参数资料
| 型号： | ADT7473ZEVB |
| 厂商： | ON Semiconductor |
| 文件页数： | 16/73页 |
| 文件大小： | 0K |
| 描述： | BOARD EVALUATION FOR ADT7473 |
| 产品变化通告： | MFG CHG Notification ADI to ON Semi |
| 标准包装： | 1 |
| 系列： | dBCool® |
| 类型： | 温度传感器 |
| 适用于相关产品： | ADT7473 |
| 所含物品： | 评估板 |
| 其它名称： | EVAL-ADT7473EBZ EVAL-ADT7473EBZ-ND |
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ADT7473
I
N2 ? I
N1 ? I
I BIAS
V DD
D+
V OUT+
REMOTE
SENSING
TRANSISTOR
D ?
LOW-PASS FILTER
f C = 65 kHz
Figure 24. Signal Conditioning for Remote Diode Temperature Sensors
To ADC
V OUT ?
If a discrete transistor is used, the collector is not grounded
and should be linked to the base. If a PNP transistor is used,
the base is connected to the D– input and the emitter is
connected to the D+ input. If an NPN transistor is used, the
emitter is connected to the D– input and the base is
connected to the D+ input. Figure 25 and Figure 26 show
how to connect the ADT7473/ADT7473 ? 1 to an NPN or
PNP transistor for temperature measurement. To prevent
ground noise from interfering with the measurement, the
more negative terminal of the sensor is not referenced to
ground, but is biased above ground by an internal diode at
the D– input.
ADT7473/
ADT7473 ? 1
waveform to produce a dc voltage proportional to D V BE .
The ADC digitizes this voltage, and a temperature
measurement is produced. To reduce the effects of noise,
digital filtering is performed by averaging the results of 16
measurement cycles.
The results of remote temperature measurements are
stored in 10-bit, twos complement format, as listed in
Table 10. The extra resolution for the temperature
measurements is held in the Extended Resolution Register 2
(0x77). This gives temperature readings with a resolution of
0.25 ? C.
Noise Filtering
For temperature sensors operating in noisy environments,
previous practice was to place a capacitor across the D+ pin
2N3904
NPN
D+
D ?
and the D ? pin 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. This capacitor reduces the
Figure 25. Measuring Temperature by Using an NPN
Transistor
noise, but does not eliminate it, making use of the sensor
difficult in a very noisy environment.
The ADT7473/ADT7473 ? 1 has a major advantage over
2N3906
PNP
ADT7473/
ADT7473 ? 1
D+
D ?
other devices for eliminating the effects of noise on the
external sensor. Using the series resistance cancellation
feature, a filter can 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 canceled from the temperature result.
1 nF
Figure 26. Measuring Temperature by Using a PNP
Transistor
To measure D V BE , the operating current through the
sensor is switched among three related currents. N1 ? I and
N2 ? I are different multiples of the current I, as shown in
Figure 24. The currents through the temperature diode are
switched between I and N1 ? I, giving D V BE1 , and then
between I and N2 ? I, giving D V BE2 . The temperature can
then be calculated using the two D V BE measurements. This
method can also cancel the effect of any series resistance on
the temperature measurement.
The resulting D V BE waveforms are passed through a
65 kHz low-pass filter to remove noise and then to a
chopper-stabilized amplifier. This amplifies and rectifies the
The construction of a filter allows the ADT7473/
ADT7473 ? 1 and the remote temperature sensor to operate
in noisy environments. Figure 27 shows a low-pass R-C
filter with the following values:
R + 100 W , C + 1 nF (eq. 1)
This filtering reduces both common-mode noise and
differential noise.
100 W
D+
REMOTE
TEMPERATURE 100 W
SENSOR D ?
Figure 27. Filter Between Remote Sensor and
ADT7473/ADT7473 ? 1
http://onsemi.com
16
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| ADT7475ARQZ-REEL7 | 功能描述:IC REMOTE THERMAL CTRLR 16QSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热管理 系列:dBCool® 标准包装:1 系列:- 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:-40°C ~ 125°C，外部传感器 精确度:±2.5°C 本地（最大值），±5°C 远程（最大值） 拓扑:ADC，比较器，寄存器库 输出类型:2 线 SMBus? 输出警报:无 输出风扇:无 电源电压:2.7 V ~ 5.5 V 工作温度:-40°C ~ 125°C 安装类型:表面贴装 封装/外壳:SOT-23-8 供应商设备封装:SOT-23-8 包装:Digi-Reel® 其它名称:296-22675-6 |
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