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參數資料
| 型號： | ADT7481ARMZ-1RL |
| 廠商： | ON Semiconductor |
| 文件頁數： | 17/20頁 |
| 文件大小： | 237K |
| 描述： | IC SENSOR TEMP 2CH ALARM 10MSOP |
| 產品變化通告： | MFG CHG Notification ADI to ON Semi |
| 標準包裝： | 3,000 |
| 功能： | 溫度監控系統（傳感器） |
| 傳感器類型： | 內部和外部 |
| 感應溫度： | -40°C ~ 120°C，外部傳感器 |
| 精確度： | ±2.5°C（最小值） |
| 拓撲： | ADC，比較器，多路復用器，寄存器庫 |
| 輸出類型： | SMBus? |
| 輸出警報： | 是 |
| 輸出風扇： | 是 |
| 電源電壓： | 3 V ~ 3.6 V |
| 工作溫度： | -40°C ~ 120°C |
| 安裝類型： | 表面貼裝 |
| 封裝/外殼： | 10-TFSOP，10-MSOP（0.118"，3.00mm 寬） |
| 供應商設備封裝： | 10-MSOP |
| 包裝： | 帶卷 (TR) |
| 其它名稱： | ADT7481ARMZ-1REEL ADT7481ARMZ-1REEL-ND |
ADT7481
http://onsemi.com
17
Pin 8 on the ADT7481 can be configured as either an
ALERT
output or as an additional THERM
output.
THERM2
will assert low when the temperature exceeds the
programmed local and/or remote high temperature limits. It
is reset in the same manner as THERM
, and it is not
maskable. The programmed hysteresis value also applies to
THERM2
.
Figure 20 shows how THERM
and THERM2
might
operate together to implement two methods of cooling the
system. In this example, the THERM2
limits are set lower
than the THERM
limits. The THERM2
output could be used
to turn on a fan. If the temperature continues to rise and
exceeds the THERM
limits, the THERM
output could
provide additional cooling by throttling the CPU.
Figure 20. Operation of the THERM
and THERM2
Interrupts
THERM2
LIMIT
905C
805C
705C
605C
505C
405C
TEMPERATURE
1
2
3
4
THERM
305C
THERM
LIMIT
THERM2
When the THERM2
limit is exceeded, the THERM2
signal asserts low.
" If the temperature continues to increase and exceeds the
THERM
limit, the THERM
output asserts low.
" , there is no hysteresis value shown.
" As the system cools further, and the temperature falls
below the THERM2
limit, the THERM2
signal resets.
Again, no hysteresis value is shown for THERM2
.
The temperature measurement could be either the local or
the remote temperature measurement.
Applications Information
Noise Filtering
For temperature sensors operating in noisy environments,
previous practice was to place a capacitor across the D+ and
D pins 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.
Factors Affecting Diode Accuracy
Remote Sensing Diode
The ADT7481 is designed to work with substrate
transistors built into processors or with discrete transistors.
Substrate transistors will generally be PNP types with the
collector connected to the substrate. Discrete types can be
either a PNP or an NPN transistor connected as a diode (base
shorted to collector). If an NPN transistor is used, the
collector and base are connected to D+ and the emitter to D.
If a PNP transistor is used, the collector and base are
connected to D and the emitter to D+.
To reduce the error due to variations in both substrate and
discrete transistors, a number of factors should be taken into
consideration:
" The ideality factor, n
f
, of the transistor is a measure of
the deviation of the thermal diode from ideal behavior.
The ADT7481 is trimmed for an n
f
value of 1.008. Use
the following equation to calculate the error introduced
at a temperature, T (癈), when using a transistor where
n
f
does not equal 1.008. Consult the processor data
sheet for the n
f
values.
(eq. 2)
DT +
n
f
* 1.008
1.008
273.15 Kelvin ) T
To factor this in, the user can write the DT value to the
offset register. It will then automatically be added to, or
subtracted from, the temperature measurement by the
ADT7481.
" Some CPU manufacturers specify the high and low
current levels of the substrate transistors. The high
current level of the ADT7481, I
HIGH
, is 233mA. The
low level current, I
LOW
, is 14mA. If the ADT7481
current levels do not match the current levels specified
by the CPU manufacturer, it may become necessary to
remove an offset. The CPU data sheet will advise
whether this offset needs to be removed and how to
calculate it. This offset may be programmed to the
offset register. It is important to note that if more than
one offset must be considered, the algebraic sum of
these offsets must be programmed to the offset register.
If a discrete transistor is being used with the ADT7481,
the best accuracy is obtained by choosing devices according
to the following criteria:
" Base-emitter voltage greater than 0.25 V at 6 mA, at the
highest operating temperature.
" Base-emitter voltage less than 0.95 V at 100 mA, at the
lowest operating temperature.
" Base resistance less than 100 W.
" Small variation in h
FE
(say 50 to 150) that indicates
tight control of V
BE
characteristics.
Transistors, such as 2N3904, 2N3906, or equivalents in
SOT23 packages, are suitable devices to use.
Thermal Inertia and Self-heating
Accuracy depends on the temperature of the remote
sensing diode and/or the local temperature sensor being at
the same temperature as that being measured. A number of
factors can affect this. Ideally, the sensor should be in good
thermal contact with the part of the system being measured;
otherwise, the thermal inertia caused by the sensors mass
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相關代理商/技術參數 |
參數描述 |
|---|---|
| ADT7481ARMZ-R7 | 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: 準確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數字輸出 - 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 |
| ADT7481ARMZ-REEL | 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: 準確性:+/- 1.5 C, +/- 3 C 溫度閾值: 數字輸出 - 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 |
| ADT7481ARMZ-REEL7 | 功能描述:IC SENSOR TEMP 2CH ALARM 10MSOP RoHS:是 類別:集成電路 (IC) >> PMIC - 熱管理 系列:- 標準包裝:1 系列:- 功能:溫度監控系統（傳感器） 傳感器類型:內部和外部 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 |
| ADT7481EBZEVB | 功能描述:EVALUATION BOARD ADT7481 制造商:on semiconductor 系列:* 零件狀態:在售 標準包裝:1 |
| ADT7482 | 制造商:AD 制造商全稱:Analog Devices 功能描述:Dual Channel Temperature Sensor and Overtemperature Alarm |
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