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參數(shù)資料
| 型號： | ADT7461AARMZ-R |
| 廠商： | ON Semiconductor |
| 文件頁數(shù)： | 7/19頁 |
| 文件大?。?/td> | 294K |
| 描述： | IC TEMP SENSOR DGTL 2CH 8-MSOP |
| 產(chǎn)品變化通告： | MFG CHG Notification ADI to ON Semi |
| 標準包裝： | 3,000 |
| 功能： | 溫度監(jiān)控系統(tǒng)（傳感器） |
| 傳感器類型： | 內(nèi)部和外部 |
| 感應溫度： | 0°C ~ 127°C，-55°C ~ 150°C |
| 精確度： | ±3°C |
| 拓撲： | ADC，比較器，多路復用器，寄存器庫 |
| 輸出類型： | 2 線 SMBus? |
| 輸出警報： | 是 |
| 輸出風扇： | 是 |
| 電源電壓： | 3 V ~ 5.5 V |
| 工作溫度： | -40°C ~ 120°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 8-TSSOP，8-MSOP（0.118"，3.00mm 寬） |
| 供應商設備封裝： | Micro8? |
| 包裝： | 帶卷 (TR) |
ADT7461A
http://onsemi.com
7
Differences between the ADT7461A and the ADT7461
Although the ADT7461A is pin- and register-compatible
with the ADT7461, there are some specification differences
between the two devices. A summary of these differences is
shown below in Table 6.
Table 6. DIFFERENCES BETWEEN THE ADT7461A
AND THE ADT7461
Specification
ADT7461A
ADT7461
Unit
Supply Voltage
3.0 to 3.6
3.0 to 5.5
V
Maximum Local Sensor
Accuracy
1.0
3.0
癈
Maximum Series
Resistance Cancellation
1.5
3.0
kW
Average Operating
Supply Current
16 Conversions/Sec
Standby Mode
240
5.0
170
5.5
mA
Max Conversion Time
One Shot, Averaging On
One Shot, Averaging Off
52
8.0
114.6
12.56
ms
Remote Sensor Current
Levels
High
Mid
Low
220
82
13.5
96
36
6.0
mA
Theory of Operation
The ADT7461A is a local and remote temperature sensor
and over/under temperature alarm, with the added ability to
automatically cancel the effect of 1.5 kW (typical) of
resistance in series with the temperature monitoring diode.
When the ADT7461A 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 the
remote temperature sensor. The ADC digitizes these signals
and the results are stored in the local and remote temperature
value registers.
The local and remote measurement results are compared
with the corresponding high, low, and THERM
temperature
limits, stored in eight on-chip registers. Out-of-limit
comparisons generate flags that are stored in the status
register. A result that exceeds the high temperature limit or
the low temperature limit causes the ALERT
output to
assert. The ALERT
output also asserts if an external diode
fault is detected. Exceeding the THERM
temperature limits
causes the THERM
output to assert low. The ALERT
output
can be reprogrammed as a second THERM
output.
The limit registers are programmed and the device
controlled and configured via the serial SMBus. The
contents of any register are also read back via the SMBus.
Control and configuration functions consist of switching
the device between normal operation and standby mode,
selecting the temperature measurement range, masking or
enabling the ALERT
output, switching Pin 6 between
ALERT
and THERM2
, and selecting the conversion rate.
Series Resistance Cancellation
Parasitic resistance to the D+ and D inputs to the
ADT7461A, 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 sensors temperature measurement. This
error typically causes a 0.5癈 offset per ohm of parasitic
resistance in series with the remote diode.
The ADT7461A automatically cancels the effect of this
series resistance on the temperature reading, giving a more
accurate result, without the need for user characterization of
this resistance. The ADT7461A is designed to automatically
cancel typically up to 1.5 kW of resistance. By using an
advanced temperature measurement method, this process is
transparent to the user. This feature permits resistances to be
added to the sensor path to produce a filter, allowing the part
to be used in noisy environments. See the section on Noise
Filtering 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 the effect of the absolute value of V
BE
,
which varies from device to device.
The technique used in the ADT7461A measures the
change in V
BE
when the device operates at three different
currents. Previous devices used only two operating currents,
but it is the use of a third current that allows automatic
cancellation of resistances in series with the external
temperature sensor.
Figure 14 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 can equally be a discrete transistor. If a discrete transistor
is used, the collector is not grounded but 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 be added as a noise filter
(a recommended maximum value of 1000 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 on C1.
To measure DV
BE
, the operating current through the
sensor is switched among three related currents. As shown
in Figure 14, 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 is
then calculated using the two DV
BE
measurements. This
method also cancels the effect of any series resistance on the
temperature measurement.
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相關代理商/技術參數(shù) |
參數(shù)描述 |
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| ADT7461AARMZ-REEL | 功能描述:IC SENSOR TEMP DGTL 2CH 8-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱管理 系列:- 標準包裝:1 系列:- 功能:溫度監(jiān)控系統(tǒng)（傳感器） 傳感器類型:內(nèi)部和外部 感應溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠程（最大值） 拓撲:ADC，比較器，寄存器庫 輸出類型:2 線 SMBus? 輸出警報:無 輸出風扇:無 電源電壓:2.7 V ~ 5.5 V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-8 供應商設備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱:296-22675-6 |
| ADT7461AARMZ-REEL7 | 功能描述:IC SENSOR TEMP DGTL 2CH 8-MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱管理 系列:- 標準包裝:1 系列:- 功能:溫度監(jiān)控系統(tǒng)（傳感器） 傳感器類型:內(nèi)部和外部 感應溫度:-40°C ~ 125°C，外部傳感器 精確度:±2.5°C 本地（最大值），±5°C 遠程（最大值） 拓撲:ADC，比較器，寄存器庫 輸出類型:2 線 SMBus? 輸出警報:無 輸出風扇:無 電源電壓:2.7 V ~ 5.5 V 工作溫度:-40°C ~ 125°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-8 供應商設備封裝:SOT-23-8 包裝:Digi-Reel® 其它名稱:296-22675-6 |
| ADT7461AARMZ-RL7 | 功能描述:板上安裝溫度傳感器 1 TMP DIO MON W/SMBUS ITF RoHS:否 制造商:Omron Electronics 輸出類型:Digital 配置: 準確性:+/- 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 關閉: 安裝風格: 封裝 / 箱體: 設備功能:Temperature and Humidity Sensor |
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