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ADP3153ARU Schematic ( PDF Datasheet ) - Analog Devices

Teilenummer ADP3153ARU
Beschreibung 5-Bit Programmable Dual Power Supply Controller for Pentium II Processor
Hersteller Analog Devices
Logo Analog Devices Logo 




Gesamt 12 Seiten
ADP3153ARU Datasheet, Funktion
a
FEATURES
5-Bit Digitally Programmable 1.8 V to 3.5 V Output
Voltage
Dual N-Channel Synchronous Driver
Total Output Accuracy ؎1% (0؇C to +70؇C)
High Efficiency
Current-Mode Operation
Short Circuit Protection
Power Good Output
Overvoltage Protection Crowbar
On-Board Linear Regulator Controller
VRM 8.2 Compatible
Narrow Body TSSOP 20-Lead Package
APPLICATIONS
Desktop PC Power Supply for:
Pentium II Processor
Deschutes Processor
Pentium Pro Processor
Pentium Processor
AMD–K6 Processor
VRM Modules
5-Bit Programmable Dual
Power Supply Controller
for Pentium® II Processor
ADP3153
GENERAL DESCRIPTION
The ADP3153 is a highly efficient synchronous switching regu-
lator controller and a linear regulator controller. The switching
regulator controller is optimized for Pentium II and Deschutes
Processor applications where 5 V is stepped down to a digitally
controlled output voltage between 1.8 V and 3.5 V. Using a 5-bit
DAC to read a voltage identification (VID) code directly from
the processor, the ADP3153 uses a current mode constant off-
time architecture to generate its precise output voltage.
The ADP3153 drives two N-channel MOSFETS in a synchro-
nous rectified buck converter, at a maximum switching fre-
quency of 250 kHz. Using the recommended loop compensation
and guidelines, the ADP3153 provides a dc/dc converter that
meets Intel’s stringent transient specifications with a minimum
number of output capacitors and smallest footprint. Addition-
ally, the current mode architecture also provides guaranteed
short circuit protection and adjustable current limiting.
The ADP3153’s linear regulator controller drives an external
N-channel device. The output voltage is set by the ratio of the
external feedback resistors. The controller has been designed for
excellent load transient response.
VCC
+12V
VIN
+5V
VO2
+3.3V
1A
R1
VIN
+5V R2
IRL2703
1000F
35k
20k
22F 1F
CCOMP
SD VCC
DRIVE1
CMP
ADP3153
VLDO
SENSE+
SENSE–
IRL3103
1nF
150pF
FB DRIVE2
CT PGND
AGND
VID0–VID4
IRL3103
+ CIN
L
2.5H
RSENSE
7m
10BQ015
+ CO
VO
1.8V–3.5V
14A
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.
REV. 0
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.
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., 1998






ADP3153ARU Datasheet, Funktion
ADP3153
12V Table I. Output Voltage vs. VID Code
5-BIT
VID0–
VCC
CODE
VID4
ADP3153
SD DRIVE1
1k
4700pF
CMP
CT
AGND
DRIVE2
SENSE+
SENSE–
PGND
1F 0.1F
VOUT
1.2V
100k
OP27
0.1F
Figure 13. Closed-Loop Test Circuit for Accuracy
APPLICATION INFORMATION
The ADP3153 uses a current-mode, constant-off-time control
technique to switch a pair of external N-channel MOSFETs in
a synchronous rectified buck converter application. Due to the
constant-off-time operation, no slope compensation is needed.
A unique feature of the constant-off-time control technique is
that the converter’s frequency becomes a function of the ratio of
input voltage to output voltage. The off time is determined by
the value of the external capacitor connected to the CT pin.
The on time varies in such a way that a regulated output volt-
age is maintained.
The output voltage is sensed by an internal voltage divider that
is connected to the SENSE– pin. A voltage-error amplifier gm
compares the values of the divided output voltage with a refer-
ence voltage. The reference voltage is set by an on-board 5-bit
DAC, which reads the code present at the voltage identification
(VID) pins and converts it to a precise value between 600 mV
and 1.167 V. Refer to Table I for the output voltage vs. VID pin
code information.
During continuous-inductor-current mode of operation, the
voltage-error amplifier gm and the current comparator CMPI
are the main control elements. During the on time of the high
side MOSFET, the current comparator CMPI monitors the
voltage between the SENSE+ and SENSE– pins. When the
voltage level between the two pins reaches the threshold level
VT1, the high side drive output is switched to zero, which turns
off the high side MOSFET. The timing capacitor CT is now
discharged at a rate determined by the off time controller. In
order to maintain a ripple current in the inductor, which is
independent of the output voltage, the discharge current is
made proportional to the value of the output voltage (mea-
sured at the SENSE– pin). While the timing capacitor is dis-
charging, the low side drive output goes high, turning on the
low side MOSFET. When the voltage level on the timing ca-
pacitor has discharged to the threshold voltage level VT2,
comparator CMPT resets the SR flip-flop. The output of the
flip-flop forces the low side drive output to go low and the high
side drive output to go high. As a result, the low side switch is
turned off and the high side switch is turned on. The sequence is
then repeated. As the load current increases, the output voltage
starts to decrease. This causes an increase in the output of the
voltage-error amplifier, which, in turn, leads to an increase in
the current comparator threshold VT1, thus tracking the load
current.
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
VID3
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
VID2
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
VID1
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
VID0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
VOUT
1.80
1.80
1.80
1.80
1.80
1.80
1.80
1.80
1.80
1.80
1.80
1.85
1.90
1.95
2.00
2.05
Shutdown
2.10
2.20
2.30
2.40
2.50
2.60
2.70
2.80
2.90
3.00
3.10
3.20
3.30
3.40
3.50
To prevent cross conduction of the external MOSFETs, feed-
back is incorporated to sense the state of the driver output pins.
Before the low side drive output can go high, the high side drive
output must be low. Likewise, the high side drive output is
unable to go high while the low side drive output is high.
Power Good
The ADP3153 has an internal monitor which monitors 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 the output voltage has been
within a ± 5% regulation band of the targeted value for more
than 500 µs. The PWRGD pin will go low if the output is out-
side the regulation band for more than 500 µs.
Output Crowbar
An added feature of using an N-channel MOSFET as the syn-
chronous switch is the ability to crowbar the output with the
same MOSFET. If the output voltage is 15% greater than the
desired regulated value, the ADP3153 will turn on the lower
MOSFET, which will current-limit the source power supply or
blow its fuse, pull down the output voltage, and thus save the
expensive microprocessor from destruction. The crowbar func-
tion releases at approximately 50% of the nominal output volt-
age. For example, if the output is programmed to 2.0 V, but is
pulled up to 2.3 V or above, the crowbar will turn on the lower
MOSFET. If in this case the output is pulled down to less than
–6– REV. 0

6 Page









ADP3153ARU pdf, datenblatt
ADP3153
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)
20
0.177 (4.50)
0.169 (4.30)
1
11
0.256 (6.50)
0.246 (6.25)
10
0.006 (0.15) PIN 1
0.002 (0.05)
0.0433 (1.10)
MAX
0.0256 (0.65)
SEATING
PLANE
BSC
8؇
0.0118 (0.30)
0.0075 (0.19)
0.0079 (0.20) 0؇
0.0035 (0.090)
0.028 (0.70)
0.020 (0.50)
–12–
REV. 0

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