5-Bit Programmable Dual Power Supply
®
a
Controller for Pentium III Processors
ADP3154
FEATURES
FUNCTIONAL BLOCK DIAGRAM
Active Voltage Positioning with Gain and Offset
Adjustment
AGND
V
DRIVE1 DRIVE2 PGND
SENSE+ SENSE–
PWRGD
CC
Optimal Compensation for Superior Load Transient
Response
DELAY
+15%
NONOVERLAP
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 ؎1% Over Temperature
High Efficiency, Current-Mode Operation
Short Circuit Protection
Overvoltage Protection Crowbar Protects
Microprocessors with No Additional External
Components
V
DRIVE
REF
SD
2R
CROWBAR
OFF
IN
V
+5% V
–5%
REF
REF
CMPI
V
T1
S
Q
R
R
V
REF
g
m
V
T2
REFERENCE
Power Good Output
TSSOP-20 Package
VLDO
FB
C
T
CMPT
1.20V
V
APPLICATIONS
OFF-TIME
CONTROL
IN
VID0
VID1
VID2
VID3
VID4
SENSE–
Desktop PC Power Supplies for:
Pentium II and Pentium III Processor Families
AMD-K6 Processors
VRM Modules
ADP3154
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.
DAC
CMP
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
+12V
CC
V
+5V
IN
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.
C
+
IN
22F
1F
R1
V
CC
SD
DRIVE1
VLDO
L
V
RSENSE
O
V
1.3V TO
O2
ADP3154
3.5V
35k⍀
+
SENSE+
1000F
FB
C
O
1nF
20k⍀
CMP
SENSE–
DRIVE2
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%.
R2
CCOMP
C
T
200pF
AGND PGND
VID0–VID4
5-BIT CODE
Pentium is a registered trademark of Intel Corporation.
All other trademarks are the property of their respective holders.
Figure 1. Typical Application
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, nor for any infringements of patents or other rights of third parties
which 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
Fax: 781/326-8703
World Wide Web Site: http://www.analog.com
© Analog Devices, Inc., 1999