®
RT2858B
3A, 18V, 650kHz ACOT
TM
Synchronous Step-Down Converter
General Description
The RT2858B is a synchronous DC/DC step-down
converter with Advanced Constant On-Time (ACOT
TM
)
mode control. It achieves high power density to deliver up
to 3A output current from a 4.5V to 18V input supply. The
proprietary ACOT
TM
mode offers an optimal transient
response over a wide range of loads and all kinds of ceramic
capacitors, which allows the device to adopt very low ESR
output capacitors for ensuring performance stabilization.
In addition, the RT2858B keeps an excellent constant
switching frequency under line and load variation and the
integrated synchronous power switches with the ACOT
TM
mode operation provides high efficiency in whole output
current load range. Cycle-by-cycle current limit provides
an accurate protection by a valley detection of low-side
MOSFET and external soft-start setting eliminates input
current surge during startup. Protection functions also
include output under voltage protection and thermal
shutdown.
Features
ACOT
TM
Control for Fast Transient, f
SW
Stability, and
Robust Loop Stability with all-MLCC C
OUT
4.5V to 18V Input Voltage Range
3A Output Current
R
DSON
120mΩ/
Ω/50mΩ
for High Efficiency Across I
OUT
Ω/
Ω
Range and Competitive Advantage for I
OUT
> 1.5A
Advanced Constant On-Time Control
Support All Ceramic Capacitors
Up to 95% Efficiency
650kHz f
SW
; Start-Up into Pre-Biased Load;
Adjustable Soft-Start; Internal Bootstrap
Adjustable Output Voltage from 0.765V to 8V
Enable; UVLO; OCP (Cycle-by-Cycle); and OTP
(150°C)
°
RoHS Compliant and Halogen Free
Applications
Industrial and Commercial Low Power Systems
Computer Peripherals
LCD Monitors and TVs
Green Electronics/Appliances
Point of Load Regulation for High-Performance DSPs,
FPGAs, and ASICs
Simplified Application Circuit
Load Transient Response
V
IN
C1
C2
RT2858B
VIN
SW
BOOT
L1
C6
C7
C3
R1
V
OUT
V
OUT
(50mV/Div)
Enable
C5
EN
SS
FB
PVCC
GND
C4
V
PVCC
R2
I
OUT
(1A/Div)
V
IN
= 12V, V
OUT
= 1.05V, I
OUT
= 0A to 3A
Time (100μs/Div)
Copyright
©
2013 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS2858B-00
September 2013
www.richtek.com
1
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
