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ADM1051AJR-REEL7-ADM1051AJRZ-ADM1051JR-REEL
Precision Dual Voltage Regulator Controllers
REV.0
Precision Dual Voltage
Regulator Controllers
FUNCTIONAL BLOCK DIAGRAM
SHDN1
VOUT1
SHDN2
GND
VCCVIN
3.3V
VOUT2
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 DESCRIPTIONThe 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.
ADM1051/ADM1051A–SPECIFICATIONS
(VCC = 12 V � 6%, VIN = 3.3 V, TA = 0�C to 70�C, both
channels, unless otherwise noted. See Test Circuit.)CONTROL AMPLIFIER
NOTESGuaranteed by design.5 VSB Supply is connected to, and measured at anode of Schottky Diode.
Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*(TA = 25°C unless otherwise noted)
VCC to GND . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14 V
SHDN1, SHDN2 to GND . . . . . . . . –0.3 V to (VCC + 0.3 V)
SENSE 1, SENSE 2 to GND . . . . . . . . . . . –0.3 V to +5.5 V
FORCE 1, FORCE 2 . . . . . . . Short-Circuit to GND or VCC
Continuous Power Dissipation (TA = 70°C) . . . . . . . 650 mW
8-Lead SOIC (Derate 8.3 mW/°C Above 70°C)
Operating Temperature Range
Commercial (J Version) . . . . . . . . . . . . . . . . . . 0°C to 70°C
Storage Temperature Range . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering, 10 sec) . . . . . . . . . . . . 300°C
*This is a stress rating only; functional operation of the device at these or any other
conditions above those indicated in the operation sections of this specification is
not implied. Exposure to absolute maximum rating conditions for extended
periods of time may affect reliability.
THERMAL CHARACTERISTICS8-Lead Small Outline Package:
θJA = 150°C/W
PIN FUNCTION DESCRIPTIONSFigure 1.Test Circuit
PIN CONFIGURATION
CAUTIONESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
accumulate on the human body and test equipment and can discharge without detection.
Although the ADM1051/ADM1051A features proprietary ESD protection circuitry, permanent
damage may occur on devices subjected to high-energy electrostatic discharges. Therefore,
proper ESD precautions are recommended to avoid performance degradation or loss of
functionality.
ADM1051/ADM1051A
–Typical Performance CharacteristicsTPC 1.Line Transient Response, Channel 1 and
Channel 2
TPC 2.Line Regulation, Channel 1
TPC 3.Line Regulation, Channel 2
TPC 4.Load Regulation, Channel 1
CURRENT – A
OUTPUT 1
1.820TPC 5.Load Regulation, Channel 2
FREQUENCY – Hz
RIPPLE REJECTION
dB
1001010k100k10M1k1M
–10TPC 6.VCC Supply Ripple Rejection
TEMPERATURE – �C
OUTPUT
1.75TPC 7.Regulator Output Voltage vs. Temperature
TPC 8.Transient Response Channel 1, 10 mA to 2 A
Output Load Step
TPC 9.Transient Response Channel 1, 2 A to 10 mA
Output Load Step
TPC 10.Transient Response Channel 2, 10 mA to 2 A
Output Load Step
TPC 11.Transient Response Channel 2, 2 A to 10 mA
Output Load Step
TPC 12.Force Output in Hiccup Mode, Channel 1
ADM1051/ADM1051A
GENERAL DESCRIPTIONThe ADM1051/ADM1051A are dual, precision, voltage regulator
controllers intended for power rail generation and active bus ter-
mination in AGP and ICH applications on personal computer
motherboards. They contain a precision 1.2 V bandgap ref-
erence and two almost identical channels consisting of control
amplifiers driving external power devices. The main difference
between the two channels is the regulated output voltage, defined
by the resistor ratios on the voltage sense inputs of each channel.
Channel 1 has an output of nominally 1.515 V, but can be
switched to a 3.3 V output, while Channel 2 has a nominal
output of 1.818 V. Channel 1 is also optimized for driving
MOSFETs with lower on-resistance and higher gate capaci-
tance, as explained later.
Each channel has a shutdown input to turn off amplifier output
and protection circuitry for the external power device. The
shutdown input of Channel 1 has additional functionality as
described later.
The ADM1051A has some minor differences from the ADM1051
to support power-supply sequencing and voltage requirements
of some I/O control hub chipsets, which dictate that the 1.818 V
rail must never be more than 2 V below the 3.3 V rail.
The ADM1051/ADM1051A operates from a 12 V VCC supply.
The outputs are disabled until VCC climbs above the Power-On
Reset threshold (6 V–9 V). POR does not apply to Channel 2 of
the ADM1051A. This output will begin to rise as soon as there
is sufficient gate drive to turn on the external MOSFET.
The outputs from the ADM1051/ADM1051A are used to drive
external N-channel MOSFETs, operating as source-followers.
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.
The external power devices are protected by a “Hiccup Mode”
circuit that operates if the circuit goes out of regulation due to
an output short-circuit. In this case the power device is pulsed
on/off with a 1:40 duty-cycle to limit the power dissipation until
CIRCUIT DESCRIPTION
CONTROL AMPLIFIERSThe reference voltage is amplified and buffered by the control
amplifiers and external MOSFETs, the output voltage of each
channel being determined by the feedback resistor network
between the sense input and the inverting input of the control
amplifier.
The two control amplifiers in the ADM1051/ADM1051A are
almost identical, apart, from the ratios of the feedback resistor
networks on the sense inputs. A power-on reset circuit disables
the amplifier output until VCC has risen above the reset thresh-
old (not Channel 2 of ADM1051A).
Each amplifier output drives the gate of an N-channel power
MOSFET, whose drain is connected to the unregulated supply
input and whose source is the regulated output voltage, which is
also fed back to the appropriate sense input of the ADM1051/
ADM1051A. The control amplifiers have high current-drive
capability so they can quickly charge and discharge the gate
capacitance of the external MOSFET, thus giving good transient
response to changes in load or input voltage. In particular,
Channel 1 is optimized to drive MOSFETs with very low on
resistance and correspondingly higher gate capacitance such as
the PHD55N03LT from Philips. This is to minimize voltage
drop across the MOSFET when Channel 1 is used in 3.3 V
mode, as explained later.
SHUTDOWN INPUTS AND TYPEDET COMPATIBILITYEach channel has a separate shutdown input, which may be
controlled by a logic signal, and allows the output of the regula-
tor to be turned on or off. If the shutdown input is held high or
not connected, the regulator operates normally. If the shutdown
input is held low, the enable input of the control amplifier is turned
off and the amplifier output goes low, turning off the regulator.
The SHDN1 input on Channel 1 has additional functionality that
can be controlled by the TYPEDET signal on PC motherboards.
The AGP bus on a PC motherboard can have two different modes
of operation, requiring different regulated voltages of 3.3 V or
1.5 V. These two modes are signaled by the TYPEDET signal on
5VSB – V
CHANNEL 2O/P
25�C
VCH2 V's 5VSB ILOAD�500m
70�C
0�CTPC 13.ADM1051A Channel 2 Output Voltage vs. 5 VSB
Voltage. Test Circuit as Figure 7, ILOAD = 500 mA
5VSB – V
CHANNEL 2O/P
25�C
0�C
70�C
VCH2 V's 5VSB ILOAD�1TPC 14.ADM1051A Channel 2 Output Voltage vs. 5 VSB
Voltage. Test Circuit as Figure 7, ILOAD = 1 A
