參數(shù)資料
型號(hào)： LM95214CISD
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類(lèi)： 溫度/濕度傳感器
英文描述： Quad Remote Diode and Local Temperature Sensor with SMBus Interface
中文描述： DIGITAL TEMP SENSOR-SERIAL, 11BIT(s), 2Cel, RECTANGULAR, SURFACE MOUNT
封裝： LLP-14
文件頁(yè)數(shù)： 33/38頁(yè)
文件大小： 448K
代理商： LM95214CISD
3.0 Applications Hints
The LM95214 can be applied easily in the same way as other
integrated-circuit temperature sensors, and its remote diode
sensing capability allows it to be used in new ways as well. It
can be soldered to a printed circuit board, and because the
path of best thermal conductivity is between the die and the
pins, its temperature will effectively be that of the printed cir-
cuit board lands and traces soldered to the LM95214's pins.
This presumes that the ambient air temperature is almost the
same as the surface temperature of the printed circuit board;
if the air temperature is much higher or lower than the surface
temperature, the actual temperature of the LM95214 die will
be at an intermediate temperature between the surface and
air temperatures. Again, the primary thermal conduction path
is through the leads, so the circuit board temperature will con-
tribute to the die temperature much more strongly than will the
air temperature.
To measure temperature external to the LM95214's die, in-
corporates remote diode sensing technology. This diode can
be located on the die of a target IC, allowing measurement of
the IC's temperature, independent of the LM95214's temper-
ature. A discrete diode can also be used to sense the tem-
perature of external objects or ambient air. Remember that a
discrete diode's temperature will be affected, and often dom-
inated, by the temperature of its leads. Most silicon diodes do
not lend themselves well to this application. It is recommend-
ed that an MMBT3904 transistor base emitter junction be
used with the collector tied to the base.
The LM95214 can measure a diode-connected transistor
such as the MMBT3904 or the thermal diode found in an AMD
processor. The LM95214 has been optimized to measure the
MMBT3904 remote thermal diode the offset register can be
used to calibrate for other thermal diodes easily. The
LM95214 does not include TruTherm technology that al-
lows sensing of sub-micron geometry process thermal
diodes. For this application the LM95234 would be better suit-
ed.
The LM95234 has been specifically optimized to measure the
remote thermal diode integrated in a typical Intel processor
on 65 nm or 90 nm process or an MMBT3904 transistor. Using
the Remote Diode Model Select register found in the
LM95234 any of the four remote inputs can be optimized for
a typical Intel processor on 65 nm or 90 nm process or an
MMBT3904.
3.1 DIODE NON-IDEALITY
3.1.1 Diode Non-Ideality Factor Effect on Accuracy
When a transistor is connected as a diode, the following re-
lationship holds for variables V
BE
, T and I
F
:
(1)
where:
q = 1.6×10
19
Coulombs (the electron charge),
T = Absolute Temperature in Kelvin
k = 1.38×10
23
joules/K (Boltzmann's constant),
η
is the non-ideality factor of the process the diode is
manufactured on,
I
S
= Saturation Current and is process dependent,
I
f
= Forward Current through the base-emitter junction
V
BE
= Base-Emitter Voltage drop
In the active region, the -1 term is negligible and may be elim-
inated, yielding the following equation
(2)
In
Equation 2
, η
and I
are dependant upon the process that
was used in the fabrication of the particular diode. By forcing
two currents with a very controlled ratio(I
/ I
) and measur-
ing the resulting voltage difference, it is possible to eliminate
the I
term. Solving for the forward voltage difference yields
the relationship:
(3)
Solving
Equation 3
for temperature yields:
(4)
Equation 4
holds true when a diode connected transistor such
as the MMBT3904 is used. When this “diode” equation is ap-
plied to an integrated diode such as a processor transistor
with its collector tied to GND as shown in
Figure 9
it will yield
a wide non-ideality spread. This wide non-ideality spread is
not due to true process variation but due to the fact that
Equation 4
is an approximation.
National invented TruTherm beta cancellation technology that
uses the transistor equation,
Equation 5
, which is a more ac-
curate representation of the topology of the thermal diode
found in some sub-micron FPGAs or processors.
(5)
33
www.national.com
L
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM95214CISD/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
LM95214CISDX 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
LM95214CISDX/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
LM95214EB/NOPB 功能描述:溫度傳感器開(kāi)發(fā)工具 LM95214EVAL BOARD RoHS:否 制造商:Texas Instruments 產(chǎn)品類(lèi)型:Temperature Sensors and Control ICs 工具用于評(píng)估:MSP430G2553 接口類(lèi)型:USB 工作電源電壓: 工作電源電流:
LM95221 制造商:NSC 制造商全稱(chēng):National Semiconductor 功能描述:Dual Remote Diode Digital Temperature Sensor with SMBus Interface
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