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參數(shù)資料
| 型號： | ASC7521AM8 |
| 廠商： | Electronic Theatre Controls, Inc. |
| 元件分類： | 溫度/濕度傳感器 |
| 英文描述： | LOW- OLTAGE 1-WIRE DIGITAL TEMPERATURE SENSOR |
| 中文描述： | 低OLTAGE 1 - Wire數(shù)字溫度傳感器 |
| 文件頁數(shù)： | 13/18頁 |
| 文件大小： | 186K |
| 代理商： | ASC7521AM8 |
- 13 -
Andigilog, Inc. 2006
www.andigilog.com
October 2006 - 70A05011
aSC7521A
Applications Information
Remote Diodes
The aSC7521A is designed to work with a variety of remote
sensors in the form of a diode-connected transistor or the
substrate thermal diode of a CPU or graphics controller.
Actual diodes are not suited for these measurements.
There is some variation in the performance of these diodes,
described in terms of its departure from the ideal diode
equation. This factor is called diode non-ideality,
.
nf
The equation relating diode temperature to a change in
thermal diode voltage with two driving currents is:
Δ
V
BE
=
(nf )KT
q
ln(N)
where:
nf
= Pentium 4, 65nM non-ideality factor, (nominal 1.009).
K
= Boltzman’s constant, (1.38 x 10
-23
).
T
= diode junction temperature in Kelvins.
q
= electron charge (1.6 x 10
Coulombs).
N
= ratio of the two driving currents (10).
The aSC7521A is designed and trimmed for an expected
value of 1.009, based on the typical value for the Pentium 4,
65nM. There is also a tolerance on the value provided. The
values for CPUs may have different nominal values and
tolerances. Consult the CPU or GPU manufacturer’s data
sheet for the
factor.
nf
Table 5 gives a representative
sample of what one may expect in the range of non-ideality.
The trend with CPUs is for a lower value with a larger spread.
nf
When thermal diode has a non-ideality factor other than
1.0046 the difference in temperature reading at a particular
temperature may be interpreted with the following equation:
=
actual
n
reported
T
actual
T
009
.
where:
T
reported
T
n
Temperatures are in Kelvins or °C + 273.15.
= reported temperature in temperature register.
actual
= actual remote diode temperature.
= selected diode’s non-ideality factor,
actual
.
nf
This equation assumes that the series resistance of the
remote diode 4.52
.
Although the temperature error caused by non-ideality
difference is directly proportional to the difference from 1.009,
but a small difference in non-ideality results in a relatively
large difference in temperature reading. For example, if there
were a ±1% tolerance in the non-Ideality of a diode it would
result in a ±2.7 degree difference (at 0°C) in the result (0.01 x
273.15).
This difference varies with temperature such that a fixed
offset value may only be used over a very narrow range.
Typical correction method required when measuring a wide
range of temperature values is to scale the temperature
reading in the host firmware.
Part
nf
Min
nf
Nom
nf
Max
Series
Res
Pentium III
(CPUID 68h)
Pentium 4,
130nM
Pentium 4, 90nM
Pentium 4, 65nM
Intel Pentium M
2N3904
1.0057
1.008
1.0125
1.001
1.002
1.003
3.64
1.011
1.009
1.0022
1.0046
3.33
4.52
3.06
0.6
1.000
1.0015
1.003
1.050
1.0029
1.005
Table 5 Representative CPU Thermal Diode and
Transistor Non-Ideality Factors
CPU or ASIC Substrate Remote Diodes
A substrate diode is a parasitic PNP transistor that has its
collector tied to ground through the substrate and the base
(D-) and emitter (D+) brought out to pins. Connection to
these pins is shown in Figure 16 CPU Remote Diode
Connection.
The
non-ideality
Representative CPU Thermal Diode and Transistor Non-
Ideality Factors include the effects of any package resistance
and represent the value seen from the CPU socket. The
temperature indicated will need to be compensated for the
departure from a non-ideality of 1.0046 and series resistance
of 0.6
.
figures
in
Table
5
Figure 16 CPU Remote Diode Connection
Discrete Remote Diodes
When sensing temperatures other than the CPU or GPU
substrate, an NPN or PNP transistor may be used. Most
commonly used are the 2N3904 and 2N3906. These have
characteristics similar to the CPU substrate diode with non-
ideality around 1.0046. They are connected with base to
collector shorted as shown in Figure 17 Discrete Remote
Diode Connection.
D+
D-
CPU
aSC7521
Substrate
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相關(guān)代理商/技術(shù)參數(shù) |
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| ASC7531A | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LOW-VOLTAGE 1-WIRE DIGITAL TEMPERATURE SENSOR AND VOLTAGE MONITOR |
| ASC7531AM10 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LOW-VOLTAGE 1-WIRE DIGITAL TEMPERATURE SENSOR AND VOLTAGE MONITOR |
| ASC7531B | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LOW-VOLTAGE 1-WIRE DIGITAL TEMPERATURE SENSOR AND VOLTAGE MONITOR |
| ASC7531BM10 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:LOW-VOLTAGE 1-WIRE DIGITAL TEMPERATURE SENSOR AND VOLTAGE MONITOR |
| ASC7611 | 制造商:未知廠家 制造商全稱:未知廠家 功能描述:HARDWARE MONITOR WITH INTEGRATED FAN CONTROL |
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