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ADM1023ARQ ,ACPI-Compliant High-Accuracy Microprocessor System Temperature MonitorSPECIFICATIONSA MIN MAX DDParameter Min Typ Max Unit Test Conditions/CommentsPOWER SUPPLY AND ADCTe ..
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ADM1023ARQ
ACPI-Compliant High-Accuracy Microprocessor System Temperature Monitor
REV.A
FUNCTIONAL BLOCK DIAGRAM
ACPI-Compliant
High-Accuracy Microprocessor
System Temperature Monitor
FEATURES
Next Generation Upgrade to ADM1021
On-Chip and Remote Temperature Sensing
Offset Registers for System Calibration
1�C Accuracy and Resolution on Local Channel
0.125�C Resolution/1�C Accuracy on Remote Channel
Programmable Over/Under Temperature Limits
Programmable Conversion Rate
Supports System Management Bus (SMBus) Alert
2-Wire SMBus Serial Interface
200 �A Max Operating Current (0.25 Conversions/
Seconds)
1 �A Standby Current
3 V to 5.5 V Supply
Small 16-Lead QSOP Package
APPLICATIONS
Desktop Computers
Notebook Computers
Smart Batteries
Industrial Controllers
Telecomms Equipment
Instrumentation
PRODUCT DESCRIPTION
The ADM1023 is a two-channel digital thermometer and under/
over temperature alarm, intended for use in personal computers
and other systems requiring thermal monitoring and management.
Optimized for the Pentium® III; the higher accuracy offered
allows systems designers to safely reduce temperature guard
banding and increase system performance. The device can
measure the temperature of a microprocessor using a diode-con-
nected PNP transistor, which may be provided on-chip in the
case of the Pentium III or similar processors, or can be a low
cost discrete NPN/PNP device such as the 2N3904/2N3906.
A novel measurement technique cancels out the absolute value
of the transistor’s base emitter voltage, so that no calibration
is required. The second measurement channel measures the
output of an on-chip temperature sensor, to monitor the tem-
perature of the device and its environment.
The ADM1023 communicates over a 2-wire serial interface
compatible with SMBus standards. Under and over tempera-
ture limits can be programmed into the device over the serial
bus, and an ALERT output signals when the on-chip or remote
temperature is out of range. This output can be used as an
interrupt, or as an SMBus alert.
*Patents pending.
Pentium is a registered trademark of Intel Corporation.
ADM1023–SPECIFICATIONS(TA = TMIN to TMAX1, VDD = 3.0 V to 3.6 V, unless otherwise noted)
NOTESTMAX = 120°C, TMIN = 0°C.TD is temperature of remote thermal diode; TA, TD = 60°C to 100°C.Operation at VDD = 5 V guaranteed by design, not production tested.Guaranteed by design, not production tested.
Speciﬁcations subject to change without notice.
ABSOLUTE MAXIMUM RATINGS*
Positive Supply Voltage (VDD) to GND . . . . . . –0.3 V to +6 V
D+, ADD0, ADD1 . . . . . . . . . . . . . . . –0.3 V to VDD + 0.3 V
D– to GND . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +0.6 V
SCLK, SDATA, ALERT, STBY . . . . . . . . . . . –0.3 V to +6 V
Input Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±50 mA
Input Current, D– . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±1 mA
ESD Rating, all pins (Human Body Model) . . . . . . . . 2000 V
Continuous Power Dissipation
Up to 70°C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 mW
Derating Above 70°C . . . . . . . . . . . . . . . . . . . . . 6.7 mW/°C
Operating Temperature Range . . . . . . . . . . –55°C to +125°C
Maximum Junction Temperature (TJ max) . . . . . . . . . . 150°C
Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C
Lead Temperature (Soldering 10 sec) . . . . . . . . . . . . . . 300°C
IR Reflow Peak Temperature . . . . . . . . . . . . . . . . . . . . . 220°C
*Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. This is a stress rating only; functional operation of the
device at these or any other conditions above those indicated in the operational
section of this speciﬁcation is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
THERMAL CHARACTERISTICS
16-Lead QSOP Package
θJA = 105°C/W
θJC = 39°C/W
PIN FUNCTION DESCRIPTIONS
PIN CONFIGURATION
Figure 1.Diagram for Serial Bus Timing
ADM1023
–Typical Performance Characteristics
LEAKAGE RESISTANCE – M�
TEMPERATURE ERROR
�C1
–30
Figure 2.Temperature Error vs. Resistance from Track to
VDD and GND
FREQUENCY – Hz
TEMPERATURE ERROR
�C10k100k1M10M100M
Figure 3.Remote Temperature Error vs. Supply Noise
Frequency
FREQUENCY – Hz
TEMPERATURE ERROR
�C1k10k10M100M
100100k1M
Figure 4.Temperature Error vs. Common-Mode Noise
Frequency
TEMPERATURE – �C
ERROR 708090110120
100
Figure 5.Temperature Error of ADM1023 vs. Pentium III
Temperature
CAPACITANCE – nF
TEMPERATURE ERROR
�C681012141618202224
Figure 6.Temperature Error vs. Capacitance Between D+
and D–
SCLK FREQUENCY – kHz
SUPPLY CURRENT 102550751001000250500750
Figure 7.Standby Supply Current vs. SCLK Frequency
FREQUENCY – Hz
TEMPERATURE ERROR
�C
100k1M10M100M1G
Figure 8.Temperature Error vs. Differential-Mode Noise
Frequency
Figure 9.Operating Supply Current vs. Conversion Rate,
VDD = 5 V and 3 V
FUNCTIONAL DESCRIPTION
The ADM1023 contains a two-channel, A-to-D converter with
special input-signal conditioning to enable operation with remote
and on-chip diode temperature sensors. When the ADM1023
is operating normally, the A-to-D converter operates in a
free-running mode. The analog input multiplexer alternately
selects either the on-chip temperature sensor to measure its
local temperature, or the remote temperature sensor. These
signals are digitized by the ADC and the results are stored in
the Local and Remote Temperature Value Registers. Only
the eight most signiﬁcant bits of the local temperature value
are stored as an 8-bit binary word. The remote temperature value
is stored as an 11-bit, binary word in two registers. The eight
MSBs are stored in the Remote Temperature Value High Byte
Register at address 01h. The three LSBs are stored, left-justiﬁed,
in the Remote Temperature Value High Byte Register at
address 10h.
