ADM1024ARU datasheet(7/28 Pages) AD

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ADM1024

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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

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

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.

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.

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 VCC is 3.3 V. The range of this VCC measurement

can be conﬁgured for either a 3.3 V or 5 V VCC by Bit 3 of the

Channel Mode Register.

SEQUENTIAL MEASUREMENT

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

A chassis intrusion input (Pin 7) is provided to detect unauthorized

tampering with the equipment.

RESET

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 k

Ω pull-up resistor.

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.

TEMPERATURE – C

26.5

25.0

22.5

–40

–20

100

120

26.0

25.5

24.5

VDD = 3.3V

24.0

23.5

23.0

Figure 8. Standby Current vs. Temperature

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