ADM1023ARQ-REEL7 ,±1°C Remote Sensor for Next Generation PIII 700 MHz+ PlatformsCHARACTERISTICSsensor16-Lead QSOP Package4D–Negative connection to remote tempera-q = 105∞C/WJAture ..
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AH101-G , Medium Power, High Linearity Amplifier
AH101-G , Medium Power, High Linearity Amplifier
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ADM1023ARQ-REEL-ADM1023ARQ-REEL7-ADM1023ARQZ
±1°C Remote Sensor for Next Generation PIII 700 MHz+ Platforms
REV.F
FUNCTIONAL BLOCK DIAGRAM
ACPI Compliant
High Accuracy Microprocessor
System Temperature Monitor
FEATURES
Next-Generation Upgrade of 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 DESCRIPTIONThe ADM1023 is a 2-channel digital thermometer and under/over
temperature alarm, intended for use in personal computers and
other systems requiring thermal monitoring and management. Opti-
mized 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 tempera-
ture of a microprocessor using a diode-connected 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 can-
cels 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 temperature of the device and its environment.
The ADM1023 communicates over a 2-wire serial interface com-
patible with SMBus standards. Under and over temperature 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
ADM1023–SPECIFICATIONS(TA = TMIN to TMAX1, VDD = 3.0 V to 3.6 V, unless otherwise noted.)SMBus INTERFACE
NOTES
1TMAX = 120∞C, TMIN = 0∞C.
2TD is temperature of remote thermal diode; TA, TD = 60∞C to 100∞C.
3Operation at VDD = 5 V guaranteed by design, not production tested.
4Guaranteed 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 CHARACTERISTICS16-Lead QSOP PackageqJA = 105∞C/WqJC = 39∞C/W
PIN CONFIGURATION
PIN FUNCTION DESCRIPTIONSFigure 1.Diagram for Serial Bus Timing
CAUTIONESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000V readily
ADM1023
–Typical Performance Characteristics
LEAKAGE RESISTANCE – M�
TEMPERATURE ERROR – 1
–30TPC 1.Temperature Error vs. Resistance from Track
to VDD and GND
FREQUENCY – Hz
TEMPERATURE ERROR – 10k100k1M10M100MTPC 2.Remote Temperature Error vs. Supply Noise
Frequency
FREQUENCY – Hz
TEMPERATURE ERROR – 1k10k10M100M
100100k1MTPC 3.Temperature Error vs. Common-Mode Noise
Frequency
TEMPERATURE – �C
TEMPERATURE ERROR – 708090110120
100TPC 4.Temperature Error of ADM1023 vs.
PentiumIII Temperature
CAPACITANCE – nF
TEMPERATURE ERROR – 81012141618202224TPC 5.Temperature Error vs. Capacitance Between
D+ and D–
SCLK FREQUENCY – kHz
SUPPLY CURRENT –
5102550751001000250500750TPC 6.Standby Supply Current vs. SCLK Frequency
FREQUENCY – Hz
TEMPERATURE ERROR –
100k1M10M100M1GTPC 7.Temperature Error vs. Differential-Mode Noise
Frequency
TPC 8.Operating Supply Current vs. Conversion Rate,
VDD = 5 V and 3 V
FUNCTIONAL DESCRIPTIONThe ADM1023 contains a 2-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 oper-
ating 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 8 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 regis-
ters. The 8 MSBs are stored in the Remote Temperature Value
High Byte Register at address 01h. The 3 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
An offset value may automatically be added to or subtracted from
the measurement by writing an 11-bit, twos complement 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 con-
figured, via the serial System Management Bus. The contents of
any register can also be read back via the SMBus.
Control and configuration functions consist of:
SUPPLY VOLTAGE – V
SUPPLY CURRENT –
–20TPC 9.Standby Supply Current vs. Supply Voltage
TPC 10.Response to Thermal Shock
ADM1023On initial power-up the remote and local temperature values default
to –128∞C. Since the device normally powers up converting, a mea-
sure of local and remote temperature is made and these 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 com-
parison 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 METHODA 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 tempera-
(1)
Unfortunately, this technique requires calibration to null out
the effect of the absolute value of VBE, which varies from devicedevice.
The technique used in the ADM1023 is to measure the change in
VBE when the device is operated at two different collector currents.(2)
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
currents 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
cycles. Signal conditioning and measurement of the internal tem-
perature sensor is performed in a similar manner.
Figure 2 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 tempera-
ture 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 internal 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 Consider-
ations for more information on C1.
SOURCES OF ERRORS ON THERMAL TRANSISTOR
MEASUREMENT METHOD
The Effect of Ideality Factor (n)The effects of ideality factor (n) and beta (b) of the temperature
measured by a thermal transistor are discussed below. For a thermal
transistor implemented on a submicron process, such as the sub-
strate 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 substrate PNP
transistor (used as a thermal diode) usually found on CPUs designed
on submicron CMOS processes such as the PentiumIII 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 specifications,
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 at TTD = 100∞C,
Figure 2.Input Signal Conditioning
In general, this additional temperature error of the thermal diode
measurement due to deviations on n from its typical value is
BETA OF THERMAL TRANSISTOR (�)In Figure 2, the thermal diode is a substrate PNP transistor where
the emitter current is being forced into the device. The derivation
of Equation 2 above assumed that the collector currents scaled
by “N” as the emitter currents were also scaled by “N.” In other
words, this assumes that beta (b) of the transistor is constant for
various collector currents. Figure 3 shows typical b variation versus
collector current for Pentium III processors at 100∞C. The maxi-
mum b is 4.5 and varies less than 1% over the collector current
range from 7 mA to 300 mA.
