ADP3155JRU Analog Devices, ADP3155JRU Datasheet

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ADP3155JRU

Manufacturer Part Number
ADP3155JRU
Description
Manufacturer
Analog Devices
Datasheet

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a
Pentium is a registered trademark of Intel Corporation.
All other trademarks are the property of their respective holders.
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.
GENERAL DESCRIPTION
The ADP3155 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 ADP3155 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 ADP3155 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 the 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 ADP3155 provides accurate and reliable short circuit pro-
tection and adjustable current limiting. It also includes an inte-
grated overvoltage crowbar function to protect the microprocessor
from destruction in case the core supply exceeds the nominal
programmed voltage by more than 15%.
REV. A
FEATURES
Active Voltage Positioning with Gain and Offset
Optimal Compensation for Superior Load Transient
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
Two Onboard Linear Regulator Controllers
Total Output Accuracy
High Efficiency, Current-Mode Operation
Short Circuit Protection
Overvoltage Protection Crowbar Protects Micro-
Power Good Output
TSSOP-20 Package
APPLICATIONS
Desktop PC Power Supplies for:
Adjustment
Response
processors, with No Additional External Components
Pentium II and Pentium III Processor Families
AMD-K6 Processors
VRM Modules
1% Over Temperature
5-Bit Programmable Triple Power Supply
Controller for Pentium
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700
Fax: 781/326-8703
The ADP3155 contains two linear regulator controllers that are
designed to drive external N-channel MOSFETs. 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 re-
sponse. A pair of external feedback resistors sets each linear
regulator output voltage.
CMP
V
R2
R1
SD
C
OLDO2
T
V
OLDO1
1 F
V
Q
CC
LDO2
C
V
V
1 F
DRIVE1 DRIVE2 PGND
22 F
COMP
Q
T2
INLDO2
NONOVERLAP
IN
ADP3155
S
R
OFF-TIME
CONTROL
Q
R5
R6
20k
CROWBAR
FUNCTIONAL BLOCK DIAGRAM
DRIVE
CMPT
LDO1
OFF
V
Figure 1. Typical Application
INLDO1
1 F
R4
20k
R3
World Wide Web Site: http://www.analog.com
V
SENSE–
CMPI
IN
SD
CMP
V
FB1
V
FB2
CMP
LDO1
LDO2
ADP3155
5-BIT CODE
VID0–VID4
V
VID4
DAC
+15%
CC
V
V
AGND
REF
SENSE+
SENSE–
CC
+12V
DRIVE1
DRIVE2
PGND
AGND
VID3
®
V
V
+5%
T1
REF
C
g
PWRGD
T
m
VID2
III Processors
150pF
V
V
IN
–5%
© Analog Devices, Inc., 1999
V
REF
DELAY
+5V
REF
VID1
Q1
Q2
+
C
ADP3155
SENSE+
IN
VID0
REFERENCE
L
1nF
R
1.20V
SENSE
SENSE–
R
2R
+
C
O
V
1.3V TO
3.5V
O
VLDO2
FB2
VLDO1
FB1

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ADP3155JRU Summary of contents

Page 1

... Pentium is a registered trademark of Intel Corporation. All other trademarks are the property of their respective holders. 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 ...

Page 2

ADP3155–SPECIFICATIONS Parameter OUTPUT ACCURACY 1.3 V Output Voltage 2.0 V Output Voltage 3.5 V Output Voltage OUTPUT VOLTAGE LINE REGULATION 2 INPUT DC SUPPLY CURRENT Normal Mode Shutdown CURRENT SENSE THRESHOLD VOLTAGE VID0–VID4 THRESHOLD Low High VID0–VID4 INPUT CURRENT VID0–VID4 ...

Page 3

... ORDERING GUIDE Temperature Package Model Range Description ADP3155JRU +70 C Thin Shrink Small RU-20 Outline (TSSOP) CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the ADP3155 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges ...

Page 4

ADP3155 P 1 SYSTEM IRF3103 8 470pF LDO1 +1. 1000 F 5k RTN R3 20k Figure 2. Typical VRM8.2/8.3/8.4 Compliant Core DC/DC Converter Circuit V DRIVE1 ...

Page 5

V = 3.5V OUT V = 2.8V 95 OUT 2.0V OUT V = 1.3V OUT SEE FIGURE 2 65 1.4 2.8 4.2 5.6 7 8.4 9.8 11.2 12.6 14 OUTPUT CURRENT – ...

Page 6

ADP3155 VID0– V 5-BIT CODE CC VID4 ADP3155 SD DRIVE1 CMP DRIVE2 1k C SENSE+ T SENSE– 4700pF AGND PGND OP27 100k 1.2V 0.1 F Figure 13. Closed-Loop Test Circuit for Accuracy THEORY OF OPERATION The ADP3155 uses a current-mode, ...

Page 7

Power Good The ADP3155 has an internal monitor that senses the output voltage and drives the PWRGD pin of the device. This pin is an open drain output whose high level (when connected to a pull- up resistor) indicates that ...

Page 8

ADP3155 Transient tolerance (for less than the supply voltage for the processor core when the load changes between the mini- mum and maximum values with a di/ 130 mV OTR+ V ...

Page 9

Tips for Selecting the Inductor Core Ferrite designs have very low core loss, so the design should focus on copper loss and on preventing saturation. Molypermalloy, or MPP low loss core material for toroids, and it yields the ...

Page 10

ADP3155 high side FET, however, is turned on with only 12 V – Checking the typical output characteristics of the device in the data sheet shows that for an output current and ...

Page 11

V supply of the IC. The values of these resistors can ...

Page 12

ADP3155 Linear Regulator Design Example Maximum Ambient Temperature . . . . . . . . . . . . T Input Voltage . . . . . . . . . . . . . . . . . ...

Page 13

The output capacitors should also be connected as closely as possible to the load (or connector) that receives the power (e.g., a microprocessor core). If the load is distrib- uted, the capacitors also should be distributed, and gen- erally ...

Page 14

ADP3155 0.177 (4.50) 0.169 (4.30) 0.006 (0.15) 0.002 (0.05) SEATING OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 20-Lead Thin Shrink Small Outline (TSSOP) RU-20 0.260 (6.60) 0.252 (6.40 0.256 (6.50) 0.246 (6.25 PIN 1 0.0433 ...

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