參數(shù)資料
型號(hào)： TMP435ADGST
廠商： TEXAS INSTRUMENTS INC
元件分類： 模擬信號(hào)調(diào)理
英文描述： SPECIALTY ANALOG CIRCUIT, PDSO10
封裝： GREEN, PLASTIC, MSOP-10
文件頁數(shù)： 19/31頁
文件大?。?/td> 477K
代理商： TMP435ADGST
T
=
ERR
°
[273.15+T( C)]
n
1.008
-
(
)
T
=
ERR
°
(273.15+100 C)
1.004
1.008
-
(
)
T
=1.48 C
ERR
°
SBOS495A – MARCH 2010 – REVISED APRIL 2010
www.ti.com
Remote Sensing
3. Base resistance < 100
.
4. Tight control of VBE characteristics indicated by
The TMP435 is designed to be used with either
small variations in hFE (that is, 50 to 150).
discrete transistors or substrate transistors built into
processor chips and ASICs. Either NPN- or PNP-type
Based
on
these
criteria,
two
recommended
transistors can be used, as long as the base-emitter
small-signal transistors are the 2N3904 (NPN) or
junction is used as the remote temperature sense.
2N3906 (PNP).
NPN transistors must be diode-connected. PNP
transistors
can
either
be
transistor-
or
Measurement Accuracy and Thermal
diode-connected (see Figure 13).
Considerations
Errors in remote temperature sensor readings are
The temperature measurement accuracy of the
typically the consequence of the ideality factor and
TMP435
depends
on
the
remote
and/or
local
current excitation used by the TMP435 versus the
temperature sensor being at the same temperature
manufacturer-specified operating current for a given
as the system point being monitored. Clearly, if the
transistor. Some manufacturers specify a high-level
temperature sensor is not in good thermal contact
and low-level current for the temperature-sensing
with the part of the system being monitored, then
substrate transistors. The TMP435 uses 6mA for ILOW
there is a delay in the response of the sensor to a
and 120mA for IHIGH. The device allows for different
temperature change in the system. For remote
n-factor values; see the N-Factor Correction Register
temperature sensing applications using a substrate
section.
transistor (or a small, SOT23 transistor) placed close
to the device being monitored, this delay is usually
The ideality factor (n) is a measured characteristic of
not a concern.
a remote temperature sensor diode as compared to
an ideal diode. The ideality factor for the TMP435 is
The local temperature sensor inside the TMP435
trimmed to be 1.008. For transistors whose ideality
monitors the ambient air around the device. The
factor does not match the TMP435, Equation 6 can
thermal
time
constant
for
the
TMP435
is
be used to calculate the temperature error. Note that
approximately two seconds. This constant implies
for
the
equation
to
be
used
correctly,
actual
that if the ambient air changes quickly by 100°C, it
temperature (°C) must be converted to Kelvin (K).
would take the TMP435 about 10 seconds (that is,
five thermal time constants) to settle to within 1°C of
the final value. In most applications, the TMP435
package is in thermal contact with the PCB, as well
Where:
as subjected to forced airflow. The accuracy of the
n = Ideality factor of remote temperature sensor
measured temperature directly depends on how
accurately the PCB and forced airflow temperatures
T(°C) = actual temperature
represent the temperature that the TMP435 is
TERR = Error in TMP435 reading because n ≠
measuring. Additionally, the internal power dissipation
1.008
of the TMP435 can cause the temperature to rise
Degree delta is the same for °C and K
(6)
above the ambient or PCB temperature. The internal
For n = 1.004 and T(°C) = 100°C:
power dissipated as a result of exciting the remote
temperature sensor is negligible because of the small
currents used. For a 5.5V supply and maximum
conversion rate of eight conversions per second, the
TMP435 dissipates 1.82mW (PDIQ = 5.5V × 330mA).
(7)
If both the ALERT/THERM2 and THERM pins are
each sinking 1mA, an additional power of 0.8mW is
If a discrete transistor is used as the remote
dissipated (PDOUT = 1mA × 0.4V + 1mA × 0.4V =
temperature sensor with the TMP435, the best
0.8mW). Total power dissipation is then 2.62mW
accuracy can be achieved by selecting the transistor
(PDIQ + PDOUT) and, with a qJA of 165°C/W, causes
according to the following criteria:
the
junction
temperature
to
rise
approximately
1. Base-emitter voltage > 0.25V at 6mA, at the
0.432°C above the ambient.
highest sensed temperature.
2. Base-emitter voltage < 0.95V at 120mA, at the
lowest sensed temperature.
26
Copyright 2010, Texas Instruments Incorporated
Product Folder Link(s): TMP435
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
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TMP441AIDCNT 功能描述:板上安裝溫度傳感器 Temp Sensor with Auto Beta Comp RoHS:否 制造商:Omron Electronics 輸出類型: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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