Error sources such as PCB track resistance and clock noise
can introduce offset errors into measurements on the Remote
Channel. To achieve the speciﬁed accuracy on this channel,
value to registers 11h (high byte) and 12h (low byte, left-
justiﬁed).
The offset registers default to zero at power-up and will have no
effect if nothing is written to them.
The measurement results are compared with Local and Remote,
High and Low Temperature Limits, stored in six on-chip Limit
Registers. As with the measured value, the local temperature
limits are stored as 8-bit values and the remote temperature limits
as 11-bit values. Out-of-limit comparisons generate flags that
are stored in the status register, and one or more out-of-limit
results will cause the ALERT output to pull low.
Registers can be programmed, and the device controlled and
conﬁgured, via the serial System Management Bus. The con-
tents of any register can also be read back via the SMBus.
Control and conﬁguration functions consist of:Switching the device between normal operation and standby
mode.Masking or enabling the ALERT output.
SUPPLY VOLTAGE – V
SUPPLY CURRENT
–20
Figure 10.Standby Supply Current vs. Supply Voltage
Figure 11.Response to Thermal Shock
ADM1023
values are then stored before a comparison with the stored limits is
made. However, if the part is powered up in standby mode (STBY
pin pulled low), no new values are written to the register before
a comparison is made. As a result, both RLOW and LLOW are
tripped in the Status Register thus generating an ALERT output.
This may be cleared in one of two ways:Change both the local and remote lower limits to –128°C
and read the status register (which in turn clears the ALERT
output).Take the part out of standby and read the status register
(which in turn clears the ALERT output). This will work
only if the measured values are within the limit values.
MEASUREMENT METHOD
A simple method of measuring temperature is to exploit the nega-
tive temperature coefﬁcient of a diode, or the base-emitter voltage
of a transistor, operated at constant current. Thus, the temperature
may be obtained from a direct measurement of VBE where, (1)
Unfortunately, this technique requires calibration to null out
the effect of the absolute value of VBE, which varies from device
to device.
The technique used in the ADM1023 is to measure the change
in VBE when the device is operated at two different collector
currents.
This is given by: (2)
where:
K is Boltzmann’s constant
q is charge on the electron (1.6 × 10–19 Coulombs)
T is absolute temperature in Kelvins
N is ratio of the two collector currents
n is the ideality factor of the thermal diode (TD)
To measure ∆VBE, the sensor is switched between operating cur-
rents of I and NI. The resulting waveform is passed through a
low-pass ﬁlter to remove noise, then to a chopper-stabilized ampli-
ﬁer that performs the functions of ampliﬁcation and rectiﬁcation of
the waveform to produce a dc voltage proportional to ∆VBE. This
voltage is measured by the ADC, which gives a temperature output
Figure 12 shows the input signal conditioning used to measure
the output of an external temperature sensor. This ﬁgure shows
the external sensor as a substrate PNP transistor, provided for
temperature monitoring on some microprocessors, but it could
equally well be a discrete transistor. If a discrete transistor is
used, the collector will not be grounded and should be linked to
the base. To prevent ground noise from interfering with the
measurement, the more negative terminal of the sensor is not
referenced to ground, but is biased above ground by an inter-
nal diode at the D– input. If the sensor is operating in a noisy
environment, C1 may optionally be added as a noise ﬁlter. Its value
is typically 2200pF, but should be no more than 3000pF. See the
section on Layout Considerations for more information on C1.
SOURCES OF ERRORS ON THERMAL
TRANSISTOR MEASUREMENT METHOD
EFFECT OF IDEALITY FACTOR (n)
The effects of ideality factor (n) and beta (Beta) of the temperature
measured by a thermal transistor are discussed below. For a ther-
mal transistor implemented on a submicron process, such as the
substrate PNP used on a Pentium III processor, the temperature
errors due to the combined effect of the ideality factor and beta are
shown to be less than 3°C. Equation 2 is optimized for a sub-
strate PNP transistor (used as a thermal diode) usually found on
CPUs designed on submicron CMOS processes such as the
Pentium III Processor. There is a thermal diode on board each of
these processors. The n in the Equation 2 represents the ideality
factor of this thermal diode. This ideality factor is a measure of the
deviation of the thermal diode from ideal behavior.
According to Pentium III Processor manufacturing specifica-
tions, measured values of n at 100°C are:
nMIN = 1.0057 < nTYPICAL = 1.008 < nMAX = 1.0125
The ADM1023 takes this ideality factor into consideration
when calculating temperature TTD of the thermal diode. The
ADM1023 is optimized for nTYPICAL = 1.008; any deviation
on n from this typical value causes a temperature error that is
calculated below for the nMIN and nMAX of a Pentium III Processor
Figure 12.Input Signal Conditioning

Partno	Mfg	Dc	Qty	Available	Descript
ADM1023ARQ	AD	N/a	145	avai	ACPI-Compliant High-Accuracy Microprocessor System Temperature Monitor