REV.A
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a
ADP3158/ADP3178
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 2001
4-Bit Programmable
Synchronous Buck Controllers
FUNCTIONAL BLOCK DIAGRAM
g
m
CMP
+–
DRVH
LRDRV2
LRFB2
LRFB1
LRDRV1
COMP
DRVL
GND
CS–
CS+
PWM
DRIVE
VCC CT
OSCILLATOR
UVLO
& BIAS
REFERENCE REF
V
LR1
V
LR2
REF VID DAC
DAC+20%
ADP3158/ADP3178
VID3 VID2 VID1 VID0
FEATURES
Optimally Compensated Active Voltage Positioning
with Gain and Offset Adjustment (ADOPT™) for
Superior Load Transient Response
Complies with VRM Specifications with Lowest
System Cost
4-Bit Digitally Programmable 1.3 V to 2.05 V Output
N-Channel Synchronous Buck Driver
Total Accuracy H115500.8% Over Temperature
Two On-Board Linear Regulator Controllers Designed
to Meet System Power Sequencing Requirements
High Efficiency Current-Mode Operation
Short Circuit Protection for Switching Regulator
Overvoltage Protection Crowbar Protects Micro-
processors with No Additional External Components
APPLICATIONS
Core Supply Voltage Generation for:
Intel Pentium
®
III
Intel Celeron™
GENERAL DESCRIPTION
The ADP3158 and ADP3178 are highly efficient synchronous
buck switching regulator controllers optimized for converting a
5 V main supply into the core supply voltage required by high-
performance processors. These devices use an internal 4-bit DAC
to read a voltage identification (VID) code directly from the
processor, which is used to set the output voltage between 1.3 V
and 2.05 V. They use a current mode, constant off-time archi-
tecture to drive two N-channel MOSFETs at a programmable
switching frequency that can be optimized for regulator size and
efficiency.
The ADP3158 and ADP3178 also use a unique supplemental
regulation technique called Analog Devices Optimal Positioning
Technology (ADOPT) to enhance load transient performance.
Active voltage positioning results in a dc/dc converter that
meets the stringent output voltage specifications for high-
performance processors, with the minimum number of output
capacitors and smallest footprint. Unlike voltage-mode and
standard current-mode architectures, active voltage positioning
adjusts the output voltage as a function of the load current so it
is always optimally positioned for a system transient. They also
provide accurate and reliable short circuit protection and
adjustable current limiting. The devices include an integrated
overvoltage crowbar function to protect the microprocessor
from destruction in case the core supply exceeds the nominal
programmed voltage by more than 20%.
The ADP3158 and ADP3178 contain two linear regulator
controllers that are designed to drive external N-channel
MOSFETs. The outputs are internally fixed at 2.5 V and 1.8 V
in the ADP3158, while the ADP3178 provides adjustable out-
puts that are set using an external resistor divider. These
linear regulators are used to generate the auxiliary voltages
(AGP, GTL, etc.) required in most motherboard designs,
and have been designed to provide a high bandwidth load-
transient response.
The ADP3158 and ADP3178 are specified over the commercial
temperature range of 0°C to 70°C and are available in a 16-lead
SOIC package.
ADOPT is a trademark of Analog Devices, Inc.
Pentium is a registered trademark of Intel Corporation.
Celeron is a trademark of Intel Corporation.