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PDF ( 数据手册 , 数据表 ) ADM1052

零件编号 ADM1052
描述 Precision Dual Voltage Regulator Controller
制造商 Analog Devices
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ADM1052 数据手册, 描述, 功能
a
FEATURES
Two Independent Controllers on One Chip
Two 2.525 V Outputs
Shutdown Inputs to Control Each Channel
؎2.5% Accuracy Over Line, Load, and Temperature
Low Quiescent Current
Low Shutdown Current
Works with External N-Channel MOSFETs for Low Cost
“Hiccup Mode” Fault Protection
No External Voltage or Current Setting Resistors
Small, 8-Lead SO Package
APPLICATIONS
Desktop Computers
Servers
Workstations
Precision Dual Voltage
Regulator Controller
ADM1052
GENERAL DESCRIPTION
The ADM1052 is a dual, precision, voltage regulator controller
intended for power rail generation and active bus termination
on personal computer motherboards. It contains a precision
1.2 V bandgap reference and two channels consisting of con-
trol amplifiers driving external power devices. Each channel has a
shutdown input to turn off amplifier output and “Hiccup Mode”
protection circuitry for the external power device.
The ADM1052 operates from a 12 V supply. This gives suffi-
cient headroom for the amplifiers to drive external N-channel
MOSFETs, operating as source-followers, as the external series
pass devices. This has the advantage that N-channel devices are
cheaper than P-channel devices of similar performance, and the
circuit is easier to stabilize than one using P-channel devices in
a common-source configuration.
SHDN1
ADM1052
VCC
50A
FUNCTIONAL BLOCK DIAGRAM
VCC
BANDGAP
REFERENCE
SHUTDOWN
CONTROL
HICCUP
COMPARATOR
3.3V
CONTROL
AMPLIFIER
FORCE 1
SENSE 1
100F
VOUT1
2 ؋ 100F
3.3V
SHDN2
VCC
50A
VCC
CONTROL
AMPLIFIER
FORCE 2
SENSE 2
SHUTDOWN
CONTROL
HICCUP
COMPARATOR
100F
VOUT2
2 ؋ 100F
POWER-ON
RESET
CLK/DELAY
GENERATOR
CLOCK
OSCILLATOR
GND
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.
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., 2001







ADM1052 pdf, 数据表
ADM1052
12V
3.3V
1F
VCC
FORCE 1
100F
LEAVE OPEN OR
CONNECT TO
LOGIC SIGNALS
IF SHUTDOWN
REQUIRED
SENSE 1
SHDN1
ADM1052
SHDN2
FORCE 2
VOUT1
2 ؋ 100F
3.3V
100F
GND
SENSE 2
VOUT2
2 ؋ 100F
Figure 4. Typical Application Circuit
SUPPLY DECOUPLING
The supply to the drain of an external MOSFET should be decoupled
as close as possible to the drain pin of the device, with a 100 µF
capacitor to ground. The output from the source of the MOSFET
should be decoupled as close as possible to the source pin of the
device. Decoupling capacitors should be chosen to have a low
Equivalent Series Resistance (ESR). With the MOSFETs specified
and two 100 µF capacitors in parallel, the circuit will be stable for
load currents up to 2 A. The VCC pin of the ADM1052 should be
decoupled with a 1 µF capacitor to ground, connected as close as
possible to the VCC and GND pins.
In practice, the amount of decoupling required will depend on
the application. PC motherboards are notoriously noisy environ-
ments, and it may be necessary to employ distributed decoupling
to achieve acceptable noise levels on the supply rails.
CHOICE OF MOSFET
As previously discussed, the load current at which an output
goes into hiccup mode depends on the on-resistance of the
external MOSFET. If the on-resistance is too low this current
may be very high. While the Test Circuit (Figure 1) shows the
use of the lower resistance PHD55N03LT from Philips on
Channel 1 and the use of the higher resistance MTD3055VL
from Motorola on Channel 2, the MTD3055VL is, in fact,
suitable for both channels. Similarly, the PHB11N06LT from
Philips is also suitable for both channels.
THERMAL CONSIDERATIONS
Heat generated in the external MOSFET must be dissipated
and the junction temperature of the device kept within accept-
able limits. The power dissipated in the device is, of course, the
drain-source voltage multiplied by the load current. The required
thermal resistance to ambient is given by
JA = TJ(MAX) TAMB(MAX)/(VDS(MAX) × IOUT(MAX))
Surface-mount MOSFETs such as those specified must rely on
heat conduction through the device leads and the PCB. One
square inch of copper (645 sq. mm) gives a thermal resistance of
around 60°C/W for a SOT-223 surface-mount package and
80°C/W for a SO-8 surface-mount package.
For higher power dissipation than can be accommodated by a
surface-mount package D2PAK or TO-220 devices are recom-
mended. These should be mounted on a heatsink with a thermal
resistance low enough to maintain the required maximum junc-
tion temperature.
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
8-Lead Small Outline Package
(Narrow Body, SO-8)
0.1968 (5.00)
0.1890 (4.80)
8
0.1574 (4.00)
0.1497 (3.80) 1
5
0.2440 (6.20)
4 0.2284 (5.80)
PIN 1
0.0500 (1.27)
BSC
0.0196 (0.50)
0.0099 (0.25) ؋ 45؇
0.0098 (0.25)
0.0040 (0.10)
SEATING
PLANE
0.0688 (1.75)
0.0532 (1.35)
8؇
0.0192 (0.49)
0.0098 (0.25) 0؇
0.0138 (0.35)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
–8– REV. A














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