1
www.semtech.com
POWER MANAGEMENT
SC2642
Multi-Platform
Two-Phase PWM Controller
April 22, 2005
Description
Applications
The SC2642 provides microprocessor core voltage
regulation solution with two paralleled PWM channels.
Multi-phase buck regulator utilizes the phase-shift tim-
ing control to allow interleaved switching of the power
switches. This architecture minimizes the core voltage
ripple and the input current ripple, which leads to opti-
mized voltage regulator design for power density, tran-
sient responses, and the thermal performances.
To satisfy the highly dynamic nature of the modern
microprocessors, the SC2642 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 1MHz.
One of the outstanding features of the SC2642 is its volt-
age regulation accuracy. Not only it provides better than
1% set point accuracy, but also the accuracy to fully com-
plaint with the stringent load line slope specifications
mandated by the modern microprocessors.Lossless out-
put current sensing ensures the regulator output voltage
is accurately positioned according to the load current con-
dition, and an internal temperature compensation tech-
nology further enhances the performance of voltage ac-
curacy.
The patented Combi-Sense
TM
topology is employed by
SC2642. The MOSFET R
ds(on)
and the output inductor
winding resistance are used to generate the phase cur-
rent information. The Combi-Sense
TM
MOSFET driver plus
the SC2642 enables the complete solution.
The SC2642 is a multi-platform controller. It conforms to
Intel VRM/VRD10.0, VRM9.X, and AMD K-8 (Opteron
TM
)
VID specifications. With very minor changes of the sche-
matic and the layout, the SC2642 based solution can be
ported form one platform to another. This greatly ben-
efits the system manufactures for reductions of design
cycle and minimize the inventory management.
!
VRD/VRM10.0, 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 SC1211
!
Under Voltage Protection Built in
!
External programmable Soft-Start
!
Externally programmable switching frequency (up to
1MHz output ripple frequency)
!
Voltage Regulator VRD10.x
!
Voltage Regulator VRM9.X
!
Voltage Regulator K-8
!
High Current, Low Voltage Step Down DC/DC
Converters
Features
The VID structure of the SC2642 supports VID-on-Fly ap-
plications for any platform. 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 any platforms and
the VID settings. The enable function is also provided to
interface with the corresponding system signal for correct
start up timing and shut down timing.
3
2005 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC2642
Absolute Maximum Ratings
Electrical Characteristics
Exceeding the specifications below may result in permanent damage to the device, or device malfunction. Operation outside of the parameters specified in the Electrical
Characteristics section is not implied.
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NOTE : 1) Guaranteed by design, not tested in production. Specifications subject to change without notice.
Unless specified: V
CC
= 12V, VID=1.50V (101110,VRD10), F
OSC
= 200kHz/phase, T
A
= 27
o
C. See Typical Application Circuit.
4
2005 Semtech Corp.
www.semtech.com
POWER MANAGEMENT
SC2642
Electrical Characteristics (Cont.)
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NOTE : 1) Guaranteed by design, not tested in production. Specifications subject to change without notice.
Unless specified: V
CC
= 12V, VID=1.50V (101110,VRD10), F
OSC
= 200kHz/phase, T
A
= 27
o
C. See Typical Application Circuit.
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