Figure 3.Variation of b with Collector Currents
Expressing the collector current in terms of the emitter current,
IC = IE [b/(b + 1)] where b(300 mA) = b(7 mA)(1 + e ), e = Db/b
and b = b (7 mA). Rewriting the equation for DVBE, to include(3)
b variations of less than 1% (e < 0.01) contribute to temperature
errors of less than 0.4∞C.
TEMPERATURE DATA FORMATOne LSB of the ADC corresponds to 0.125∞C, so the ADM1023
can measure from 0∞C to 127.875∞C. The temperature data format
and extended temperature resolution are shown in Tables I and II.
Table I.Temperature Data Format (Local
Temperature and Remote Temperature High Byte)00 000 0000
10 000 0001
*The ADM1023 differs from the ADM1021 in that the
The results of the local and remote temperature measurements
are stored in the local and remote temperature value registers
and are compared with limits programmed into the local and
remote high and low limit registers.
Table II.Extended Temperature Resolution
(Remote Temperature Low Byte)
REGISTER FUNCTIONSThe ADM1023 contains registers that are used to store the
results of remote and local temperature measurements, high and
low temperature limits, and to configure and control the device.
A description of these registers follows, and further details are
given in Tables III to VII. It should be noted that most of the
ADM1023’s registers are dual port and have different addresses
for read and write operations. Attempting to write to a read
address, or to read from a write address, will produce an invalid
result. Register addresses above 14h are reserved for future use
or used for factory test purposes and should not be written to.
Address Pointer RegisterThe Address Pointer Register itself does not have, nor does it
require, an address, as it is the register to which the first data
byte of every write operation is written automatically. This data
byte is an address pointer that sets up one of the other registers
for the second byte of the write operation, or for a subsequent
read operation.
Value RegistersThe ADM1023 has three registers to store the results of Local
and Remote temperature measurements. These registers are
written to by the ADC and can only be read over the SMBus.
The Offset RegisterTwo offset registers are provided at addresses 11h and 12h. These
are provided so that the user may remove errors from the measured
values of remote temperature. These errors may be introduced
by clock noise and PCB track resistance. TableIV contains a set
of example offset values.
The offset value is stored as an 11-bit, two’s complement value in
Registers 11h (high byte) and 12h (low byte, left-justified). The
value of the offset is negative if the MSB of 11h is 1 and is positive
if the MSB of 11h is 0. This value is added to the remote tempera-
ture. These registers default to zero at power-up and will have no
effect if nothing is written to them. The offset register can accept
values from –128.875∞C to +127.875∞C. The ADM1023 detects
overflow so the remote temperature value register will not wrap
around +127∞C or –128∞C.
ADM1023
Table IV.Offset Values
Status RegisterBit 7 of the Status Register (see Table V) indicates that the ADC
is busy converting when it is high. Bits 6 to 3 are flags that indicate
the results of the limit comparisons.
If the local and/or remote temperature measurement is above
the corresponding high temperature limit, or below the corre-
sponding low temperature limit, one or more of these flags will be
set. Bit2 is a flag that is set if the remote temperature sensor is
open-circuit. These five flags are NOR’d together, so that if any
of them are high, the ALERT interrupt latch will be set and the
ALERT output will go low. Reading the Status Register will clear
the five flag bits, provided the error conditions that caused the
flags to be set have gone away. While a limit comparator is tripped
due to a value register containing an out-of-limit measurement,
be reset. A flag bit can only be reset if the corresponding value
register contains an in-limit measurement, or the sensor is good.
The ALERT interrupt latch is not reset by reading the Status
Register, but will be reset when the ALERT output has been
serviced by the master reading the device address, provided the
error condition has gone away and the Status Register flag bits
have been reset.
Table V.Status Register Bit Assignments*These flags stay high until the status register is read or they are reset by POR.
Configuration RegisterTwo bits of the configuration register are used. If Bit 6 is 0, which
is the power-on default, the device is in operating mode with the
ADC converting (see Table VI). If Bit 6 is set to 1, the device is in
standby mode and the ADC does not convert. Standby mode can
also be selected by taking the STBY pin low. In standby mode the
values of remote and local temperature remain at the value they
were before the part was placed in standby.
Bit 7 of the configuration register is used to mask the ALERT out-
put. If Bit 7 is 0, which is the power-on default, the ALERT output
is enabled. If Bit 7 is set to 1, the ALERT output is disabled.
Table III.List of ADM1023 Registers*Writing to address 0F causes the ADM1023 to perform a single measurement. It is not a data register as such and it does not matter what data is written to it.
