4-Bit Programmable
Synchronous Buck Controllers
a
ADP3158/ADP3178
FEATURES
FUNCTIO NAL BLO CK D IAGRAM
Optimally Compensated Active Voltage Positioning
with Gain and Offset Adjustment (ADOPT™) for
Superior Load Transient Response
Complies with VRM Specifications with Lowest
System Cost
VCC
CT
ADP3158/ADP3178
UVLO
& BIAS
DRVH
OSCILLATOR
PWM
DRIVE
4-Bit Digitally Programmable 1.3 V to 2.05 V Output
N-Channel Synchronous Buck Driver
DRVL
GND
Total Accuracy ꢀ0.8% 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
REF
REFERENCE
DAC+20%
V
LR1
CS–
CS+
LRFB1
CMP
– +
LRDRV1
V
LR2
APPLICATIONS
LRFB2
Core Supply Voltage Generation for:
g
m
Intel Pentium® III
LRDRV2
COMP
Intel Celeron™
REF
VID DAC
VID3
VID2
VID1
VID0
GENERAL D ESCRIP TIO N
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. T hey also
provide accurate and reliable short circuit protection and
adjustable current limiting. T he 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%.
T he 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. T hey 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.
T he AD P3158 and AD P3178 contain two linear regulator
controllers that are designed to drive external N -channel
M OSFET s. T he 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. T hese
linear regulators are used to generate the auxiliary voltages
(AGP, GT L, etc.) required in most motherboard designs,
and have been designed to provide a high bandwidth load-
transient response.
T he ADP3158 and ADP3178 also use a unique supplemental
regulation technique called Analog Devices Optimal Positioning
T echnology (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
T he 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.
REV. A
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, norforanyinfringementsofpatentsorotherrightsofthirdpartiesthat
may result from its use. No license is granted by implication or otherwise
under any patent or patent rights of Analog Devices.
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Tel: 781/329-4700
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© Analog Devices, Inc., 2001