Precision Dual Voltage
Regulator Controllers
a
ADM1051/ADM1051A
GENERAL DESCRIPTION
FEATURES
The ADM1051/ADM1051A are dual, precision, voltage regula-
tor controllers intended for power rail generation and active bus
termination on personal computer motherboards. They contain a
precision 1.2 V bandgap reference and two channels consisting of
control 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
shutdown input on the 1.5 V channel can also be used with the
TYPEDET signal on a PC motherboard to select the output voltage.
Two Independent Controllers on One Chip
1.515 V and 1.818 V Outputs
Shutdown Inputs to Control Each Channel
Compatible with PC Motherboard TYPEDET Signal
؎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
1.8 V/3.3 V ICH Sequenced Power-Up on ADM1051A
Small, 8-Lead SOIC Package
The ADM1051/ADM1051A operate from a 12 V supply, which
gives sufficient 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.
APPLICATIONS
Desktop Computers
Servers
Workstations
FUNCTIONAL BLOCK DIAGRAM
V
V
IN
3.3V
CC
CONTROL
AMPLIFIER
100F
ADM1051/ADM1051A
BANDGAP
FORCE 1
SENSE 1
REFERENCE
V
CC
V
OUT1
50A
SHUTDOWN
CONTROL
SHDN1
HICCUP
COMPARATOR
V
IN
3.3V
CONTROL
AMPLIFIER
100F
FORCE 2
SENSE 2
NO CONNECTION
ON ADM1051A
V
CC
V
OUT2
50A
SHUTDOWN
CONTROL
SHDN2
HICCUP
COMPARATOR
V
CC
POWER-ON
RESET
CLK/DELAY
GENERATOR
CLOCK
OSCILLATOR
GND
REV. 0
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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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© Analog Devices, Inc., 2000