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參數(shù)資料
| 型號(hào)： | ADT7476ARQZ-REEL7 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | 溫度/濕度傳感器 |
| 英文描述： | DIGITAL TEMP SENSOR-SERIAL, 10BIT(s), 2.50Cel, RECTANGULAR, SURFACE MOUNT |
| 封裝： | ROHS COMPLIANT, MO-137AE, QSOP-24 |
| 文件頁數(shù)： | 14/72頁 |
| 文件大小： | 5219K |
| 代理商： | ADT7476ARQZ-REEL7 |
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ADT7476
Rev. B | Page 21 of 72
value of VBE varies from device to device and individual
calibration is required to null this out, so the technique is
unsuitable for mass production. The technique used in the
ADT7476 is to measure the change in VBE when the device is
operated at two different currents.
This is given by
ΔVBE = KT/q × ln(N)
where:
K is Boltzmann’s constant.
T is the absolute temperature in Kelvin.
q is the charge on the carrier.
ln(N) is the log of the ratio of the two currents (N).
Figure 27 shows the input signal conditioning used to measure
the output of a remote temperature sensor. This figure shows
the external sensor as a substrate transistor, provided for
temperature monitoring on some microprocessors. It can also
be a discrete transistor such as a 2N3904/2N3906.
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 to the D+ input. If
an NPN transistor is used, the emitter is connected to the D–
show how to connect the ADT7476 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.To measure
ΔVBE, the sensor is switched between operating currents of I
and N × I. The resulting waveform is passed through a 65 kHz
low-pass filter to remove noise and to a chopper-stabilized
amplifier that performs the functions of amplification and
rectification of the waveform to produce a dc voltage
proportional to ΔVBE. This voltage is measured by the ADC to
give a temperature output in 10-bit, twos complement format.
To further reduce the effects of noise, digital filtering is
performed by averaging the results of 16 measurement cycles.
A remote temperature measurement takes nominally 38 ms.
The results of remote temperature measurements are stored in
10-bit, twos complement format, as illustrated in Table 10. The
extra resolution for the temperature measurements is held in
the Extended Resolution Register 2 (0x77). This gives temper-
ature readings with a resolution of 0.25°C.
Noise Filtering
For temperature sensors operating in noisy environments, the
previous practice was to place a capacitor across the D+ pin 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 1000 pF.
This capacitor reduces the noise but does not eliminate it, which
makes it difficult to use of the sensor in a very noisy environment.
In most cases, a capacitor is not required because differential
inputs by their very nature have a high immunity to noise.
2N3904
NPN
ADT7476
D+
D–
05382-027
Figure 25. Measuring Temperature Using an NPN Transistor
2N3906
PNP
ADT7476
D+
D–
05382-028
Figure 26. Measuring Temperature Using a PNP Transistor
05
38
2-
0
26
D+
BIAS
DIODE
VDD
TO ADC
VOUT+
VOUT–
REMOTE
SENSING
TRANSISTOR
D–
THERMDA
THERMDC
I
N × I
IBIAS
LOW-PASS FILTER
fC = 65kHz
CPU
Figure 27. Signal Conditioning for Remote Diode Temperature Sensors
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相關(guān)代理商/技術(shù)參數(shù) |
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| ADT7476EBZEVB | 功能描述:BOARD EVALUATION FOR ADT7476 RoHS:是 類別:編程器，開發(fā)系統(tǒng) >> 過時(shí)/停產(chǎn)零件編號(hào) 系列:dBCool® 標(biāo)準(zhǔn)包裝:1 系列:- 傳感器類型:CMOS 成像，彩色（RGB） 傳感范圍:WVGA 接口:I²C 靈敏度:60 fps 電源電壓:5.7 V ~ 6.3 V 嵌入式:否 已供物品:成像器板 已用 IC / 零件:KAC-00401 相關(guān)產(chǎn)品:4H2099-ND - SENSOR IMAGE WVGA COLOR 48-PQFP4H2094-ND - SENSOR IMAGE WVGA MONO 48-PQFP |
| ADT7481 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Dual Channel Temperature Sensor and Over Temperature Alarm |
| ADT7481ARMZ | 功能描述:板上安裝溫度傳感器 2 CH TEMP SNSR/ALARM 2 WIRE SMBUS INTRFCE 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 |
| ADT7481ARMZ-001 | 功能描述:板上安裝溫度傳感器 2 CH TEMP SNSR/ALARM 2 WIRE SMBUS INTRFCE 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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