DS6203B Datasheet, PDF (3/22 Pages) Richtek Technology Corporation – 5A, 18V, 700kHz ACOTTM Synchronous Step-Down Converter with VID Control

Functional Block Diagram
VCC PVCC
RT6203B
BOOT
AGND
SS
FB
VS
SDA
SCL
A0
A1
Reg
VIBIAS
VREG5
6µA
PVCC
V_REF
OC
UV & OV
EXT
Min.
Off
Control
DAC OUT
INT
EXT
+
+
-
Comparator
PVCC
Driver
ZC SW
UGATE
LGATE
Comparator
+
INT
VIN
On-Time
DAC OUT
VREF
EXT
INT
-
92.5%
Serial
Interface
DAC
7bits
Chip
Address
V_OUT = 0.72V
to 1.48V
DAC OUT
01101A1A0
EN
VIN
SW
PGND
PGOOD
Operation
The RT6203B is a high-performance 700kHz 5A step-down
regulator with internal power switches and synchronous
rectifiers. It features an Advanced Constant On-Time
(ACOT^TM) control architecture that provides stable
operation with ceramic output capacitors without
complicated external compensation, among other benefits.
The ACOT^TM control mode also provides fast transient
response, especially for low output voltages and low duty
cycles. The input voltage range is from 4.5V to 18V and
the output is adjustable from 0.8V to 8V. The proprietary
ACOT^TM control scheme improves upon other constant
on-time architectures, achieving nearly constant switching
frequency over line, load, and output voltage ranges. The
RT6203B are optimized for ceramic output capacitors.
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.
Copyright ©2016 Richtek Technology Corporation. All rights reserved.
DS6203B-00 September 2016
EN
Constant On-Time (COT) Control
The heart of any COT architecture is the on-time one shot.
Each on-time is a pre-determined “fixed” period that is
triggered by a feedback comparator. This robust
arrangement has high noise immunity and is ideal for low
duty cycle applications. After the on-time one-shot period,
there is a minimum off-time period before any further
regulation decisions can be considered. This arrangement
avoids the need to make any decisions during the noisy
time periods just after switching events, when the
switching node (SW) rises or falls. Because there is no
fixed clock, the high-side switch can turn on almost
immediately after load transients and further switching
pulses can ramp the inductor current higher to meet load
requirements with minimal delays. Traditional current
mode or voltage mode control schemes typically must
monitor the feedback voltage, current signals (also for
current limit), and internal ramps and compensation
signals, to determine when to turn off the high-side switch
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