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a

ADM1051/ADM1051A

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., 2000

Precision Dual Voltage

Regulator Controllers

FUNCTIONAL BLOCK DIAGRAM

SHDN1

50 A

BANDGAP

REFERENCE

HICCUP

COMPARATOR

100 F

2 100 F

CONTROL

AMPLIFIER

FORCE 1

SENSE 1

ADM1051/ADM1051A

SHDN2

HICCUP

COMPARATOR

GND

3.3V

CONTROL

AMPLIFIER

FORCE 2

SENSE 2

SHUTDOWN

CONTROL

100 F

2 100 F

3.3V

SHUTDOWN

CONTROL

50 A

CLK/DELAY

GENERATOR

POWER-ON

RESET

CLOCK

OSCILLATOR

NO CONNECTION

ON ADM1051A

FEATURES

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

APPLICATIONS

Desktop Computers

Servers

Workstations

GENERAL DESCRIPTION

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.

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.