2, 3 or 4 Phase
Combi-Sense
TM
PWM Controller
POWER MANAGEMENT
Description
The SC2646B controller provides a microprocessor core
voltage regulation solution for up to 4 paralleled PWM
channels. The solution can be configured in 2, 3, or 4-
phase form. This multi-phase buck regulator utilizes
phase-shift timing control to allow interleaved switching
of the power switches. The product鈥檚 architecture mini-
mizes the core voltage ripple and the input current ripple,
which leads to optimized voltage regulator design for
power density, transient responses, and thermal
performances.
To satisfy the highly dynamic nature of the modern micro-
processors, the SC2646B adopts peak current mode
control topology which ensures wide control loop band-
width and fast transient responses. The current mode
control provides intrinsic phase current matching. The
maximum ripple frequency is greater than 2MHz.
One of the outstanding features of the SC2646B device
is its voltage regulation accuracy. Not only does it pro-
vide 0.5% set point accuracy, but also the accuracy to
be fully compliant with stringent load line slope specifi-
cations mandated by the modern microprocessors.
Lossless output current sensing ensures the regulator
output voltage is accurately positioned according to the
load current condition.
Semtech鈥檚 patented Combi-Sense
TM
topology is employed
by SC2646B controller. The MOSFET R
ds(on)
and the out-
put inductor winding resistance is used to generate the
phase current information. Semtech鈥檚 SC1211 Combi-
Sense
TM
MOSFET driver works with the SC2646B to en-
able a complete solution.
The cycle-by-cycle current limit plus the intelligent over
current shut down provide the maximum versatility of
the system without false tripping under all possible
changes of VID and load conditions. The differential
voltage feedback sense eliminates the error caused by
high load current on the ground plane. External offset is
easy to achieve for the VID settings. The enable func-
tion is also provided to interface with the corresponding
system signal for correct start up timing and shut down
timing.
SC2646B
Features
VRD/VRM10.X compliant
Core Voltage Set Point Accuracy 0.5%
Combi-Sense
TM
Current Mode Control
Intrinsic Phase Current Matching
Fast Transient Responses
Active Droop to Meet Load Line Slope
Enable Function for Power Sequencing
Cycle-by-Cycle Peak Current Limit
Intelligent Over Current Shut Down
Over Voltage Protection When Using Semtech
Combi-Sense
TM
Driver SC1211
Under Voltage Protection Built in
Externally Programmable Soft-Start
Externally Programmable Switching Frequency
2, 3, or 4-Phase Configurations
24-Pin TSSOP Package
Combi-Sense
TM
is a Trademark of Semtech Corporation
Applications
Voltage Regulator VRD/VRM10.X
Voltage Regulation Modules
High Current, Low Voltage Step Down DC/DC
Converters
Revision: Apr. 11, 2005
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