參數(shù)資料
型號(hào)： LM95235
廠商： National Semiconductor Corporation
元件分類(lèi)： 溫度/濕度傳感器
英文描述： Precision Remote Diode Temperature Sensor with SMBus Interface and TruTherm Technology
中文描述： 高精度遠(yuǎn)程二極管溫度傳感器，帶有SMBus接口和TruTherm技術(shù)
文件頁(yè)數(shù)： 22/25頁(yè)
文件大?。?/td> 784K
代理商： LM95235
3.0 Applications Hints
(Continued)
TruTherm should only be enabled when measuring the tem-
perature of a transistor integrated as shown in the processor
of
Figure 7
, because
Equation (5)
only applies to this topol-
ogy.
3.1.2 Calculating Total System Accuracy
The voltage seen by the LM95235 also includes the I
R
S
voltage drop of the series resistance. The non-ideality factor,
η
, is the only other parameter not accounted for and de-
pends on the diode that is used for measurement. Since
V
is proportional to both
η
and T, the variations in
η
cannot be distinguished from variations in temperature.
Since the non-ideality factor is not controlled by the tempera-
ture sensor, it will directly add to the inaccuracy of the
sensor. For the for Intel processor on 65nm process, Intel
specifies a +4.06%/0.897% variation in
η
from part to part
when the processor diode is measured by a circuit that
assumes diode equation,
Equation (4)
, as true. As an ex-
ample, assume a temperature sensor has an accuracy
specification of
±
1.0C at a temperature of 80C (353 Kelvin)
and the processor diode has a non-ideality variation of
+1.19%/0.27%. The resulting system accuracy of the pro-
cessor temperature being sensed will be:
T
ACC
= + 1.0C + (+4.06% of 353 K) = +15.3 C
and
T
ACC
= - 1.0C + (0.89% of 353 K) = 4.1 C
TrueTherm technology uses the transistor equation,
Equa-
tion (5)
, resulting in a non-ideality spread that truly reflects
the process variation which is very small. The transistor
equation non-ideality spread is
±
0.39% for the Pentium 4
processor on 90 nm process. The resulting accuracy when
using TruTherm technology improves to:
T
ACC
=
±
0.75C + (
±
0.39% of 353 K) =
±
2.16 C
The next error term to be discussed is that due to the series
resistance of the thermal diode and printed circuit board
traces. The thermal diode series resistance is specified on
most processor data sheets. For Intel processors in 65 nm
process, this is specified at 4.52
typical. The LM95235
accommodates the typical series resistance of Intel Proces-
sor on 65 nm process. The error that is not accounted for is
the spread of the processor’s series resistance, that is 2.79
to 6.24
or
±
1.73
. The equation to calculate the tempera-
ture error due to series resistance (T
ER
) for the LM95235 is
simply:
(6)
Solving
Equation (6)
for R
equal to
±
1.73
results in the
additional error due to the spread in the series resistance of
±
1.07C. The spread in error cannot be canceled out, as it
would require measuring each individual thermal diode de-
vice. This is quite difficult and impractical in a large volume
production environment.
Equation (6)
can also be used to calculate the additional
error caused by series resistance on the printed circuit
board. Since the variation of the PCB series resistance is
minimal, the bulk of the error term is always positive and can
simply be cancelled out by subtracting it from the output
readings of the LM95235.
Processor Family
Intel Processor on
65 nm process
Transistor Equation
η
D
,
non-ideality
min
typ
0.997
1.001
Series
R,
max
1.005
4.52
Processor Family
Diode Equation
η
D
,
non-ideality
min
typ
Series
R,
max
Pentium III CPUID
67h
Pentium III CPUID
68h/PGA370Socket/
Celeron
Pentium 4, 423 pin
Pentium 4, 478 pin
1
1.0065
1.0125
1.0057
1.008
1.0125
0.9933
0.9933
1.0045
1.0045
1.0368
1.0368
20174943
FIGURE 7. Thermal Diode Current Paths
L
www.national.com
22
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LM95235_08 制造商:NSC 制造商全稱:National Semiconductor 功能描述:Precision Remote Diode Temperature Sensor with SMBus Interface and TruTherm? Technology
LM95235CIMM 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類(lèi)型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
LM95235CIMM 制造商:Texas Instruments 功能描述:TEMP SENSE REM DIODE SMD MSOP8
LM95235CIMM/NOPB 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類(lèi)型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
LM95235CIMMX 功能描述:板上安裝溫度傳感器 RoHS:否 制造商:Omron Electronics 輸出類(lèi)型:Digital 配置: 準(zhǔn)確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數(shù)字輸出 - 總線接口:2-Wire, I2C, SMBus 電源電壓-最大:5.5 V 電源電壓-最小:4.5 V 最大工作溫度:+ 50 C 最小工作溫度:0 C 關(guān)閉: 安裝風(fēng)格: 封裝 / 箱體: 設(shè)備功能:Temperature and Humidity Sensor
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