POWER MANAGEMENT
Description
The SC2643VX provides a solution for microprocessor core
voltage regulation with up to 4 paralleled PWM channels.
The solution can also be configured as 2, 3, or 4-phase
form. This multi-phase buck regulator utilizes the phase-
shift timing control to allow interleaved switching of the
power switches. This architecture minimizes the core volt-
age ripple and the input current ripple, which leads to op-
timized voltage regulator design for power density, tran-
sient responses, and the thermal performances.
To satisfy the highly dynamic nature of the modern micro-
processors, the SC2643VX adopts peak current mode con-
trol topology which ensures wide control loop bandwidth
and fast transient responses. The current mode control
provides intrinsic phase current matching. The maximum
ripple frequency is greater than 2.8MHz.
One of the outstanding features of the SC2643VX is its
voltage regulation accuracy. Not only does it provide bet-
ter than 0.5% set point accuracy, but also the accuracy to
be fully compliant with stringent load line slope specifica-
tions mandated by the modern microprocessors. Lossless
output current sensing ensures the regulator output volt-
age is accurately positioned according to the load current
condition, and an internal temperature compensation tech-
nology further enhances the performance of voltage accu-
racy.
The patented Combi-Sense
TM
topology is employed by
SC2643VX. The MOSFET R
ds(on)
and the output inductor
winding resistance are used to generate the phase current
information. The Combi-Sense
TM
MOSFET driver plus the
SC2643VX enables the complete solution.
The SC2643VX is a multi-platform controller. It conforms
to Intel VRM/VRD10.X, VRM9.X, and AMD K-8 (Opteron
TM
)
VID specifications. With very minor changes of the sche-
matic and the layout, the SC2643VX based solution can
be ported form one platform to another. This greatly ben-
efits system manufactures by reducing design cycle times
and streamlining inventory management.
The SC2643VX supports VID-on-Fly applications for any
platform. The cycle-by-cycle current limit plus the intelli-
gent over current shut down provide the maximum versa-
tility of the system without false tripping under all possible
changes of VID and load conditions. The differential volt-
age feedback sense eliminates the error caused by high
May 11, 2005
1
Multi-Platform
Multi-Phase PWM Controller
load current on the ground plane. External offset is easy
to achieve for any platforms and the VID settings. The
enable function is also provided to interface with the cor-
responding system signal for correct start up timing and
shut down timing.
(Multiple Patents Pending)
SC2643VX
Features
VRD/VRM10.X, VRM9.X, and K-8 compliant
Core Voltage Set Point Accuracy 0.5%
Combi-Sense
TM
Current Mode Control
Intrinsic Phase Current Matching
Fast Transient Responses
Active Droop with Temperature Compensation to
Meet Load Line Slope
Support VID-on-Fly with 5 or 6 bit VID
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
Under Voltage Protection Built in
External programmable Soft-Start
Externally programmable switching frequency (up to
2.8MHz output voltage ripple frequency)
2, 3, or 4-Phase Configurations
Applications
Voltage Regulator VRD/VRM10.X
Voltage Regulator VRM9.X
Voltage Regulator K-8
High Current, Low Voltage Step Down DC/DC
Converters
www.semtech.com
SEMTECH [ SEMTECH CORPORATION ]
