ADM1024
26.5
26.0
Pins 15, 16, and 19 are dedicated analog inputs with on-chip
attenuators, configured to monitor 12 V, 5 V and the processor
core voltage, respectively.
V
DD
= 3.3V
SHUTDOWN CURRENT – A
25.5
25.0
24.5
24.0
23.5
23.0
22.5
–40
Pins 17 and 18 may be configured as analog inputs with on-chip
attenuators to monitor a second processor core voltage and a
2.5 V supply, or they may be configured as a temperature input
and connected to a second temperature-sensing diode.
The ADC also accepts input from an on-chip bandgap tempera-
ture sensor that monitors system-ambient temperature.
Finally, the ADM1024 monitors the supply from which it is
powered, so there is no need for a separate 3.3 V analog input,
if the chip V
CC
is 3.3 V. The range of this V
CC
measurement
can be configured for either a 3.3 V or 5 V V
CC
by Bit 3 of the
Channel Mode Register.
SEQUENTIAL MEASUREMENT
–20
0
20
40
60
80
TEMPERATURE – C
100
120
Figure 8. Standby Current vs. Temperature
(continued from page 1)
configured as inputs to monitor a 2.5 V supply and a second
processor core voltage, or as a second temperature sensing input.
The remaining two inputs can be programmed as general-purpose
analog inputs or as digital fan-speed measuring inputs.
Measured values can be read out via an SMBus serial System
Management Bus, and values for limit comparisons can be
programmed in over the same serial bus. The high-speed
successive-approximation ADC allows frequent sampling of
all analog channels to ensure a fast interrupt response to any
out-of-limit measurement.
The ADM1024’s 2.8 V to 5.5 V supply voltage range, low supply
current, and SMBus interface make it ideal for a wide range
of applications. These include hardware monitoring and protec-
tion applications in personal computers, electronic test equipment,
and office electronics.
GENERAL DESCRIPTION
When the ADM1024 monitoring sequence is started, it cycles
sequentially through the measurement of analog inputs and the
temperature sensor, while at the same time the fan speed inputs
are independently monitored. Measured values from these inputs
are stored in Value Registers. These can be read out over the
serial bus, or can be compared with programmed limits stored in
the Limit Registers. The results of out-of-limit comparisons are
stored in the Interrupt Status Registers, and will generate an
interrupt on the
INT
line (Pin 10).
Any or all of the Interrupt Status Bits can be masked by appro-
priate programming of the Interrupt Mask Register.
PROCESSOR VOLTAGE ID
Five digital inputs (VID4 to VID0—Pins 20 to 24) read the
processor voltage ID code. These inputs can also be reconfigured
as interrupt inputs.
The VID pins have internal 100 k pull-up resistors.
CHASSIS INTRUSION
The ADM1024 is a complete system hardware monitor for
microprocessor-based systems. The device communicates with
the system via a serial System Management Bus. The serial bus
controller has a hardwired address line for device selection (Pin
1), a serial data line for reading and writing addresses and data
(Pin 3), and an input line for the serial clock (Pin 4). All control
and programming functions of the ADM1024 are performed over
the serial bus.
MEASUREMENT INPUTS
A chassis intrusion input (Pin 7) is provided to detect unauthorized
tampering with the equipment.
RESET
A
RESET
input/output (Pin 12) is provided. Pulling this pin low
will reset all ADM1024 internal registers to default values. The
ADM1024 can also be programmed to give a low-going 45 ms
reset pulse at this pin.
The
RESET
pin has an internal, 100 kΩ pull-up resistor.
Programmability of the measurement inputs makes the ADM1024
extremely flexible and versatile. The device has a 10-bit A-to-D
converter, and nine measurement input pins that can be configured
in different ways.
Pins 5 and 6 can be programmed as general-purpose analog
inputs with a range of 0 V to 2.5 V, or as digital inputs to
monitor the speed of fans with digital tachometer outputs. The
fan inputs can be programmed to accommodate fans with dif-
ferent speeds and different numbers of pulses per revolution from
their tach outputs.
Pins 13 and 14 are dedicated temperature inputs and may be
connected to the cathode and anode of an external temperature-
sensing diode.
ANALOG OUTPUT
The ADM1024 contains an on-chip, 8-bit digital-to-analog
converter with an output range of zero to 2.5 V (Pin 11). This is
typically used to implement a temperature-controlled fan by
controlling the speed of a fan dependent upon the temperature
measured by the on-chip temperature sensor.
Testing of board level connectivity is simplified by providing a
NAND tree test function. The AOUT (Pin 11) also doubles as
a NAND test input, while Pin 1 doubles as a NAND tree output.
INTERNAL REGISTERS OF THE ADM1024
A brief description of the ADM1024’s principal internal regis-
ters is given below. More detailed information on the function
of each register is given in Tables VI to XIX.
–7–
REV. 0
AD [ ANALOG DEVICES ]
