ADM1031 datasheet(9/32 Pages) AD

9 / 32 page

REV. 0

ADM1031

–9–

ALERT RESPONSE ADDRESS

Alert Response Address (ARA) is a feature of SMBus devices

that allows an interrupting device to identify itself to the host

when multiple devices exist on the same bus.

The

INT output can be used as an interrupt output or can be used

as an

SMBALERT. One or more INT outputs can be connected

to a common

SMBALERT line connected to the master. If a

device’s

INT line goes low, the following procedure occurs:

SMBALERT pulled low.

2. Master initiates a read operation and sends the Alert

Response Address (ARA = 0001 100). This is a general call

address that must not be used as a specific device address.

3. The device whose

INT output is low responds to the Alert

Response Address, and the master reads its device address.

The address of the device is now known and can be interro-

gated in the usual way.

4. If more than one device’s

INT output is low, the one with

the lowest device address will have priority, in accordance

with normal SMBus arbitration.

5. Once the ADM1031 has responded to the Alert Response

Address, it will reset its

INT output; however, if the error

condition that caused the interrupt persists,

INT will be

reasserted on the next monitoring cycle.

TEMPERATURE MEASUREMENT SYSTEM

Internal Temperature Measurement

The ADM1031 contains an on-chip bandgap temperature sen-

sor. The on-chip ADC performs conversions on the output of

this sensor and outputs the temperature data in 10-bit two’s

complement format. The resolution of the local temperature

sensor is 0.25

°C. The format of the temperature data is shown

in Table II.

External Temperature Measurement

The ADM1031 can measure the temperatures of two external

diode sensors or diode-connected transistors, connected to Pins

9 and 10 and Pins 11 and 12.

These pins are dedicated temperature input channels. The

function of Pin 7 is as a

THERM input/output and is used to

flag overtemperature conditions.

The forward voltage of a diode or diode-connected transistor,

operated at a constant current, exhibits a negative temperature

coefficient of about –2 mV/

°C. Unfortunately, the absolute

value of VBE, varies from device to device, and individual

calibration is required to null this out, so the technique is

unsuitable for mass production.

The technique used in the ADM1031 is to measure the change

in VBE when the device is operated at two different currents.

This is given by:

∆V

BE = KT/q

× ln (N)

where:

K is Boltzmann’s constant.

q is charge on the carrier.

T is absolute temperature in Kelvins.

N is ratio of the two currents.

Figure 3 shows the input signal conditioning used to measure

the output of an external temperature sensor. This figure shows

the external sensor as a substrate transistor, provided for tempera-

ture monitoring on some microprocessors, but it could equally

well be a discrete transistor.

LOW-PASS

FILTER

fC = 65kHz

BIAS

DIODE

REMOTE

SENSING

TRANSISTOR

IIBIAS

D+

D–

VOUT+

VOUT–

ADC

VDD

Figure 3. Signal Conditioning

If a discrete transistor is used, the collector will not be grounded,

and should be linked to the base. If a PNP transistor is used, the

base is connected to the D– input and the emitter to the D+

input. If an NPN transistor is used, the emitter is connected to

the D– input and the base to the D+ input.

One LSB of the ADC corresponds to 0.125

°C, so the ADM1031

can theoretically measure temperatures from –127

°C to +127.75°C,

although –127

°C is outside the operating range for the device.

The extended temperature resolution data format is shown in

Tables III and IV.

Table II. Temperature Data Format (Local Temperature

and Remote Temperature High Bytes)

Temperature ( C)

Digital Output

–128

°C

1000 0000

–125

°C

1000 0011

–100

°C

1001 1100

–75

°C

1011 0101

–50

°C

1100 1110

–25

°C

1110 0111

–1

°C

1111 1111

°C

0000 0000

°C

0000 0001

+10

°C

0000 1010

+25

°C

0001 1001

+50

°C

0011 0010

+75

°C

0100 1011

+100

°C

0110 0100

+125

°C

0111 1101

+127

°C

0111 1111

ADM1031 Datasheet(PDF) 9 Page - Analog Devices

ADM1031 Datasheet(HTML) 9 Page - Analog Devices

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32

Datasheet Download

Link URL