Ground

Ground.

PVCC

Internal Regulator Output Test Point.

To monitor the 5V power supply output voltage of PVCC pin.


Power-up & Measurement Procedure

1. Connect input power (4.5V < VIN < 18V) and input ground to VIN12 and GND respectively.

2. Connect positive end and negative terminals of load to VOUT1/VOUT2 and VOUT1_PGND/VOUT2_PGND respectively.

3. There is a 3-pin header “EN” for enable control. To use a jumper at “H” option to tie EN test pin to input power VIN via a 100k resistor for enabling the device. Inversely, to use a jumper at “L” option to tie EN test pin and ground GND for disabling the device. Let EN floating will also enable control.

4. Verify the output voltage (approximately 1.8V) between VOUT1/VOUT2 and GND.

5. Connect an external load up to 5A to the VOUT1/VOUT2 and GND terminals and verify the output voltage and current.


Output Voltage Setting

Set the output voltage with the resistive divider (RUP = R7, R8; RDOWN = R6, R9) between VOUT and GND with the midpoint connected to FB. The output is set by the following formula :

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自動產生的描述


Frequency Setting

Set the converter frequency with the oscilator resistor (ROSC = R11) between OSC and GND. The practical switching frequency ranges from 200kHz to 1MHz. Determine the ROSC resistor value by examining the curve in below Figure.

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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

RT2825GQV(2)

DC-DC Converter

VQFN-36L 6x6

RICHTEK

C1, C28

2

0603B822K500CT

8.2nF/50V/X7R

C-0603

WALSIN

C2, C25

2

C1608X7R1H103KT000N

10nF/50V/X7R

C-0603

TDK

C3, C4, C26, C27

4

0603B181K500CT

180pF/50V/X7R

C-0603

WALSIN

C5

1

TMK107BJ105KA-T

1µF/25V/X5R

C-0603

TAIYO YUDEN

C6, C7, C8, C21, C22

5

GRM31CR71E106KA12L

10µF/25V/X7R

C-1206

muRata

C9, C10, C11, C12, C17, C18, C19, C20, C31, C32

10

GRM31CR61C226KE15L

22µF/16V/X5R

C-1206

muRata

C13, C15

2

GRM188R71H104KA93D

100nF/50V/X7R

C-0603

muRata

C23, C24

2

C3216X5R1H106K160AB

10µF/50V/X5R

C-1206

TDK

L1, L2

2

7443330220

2.2µH

L-8-4x7-9

WURTH ELEKTRONIK

R1, R4, R5, R10, R11, R14

6

WR06X1003FTL

100k

R-0603

WALSIN

R2, R13

2

WR06X6042FTL

60.4k

R-0603

WALSIN

R3, R12

2

RTT032101FTP

2.1k

R-0603

RALEC

R6, R9

2

WR06X2402FTL

24k

R-0603

WALSIN

R7, R8

2

RTT034752FTP

47.5k

R-0603

RALEC


Measurement Results

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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 2023/07/14
Bill of Materials 2023/07/14
Schematic 2023/07/14
Gerber File 2023/07/14
RT2825
RT2825

RT2825是集成了兩組5A同步Buck轉換器的電源IC,工作電壓範圍為4.5V至18V,為電子系統的設計者提供了優化的電源管理方案。
RT2825的兩組轉換器均可在5V、9V、12V或15V的系統中應用,均集成了功率開關。它們採用電流模式控制架構,瞬態回應特性良好。它們在工作過程中採用逐週期電流限制方式,可在輸出端出現短路現象時提供保護作用。
RT2825的兩組轉換器都含有方便進行時序控制的使能控制端,有可接電容的軟起動端子對啟動過程進行控制,有獨立的電流限制端子 (RLIMx) 可對電流限制閾值進行調節,同時使電感器的選擇更加安全。透過對COMP端外接的RC電路參數的調整,使用者可對轉換器的瞬態回應特性和直流回應的特性進行優化調節。
假如有需要,使用者可通過ROSC端外接電阻的調節對轉換器的開關工作頻率進行調整,也可引入外部時鐘信號實現同步工作。轉換器的最佳工作頻率範圍是200kHz至1MHz,兩組之間的工作相位相差180 °,對輸入濾波器的需求降到了最低程度。
RT2825引入了低功率工作模式,可通過外部信號來啟動,可在主機系統進入待機模式時降低電源輸入端的功率消耗。
RT2825採用VQFN-36L 6x6封裝。

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