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| 型号： | ADT7481ARMZ |
| 厂商： | ON Semiconductor |
| 文件页数： | 7/20页 |
| 文件大小： | 237K |
| 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： | 50 |
| 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 ~ 120°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 ~ 120°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： | 管件 |
| 其它名称： | ADT7481ARMZ-ND ADT7481ARMZOS |
ADT7481
http://onsemi.com
7
Theory of Operation
The ADT7481 is a local and dual remote temperature
sensor and over/under temperature alarm. When the
ADT7481 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 remote diode open circuit will cause 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.
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.
This technique requires calibration to null the effect of the
absolute value of V
BE
, which varies from device to device.
The technique used in the ADT7481 measures the change
in V
BE
when the device is operated at two different currents.
Figure 14 shows the input signal conditioning used to
measure the output of a remote temperature sensor. This
figure shows the remote 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 is linked
to the base. To prevent ground noise 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. C1 may optionally be added
as a noise filter with a recommended maximum value of
1,000 pF.
To measure DV
BE
, the operating current through the
sensor is switched among two related currents. The currents
through the temperature diode are switched between I, and
N ?I, giving DV
BE
. The temperature can then be calculated
using the DV
BE
measurement.
The resulting DV
BE
waveforms pass 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 producing a temperature
measurement. 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 local
temperature sensor is performed in the same manner.
Figure 14. Input Signal Conditioning
LOW-PASS FILTER
f
C
= 65 kHz
REMOTE
SENSING
TRANSISTOR
BIAS
DIODE
D+
D
V
DD
I
BIAS
I
N ?I
V
OUT+
V
OUT
To ADC
C1*
*CAPACITOR C1 IS OPTIONAL. IT IS ONLY NECESSARY IN NOISY ENVIRONMENTS. C1 = 1000 pF MAX
Temperature Measurement Results
The results of the local and remote temperature
measurements are stored in the local and remote temperature
value registers and are compared with limits programmed
into the local and remote high and low limit registers.
The local temperature measurement is an 8-bit
measurement with 1癈 resolution. The remote temperature
measurements are 10-bit measurements, with the 8 MSBs
stored in one register and the 2 LSBs stored in another
register. Table 6 is a list of the temperature measurement
registers.
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相关代理商/技术参数 |
参数描述 |
|---|---|
| ADT7481ARMZ-001 | 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 |
| ADT7481ARMZ-1 | 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 |
| ADT7481ARMZ-1R7 | 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 |
| ADT7481ARMZ-1REEL | 制造商:Rochester Electronics LLC 功能描述: 制造商:Analog Devices 功能描述: |
| ADT7481ARMZ-1REEL7 | 制造商:AD 制造商全称:Analog Devices 功能描述:Dual Channel Temperature Sensor and Over Temperature Alarm |
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