your power partner.
RT2805AGSP
Evaluation Board
RT2805A Step-Down Converter Evaluation Board
Purpose
The RT2805A is a current mode asynchronous step-down converter that achieves excellent load and line regulation.
This document explains the function and use of the RT2805A evaluation board (EVB) and provides information to
enable operation and modification of the evaluation board and circuit to suit individual requirements.
Table of Contents
Purpose ............................................................................................................................................................... 1
Introduction.......................................................................................................................................................... 2
Application ........................................................................................................................................................... 2
Bench Test Setup Conditions ............................................................................................................................... 3
Step-Down Converter Efficiency Test ................................................................................................................... 7
More Information.................................................................................................................................................. 8
Important Notice for Richtek Evaluation Board ..................................................................................................... 8
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
your power partner.
RT2805AGSP
Evaluation Board
Introduction
General Product Description
The RT2805A is a current mode asynchronous step-down converter that achieves excellent load and line regulation.
Over a wide input voltage range from 5.5V to 36V and supports output current up to 5A. The Current mode operation
provides fast transient response and eases loop stabilization. An adjustable soft-start reduces the stress on the input
source at start up. In shutdown mode, the regulator draws only 25μA of supply current. The RT2805A requires a
minimum number of readily available external components, providing a compact solution. The RT2805A provides
protection functions inducing input under voltage lockout, cycle-by-cycle current limit, short circuit protection and
thermal shutdown protection. The RT2805A is available in the SOP-8 (Exposed Pad) package.
Product Features
5A Output Current
Wide Operating Input Range 5.5V to 36V
Adjustable Output Voltage from 1.222V to 26V
High Efficiency up to 90%
Internal Compensation Minimizes External Parts Count
Internal Soft-Start
110mΩ Internal Power MOSFET Switch
25μA Shutdown Mode
Fixed 500kHz Frequency
Thermal Shutdown
Cycle-by-Cycle Current Limit
Available In an SOP-8 (Exposed Pad) Package
RoHS Compliant and Halogen Free
Application
Distributive Power Systems
Battery Charger
DSL Modems
Pre-regulator for Linear Regulators
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
RT2805AGSP
Evaluation Board
your power partner.
Bench Test Setup Conditions
Headers Description and Placement
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
VIN
Signal
Input voltage
VOUT
SW
Output voltage
Comment (expected waveforms or voltage levels on test points)
Input voltage range = 5.5V to 36V
Output voltage = 2.4V
Switch Node
EN
Chip Enable Operation
GND
Ground
The EN pin is externally pulled to High by adding a 100kΩ resistor
(R4) from the VIN pin in this EVB setting. For another enable
operation, the converter is turned on when the EN pin is higher
than 1.4V and turned off when the EN pin is lower than 0.4V.
Ground
Power-up & Measurement Procedure
1.
Connect input power (5.5V < VIN < 36V) and input ground to VIN and GND pins respectively.
2.
Connect positive end and negative end of load to VOUT and GND of output pins respectively.
3.
The output voltage of (VOUT) can be set by R1 and R2.
VOUT = VREF * (1 + R1 / R2)
where VREF = 1.222V (typ.)
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
RT2805AGSP
Evaluation Board
your power partner.
Specification
Parameter
Symbol
Min
VIN
5.5
Input Voltage Range
Output Voltage
VOUT
Oscillator Frequency
fOSC
Output Current
IOUT
Current Limit
ILIM
Typ.
Max
Units
36
V
2.4
400
V
500
6
600
kHz
5
A
9
A
7.5
Schematic
GP1
SW
1
1
GP3
EN
D2
NC
1
2
U1
C11
Vin/5.5 to 36V
PH-8
GND
GND
SIP-2P-PW
C5
22uF
C6
0.1uF
C4
22uF
D1
B550C
100k
R5
NC
NC
ENA-5 VSENSE-4
PowerPad(Exposed Pad)
Connect to Pin6
100k
GND-6
R1
NC-3
C8
Vout/5A J2
VOUT
7uH
100nF
NC-2
R4
0.1uF
L1
BS-1
C3
C1
SIP-2P-PW
C2
4.7uF
GND
4.7uF
100k
VIN-7
C12
82pF
J1
1
R2
GP4
GND
BOM
Reference
Q'ty
P/N
Description
Package
Manufacture
U1
1
RT2805AGSP
Step-down converter
SOP-8
RICHTEK
C1, C2
2
GRM32ER71H475K
4.7μF/50V/X7R
C-1210
MURATA
C3, C6, C11
3
C1608X7R1H104K080AA
0.1μF/±10%/50V/X7R
C-0603
TDK
C4, C5
2
GRM32ER61C226KE20
22μF/±10%/16V/X5R
C-1210
MURATA
C12
1
82pF
C-0603
L1
1
74437368068
6.8μH, 6A, ±20%,
DCR = 23.3mΩ
10 x 10 x 3.8mm
D1
1
B550C
50V/5A
R1, R2, R4
3
100k
C8, R5
2
NC
EVB_RT2805AGSP-00
June 2015
WE-LHMI
DIODES
R-0402
http://www.richtek.com
RT2805AGSP
Evaluation Board
your power partner.
PCB Layout
PCB Layout (1st layer)
PCB Layout (2nd layer)
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
RT2805AGSP
Evaluation Board
your power partner.
PCB Layout (3rd layer)
PCB Layout (4th layer)
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
your power partner.
RT2805AGSP
Evaluation Board
Step-Down Converter Efficiency Test
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
your power partner.
RT2805AGSP
Evaluation Board
More Information
For more information, please find the related datasheet or application notes from Richtek website
http://www.richtek.com.
Important Notice for Richtek Evaluation Board
THIS DOCUMENT IS FOR REFERENCE ONLY, NOTHING CONTAINED IN THIS DOCUMENT SHALL BE CONSTRUED AS RICHTEK’S WARRANTY, EXPRESS
OR IMPLIED, UNDER CONTRACT, TORT OR STATUTORY, WITH RESPECT TO THE PRESENTATION HEREIN. IN NO EVENT SHALL RICHTEK BE LIABLE T O
BUYER OR USER FOR ANY AND ALL DAMAGES INCLUDING WITHOUT LIMITATION TO DIRECT, INDIRECT, SPECIAL, PUNITIVE OR CONSEQUENTIAL
DAMAGES.
EVB_RT2805AGSP-00
June 2015
http://www.richtek.com
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