REV. A
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a
ADP3154
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 1999
5-Bit Programmable Dual Power Supply
Controller for Pentium
®
III Processors
FUNCTIONAL BLOCK DIAGRAM
CMPI
V
T1
V
REF
+5% V
REF
–5%
DELAY
V
REF
+15%
PWRGD
SENSE+
CROWBAR
OFF
IN
NONOVERLAP
DRIVE
Q
S
R
DRIVE1 DRIVE2 PGND
2R
SENSE–
V
REF
V
CC
SD
VLDO
V
T2
CMPT
C
T
g
m
R
REFERENCE
DAC
OFF-TIME
CONTROL
V
IN
SENSE–
1.20V
CMP
FB
VID0
VID2
VID3
VID4
ADP3154
AGND
VID1
FEATURES
Active Voltage Positioning with Gain and Offset
Adjustment
Optimal Compensation for Superior Load Transient
Response
VRM 8.2, VRM 8.3 and VRM 8.4 Compliant
5-Bit Digitally Programmable 1.3 V to 3.5 V Output
Dual N-Channel Synchronous Driver
Onboard Linear Regulator Controller
Total Output Accuracy ⴞ1% Over Temperature
High Efficiency, Current-Mode Operation
Short Circuit Protection
Overvoltage Protection Crowbar Protects
Microprocessors with No Additional External
Components
Power Good Output
TSSOP-20 Package
APPLICATIONS
Desktop PC Power Supplies for:
Pentium II and Pentium III Processor Families
AMD-K6 Processors
VRM Modules
GENERAL DESCRIPTION
The ADP3154 is a highly efficient synchronous buck switching
regulator controller optimized for converting the 5 V main sup-
ply into the core supply voltage required by the Pentium III and
other high performance processors. The ADP3154 uses an
internal 5-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 3.5 V. The ADP3154 uses a current
mode, constant off-time architecture to drive two external N-
channel MOSFETs at a programmable switching frequency that
can be optimized for size and efficiency. It also uses a unique
supplemental regulation technique called active voltage position-
ing to enhance load transient performance.
Active voltage positioning results in a dc/dc converter that meets
the stringent output voltage specifications for Pentium II and
Pentium III 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
that it is always optimally positioned for a system transient.
The ADP3154 provides accurate and reliable short circuit pro-
tection and adjustable current limiting. It also includes an
integrated overvoltage crowbar function to protect the micro-
processor from destruction in case the core supply exceeds the
nominal programmed voltage by more than 15%.
The ADP3154 contains a linear regulator controller that is
designed to drive an external N-channel MOSFET. This linear
regulator is used to generate the auxiliary voltages (AGP, GTL,
etc.) required in most motherboard designs, and has been de-
signed to provide a high bandwidth load-transient response. A
pair of external feedback resistors sets the linear regulator out-
put voltage.
V
CC
+12V
1mF
22mF
V
IN
+5V
+
C
IN
L
+
C
O
V
O
1.3V TO
3.5V
R
SENSE
1nF
C
COMP
35kV
20kV
V
O2
1000mF
R1
200pF
V
CC
SD
DRIVE1
SENSE+
SENSE–
DRIVE2
PGNDAGND
C
T
CMP
ADP3154
FB
VLDO
R2
VID0–VID4
5-BIT CODE
Figure 1. Typical Application
Pentium is a registered trademark of Intel Corporation.
All other trademarks are the property of their respective holders.
