ADM1023ARQ 查看數據表（PDF） - Analog Devices
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ADM1023ARQ Datasheet PDF : 12 Pages
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ADM1023
In general, this additional temperature error of the thermal diode
measurement due to deviations on n from its typical value is
given by,
∆T
=
n – 1.008
1.008
× (273.15
Kelvin
+ TTD ), where TTD
is
in
°C
BETA OF THERMAL TRANSISTOR ()
On Figure 12, 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 cur-
rents scaled by “N” as the emitter currents were also scaled by
“N.” In other words, this assumes that beta (β) of the transistor
is constant for various collector currents. The plot below shows
typical beta variation versus collector current for Pentium III
Processors at 100°C. The maximum beta is 4.5 and varies less
than 1% over the collector current range from 7 µA to 300 µA.
MAX < 4.5

IE
⌬

IC = +1 IE
7
300 IC (mA)
Figure 13. Variation of β with Collector Currents
Expressing the collector current in terms of the emitter current,
IC = IE [β/β + 1)] where β(300 µA) = β(7 µA)(1 + ε ), ε = ∆β/β
and β = β (7 µA). Rewriting the equation for ∆VBE, to include
the ideality factor “n” and beta “β” we have,
∆VBE
=
nKT
q
×
ln(1(+1
ε) ×
+ ε)
(β + 1)
β +1
×
N
(3)
Beta variations of less than 1% (ε < 0.01) contribute to tempera-
ture errors of less than 0.4°C.
TEMPERATURE DATA FORMAT
One LSB of the ADC corresponds to 0.125°C, so the ADM1023
can measure from 0°C to 127.875°C. The temperature data for-
mat is shown in Tables I and II.
Table I. Temperature Data Format (Local Temperature
and Remote Temperature High Byte)
Temperature (؇C) Digital Output
0
0 000 0000
1
0 000 0001
10
0 000 1010
25
0 001 1001
50
0 011 0010
75
0 100 1011
100
0 110 0100
125
0 111 1101
127
0 111 1111
Note: The ADM1023 differs from the ADM1021 in that the tem-
perature resolution of the remote channel is improved from 1°C
to 0.125°C, but it cannot measure temperatures below 0°C. If
negative temperature measurement is required, the ADM1021
should be used.
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)
Extended
Resolution (؇C)
0.000
0.125
0.250
0.375
0.500
0.625
0.750
0.875
Remote Temperature
Low Byte
0000 0000
0010 0000
0100 0000
0110 0000
1000 0000
1010 0000
1100 0000
1110 0000
REGISTER FUNCTIONS
The 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 Register
The 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 Registers
The 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 Register
Two 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.
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
temperature. These registers default to zero at power-up and
will have no effect if nothing is written to them. The offset regis-
ter can accept values from –128.875°C to +127.875°C. The
ADM1023 detects overflow so the remote temperature value
register won’t wrap around +127°C or –128°C. Table IV con-
tains a set of example offset values.
REV. A
–7–
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