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

EVB_RT2825GQV(2)

ACTIVE

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 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% V_REF Accuracy

Key Performance Summary Table

Key Features	Evaluation Board Number : PCB098_V1
Default Input Voltage	12V
Max Output Current	I_OUT1 = 5A; I_OUT2 = 5A
Default Output Voltage	V_OUT1 = 1.8V; V_OUT2 = 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

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 < V_IN < 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 (R_UP = R7, R8; R_DOWN = R6, R9) between VOUT and GND with the midpoint connected to FB. The output is set by the following formula :

Frequency Setting

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

Schematic, Bill of Materials & Board Layout

EVB Schematic Diagram

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

PCB Layout

Top View (1^st layer)

PCB Layout—Inner Side (2^nd Layer)

PCB Layout—Inner Side (3^rd Layer)

Bottom View (4^th Layer)

Title	Last Update	Share
Evaluation Board User Guide	2023/07/14	Email RSS Facebook Google+ twitter Linkedin
Bill of Materials	2023/07/14	Email RSS Facebook Google+ twitter Linkedin
Schematic	2023/07/14	Email RSS Facebook Google+ twitter Linkedin
Gerber File	2023/07/14	Email RSS Facebook Google+ twitter Linkedin

RT2825

The RT2825 features two synchronous wide input range high efficiency buck converters that cab deliver up to 5A/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.

Please confirm with our distributor or sales representative for actual stock status.