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.

SC2642. The MOSFET R

winding resistance are used to generate the phase cur-

the SC2642 enables the complete solution.

The SC2642 is a multi-platform controller. It conforms to

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%

!

!

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

!

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.