参数资料
型号: NVT210CMTR2G
厂商: ON Semiconductor
文件页数: 16/20页
文件大小: 325K
描述: IC TEMP SENSOR DGTL 8-WDFN
标准包装: 3,000
功能: 温度监控系统(传感器)
传感器类型: 内部和外部
感应温度: 0°C ~ 127°C,-64°C ~ 191°C
精确度: ±2.5°C
拓扑: ADC,比较器,多路复用器,寄存器库
输出类型: 2 线串行,I²C?/SMBUS?
输出警报:
输出风扇:
电源电压: 2.8 V ~ 3.6 V
工作温度: -40°C ~ 125°C
安装类型: 表面贴装
封装/外壳: 8-WFDFN
供应商设备封装: 8-WDFN(2x2)
包装: 带卷 (TR)
NVT210
http://onsemi.com
16
Figure 20. Operation of the THERM
 and THERM2
Interrupts
THERM2
 LIMIT
905C
805C
705C
605C
505C
405C
TEMPERATURE
1
2
3
4
THERM
305C
THERM
 LIMIT
THERM2
?SPAN class="pst NVT210DMTR2G_2295433_6"> When the THERM2
 limit is exceeded, the THERM2
signal asserts low.
?SPAN class="pst NVT210DMTR2G_2295433_6"> If the temperature continues to increase and exceeds the
THERM
 limit, the THERM
 output asserts low.
?SPAN class="pst NVT210DMTR2G_2295433_6"> The THERM
 output deasserts (goes high) when the
temperature falls to THERM
 limit minus hysteresis. In
Figure 20, there is no hysteresis value shown.
?SPAN class="pst NVT210DMTR2G_2295433_6"> As the system cools further, and the temperature falls
below the THERM2
 limit, the THERM2
 signal resets.
Again, no hysteresis value is shown for THERM2
.
Both the external and internal temperature measurements
cause THERM
 and THERM2
 to operate as described.
Application Information
Noise Filtering
For temperature sensors operating in noisy environments,
the industry standard practice was to place a capacitor across
the D+ and D pins to help combat the effects of noise.
However, large capacitances affect the accuracy of the
temperature measurement, leading to a recommended
maximum capacitor value of 1,000 pF. Although this
capacitor reduces the noise, it does not eliminate it, making
it difficult to use the sensor in a very noisy environment.
The NVT210 has a major advantage over other devices
when it comes to eliminating the effects of noise on the
external sensor. The series resistance cancellation feature
allows a filter to be constructed between the external
temperature sensor and the part. The effect of any filter
resistance seen in series with the remote sensor is
automatically cancelled from the temperature result.
The construction of a filter allows the NVT210 and the
remote temperature sensor to operate in noisy environments.
Figure 21 shows a low-pass R-C-R filter, where R = 100 W
and C = 1 nF. This filtering reduces both common-mode and
differential noise.
Figure 21. Filter between Remote Sensor and
NVT210 Factors Affecting Diode Accuracy
100 W
100 W
1 nF
D+
D
REMOTE
TEMPERATURE
SENSOR
Remote Sensing Diode
The NVT210 is designed to work with discrete transistors.
Substrate transistors are generally PNP types with the
collector connected to the substrate. Discrete types are either
PNP or NPN transistors connected as diodes (base-shorted
to collector). If an NPN transistor is used, the collector and
base are connected to D+ and the emitter to D. If a PNP
transistor is used, the collector and base are connected to D
and the emitter to D+.
To reduce the error due to variations in discrete transistors,
consider several factors:
?SPAN class="pst NVT210DMTR2G_2295433_6"> The ideality factor, nF, of the transistor is a measure of
the deviation of the thermal diode from ideal behavior.
The NVT210 is trimmed for an nF value of 1.008. The
following equation may be used to calculate the error
introduced at a temperature, T (癈), when using a
transistor whose nF does not equal 1.008. Consult the
processor data sheet for the nF values.
DT = (nF  1.008)/1.008 ?(273.15 Kelvin + T)
To factor this in, the user writes the DT value to the offset
register. It is then automatically added to, or subtracted
from, the temperature measurement.
If a discrete transistor is used with the NVT210, the best
accuracy is obtained by choosing devices according to the
following criteria:
?SPAN class="pst NVT210DMTR2G_2295433_6"> Base-emitter voltage greater than 0.25 V at 6 mA, at the
highest operating temperature
?SPAN class="pst NVT210DMTR2G_2295433_6"> Base-emitter voltage less than 0.95 V at 100 mA, at the
lowest operating temperature
?SPAN class="pst NVT210DMTR2G_2295433_6"> Base resistance less than 100 W
?SPAN class="pst NVT210DMTR2G_2295433_6"> Small variation in h
FE
 (50 to 150) that indicates tight
control of V
BE
 characteristics
Transistors, such as the 2N3904, 2N3906, or equivalents
in SOT23 packages are suitable devices to use.
Thermal Inertia and Self-heating
Accuracy depends on the temperature of the remote
sensing diode and/or the internal temperature sensor being
at the same temperature as that being measured. Many
factors can affect this. Ideally, place the sensor in good
thermal contact with the part of the system being measured.
If it is not, the thermal inertia caused by the sensors mass
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