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| 型号： | ADT7482ARMZ-REEL |
| 厂商： | ON Semiconductor |
| 文件页数： | 7/20页 |
| 文件大小： | 282K |
| 描述： | IC SENSOR TEMP 2CH ALARM 10MSOP |
| 产品变化通告： | MFG CHG Notification ADI to ON Semi |
| 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： | -40°C ~ 125°C，外部传感器 |
| 精确度： | ±2.5°C（最小值） |
| 拓扑： | ADC，比较器，多路复用器，寄存器库 |
| 输出类型： | SMBus? |
| 输出警报： | 是 |
| 输出风扇： | 是 |
| 电源电压： | 3 V ~ 3.6 V |
| 工作温度： | -40°C ~ 125°C |
| 安装类型： | 表面贴装 |
| 封装/外壳： | 10-TFSOP，10-MSOP（0.118"，3.00mm 宽） |
| 供应商设备封装： | 10-MSOP |
| 包装： | 带卷 (TR) |
ADT7482
http://onsemi.com
7
Theory of Operation
The ADT7482 is a local and 2?remote temperature sensor
and overtemperature/undertemperature alarm. When the
ADT7482 is operating normally, the on-board ADC operates
in a free-running mode. The analog input multiplexer
alternately selects either the on-chip temperature sensor to
measure its local temperature or either of the remote
temperature sensors. The ADC digitizes these signals and the
results are stored in the local, Remote 1, and Remote 2
temperature value registers.
The local and remote measurement results are compared
with the corresponding high, low, and THERM
temperature
limits, stored in on-chip registers. Out-of-limit comparisons
generate flags that are stored in the status register. A result that
exceeds the high temperature limit, the low temperature limit,
or a remote diode open circuit causes the ALERT
output to
assert low. Exceeding THERM
temperature limits causes the
THERM
output to assert low. The ALERT
output can be
reprogrammed as a second THERM
output.
The limit registers can be programmed, and the device
controlled and configured, via the serial SMBus. The
contents of any register can also be read back via the SMBus.
Control and configuration functions consist of switching
the device between normal operation and standby mode,
selecting the temperature measurement scale, masking or
enabling the ALERT
output, switching Pin 8 between
ALERT
and THERM2
, and selecting the conversion rate.
Series Resistance Cancellation
Parasitic resistance to the D+ and D inputs to the
ADT7482, seen in series with the remote diode, is caused by
a variety of factors, including PCB track resistance and track
length. This series resistance appears as a temperature offset
in the remote sensor temperature measurement. This error
typically causes a 0.5癈 offset per ohm of parasitic resistance
in series with the remote diode.
The ADT7482 automatically cancels out the effect of this
series resistance on the temperature reading, providing a more
accurate result, without the need for user characterization of
this resistance. The ADT7482 is designed to automatically
cancel typically up to 1.5 kW of resistance. By using an
advanced temperature measurement method, this is
transparent to the user. This feature allows resistances to be
added to the sensor path to produce a filter, allowing the part
to be used in noisy environments. See the Noise Filtering
section for more details.
Temperature Measurement Method
A simple method of measuring temperature is to exploit
the negative temperature coefficient of a diode, measuring
the base-emitter voltage (V
BE
) of a transistor operated at
constant current. However, this technique requires
calibration to null out the effect of the absolute value of V
BE
,
which varies from device to device.
The technique used in the ADT7482 is to measure the
change in V
BE
when the device is operated at three different
currents. Previous devices have used only two operating
currents. The use of a third current allows automatic
cancellation of resistances in series with the external
temperature sensor.
Figure 15 shows the input signal conditioning used to
measure the output of an external temperature sensor. This
figure shows the external sensor as a substrate transistor, but
it could equally be a discrete transistor. If a discrete
transistor is used, the collector is not grounded and should
be linked to the base. 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.
Capacitor C1 can be added as a noise filter (a recommended
maximum value of 1,000 pF). However, a better option in
noisy environments is to add a filter, as described in the
Noise Filtering section. See the Layout Considerations
section for more information.
To measure DV
BE
, the operating current through the
sensor is switched among three related currents. Shown in
Figure 15, N1 ?I and N2 ?I are different multiples of the
current, I. The currents through the temperature diode are
switched between I and N1 ?I, giving DV
BE1
, and then
between I and N2 ?I, giving DV
BE2
. The temperature can
then be calculated using the two DV
BE
measurements. This
method can also be shown to cancel the effect of any series
resistance on the temperature measurement.
The resulting DV
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
waveform to produce a dc voltage proportional to DV
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
for low conversion rates. At rates of 16, 32, and
64 conversions/second, no digital averaging takes place.
Signal conditioning and measurement of the internal
temperature sensor are performed in the same manner.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADT7482ARMZ-REEL7 | 功能描述:IC SENSOR TEMP 2CH ALARM 10MSOP RoHS:是 类别:集成电路 (IC) >> PMIC - 热管理 系列:- 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 |
| ADT7482ARMZ-RL7 | 功能描述:板上安装温度传感器 2 CH TEMP SNSR/ALARM 2 WIRE SMBUS INTRFCE RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| ADT7483A | 制造商:AD 制造商全称:Analog Devices 功能描述:Dual Channel Temperature Sensor and Over Temperature Alarm |
| ADT7483AARQZ | 功能描述:板上安装温度传感器 2 TEMP DIODE MONITOR 2 WIRE SMBUS INTRFCE RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
| ADT7483AARQZ-R7 | 功能描述:板上安装温度传感器 2 TEMP DIODE MONITOR 2 WIRE SMBUS INTRFCE RoHS:否 制造商:Omron Electronics 输出类型:Digital 配置: 准确性:+/- 1.5 C, +/- 3 C 温度阈值: 数字输出 - 总线接口:2-Wire, I2C, SMBus 电源电压-最大:5.5 V 电源电压-最小:4.5 V 最大工作温度:+ 50 C 最小工作温度:0 C 关闭: 安装风格: 封装 / 箱体: 设备功能:Temperature and Humidity Sensor |
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