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參數(shù)資料
| 型號(hào)： | MAX6681 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Quadruple 2-Line To 1-Line Data Selector/Multiplexer With 3-State Outputs 16-CFP -55 to 125 |
| 中文描述： | ±1°C、具有失效保護(hù)的遠(yuǎn)端/本地溫度傳感器，帶有SMBus接口 |
| 文件頁(yè)數(shù)： | 7/17頁(yè) |
| 文件大?。?/td> | 194K |
| 代理商： | MAX6681 |
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age and computes the temperature based on this volt-
age. If the remote channel is not used, connect DXP to
DXN.
Do not leave DXP and DXN unconnected.
When a conversion is initiated, both channels are con-
verted whether or not they are used. The DXN input is
biased at one V
BE
above ground by an internal diode
to set up the ADC inputs for a differential measurement.
Resistance in series with the remote diode causes
about 1/2
°
C error per ohm.
A/D Conversion Sequence
A conversion sequence consists of a local temperature
measurement and a remote temperature measurement.
Each time a conversion begins, whether initiated auto-
matically in the free-running autoconvert mode
(RUN/STOP = 0) or by writing a One-Shot command,
both channels are converted, and the results of both
measurements are available after the end of conver-
sion. A BUSY status bit in the Status register shows that
the device is actually performing a new conversion. The
results of the previous conversion sequence are still
available when the ADC is busy.
Remote-Diode Selection
The MAX6680/MAX6681 can directly measure the die
temperature of CPUs and other ICs that have on-board
temperature-sensing diodes (see the
Typical Operating
Circuit
) or they can measure the temperature of a dis-
crete diode-connected transistor. The type of remote
diode used is set by bit 5 of the Configuration Byte. If
bit 5 is set to zero, the remote sensor is a diode-con-
nected transistor, and if bit 5 is set to 1, the remote sen-
sor is a substrate or common-collector PNP transistor.
For best accuracy, the discrete transistor should be a
small-signal device with its collector and base connect-
ed together. Accuracy has been experimentally verified
for all of the devices listed in Table 1.
The transistor must be a small-signal type with a rela-
tively high forward voltage; otherwise, the A/D input
voltage range can be violated. The forward voltage at
the highest expected temperature must be greater than
0.25V at 10μA, and at the lowest expected tempera-
ture, forward voltage must be less than 0.95V at 100μA.
Large power transistors must not be used. Also, ensure
that the base resistance is less than 100
. Tight speci-
fications for forward-current gain (50 <
< 150, for
example) indicate that the manufacturer has good
process controls and that the devices have consistent
V
BE
characteristics.
Thermal Mass and Self-Heating
When sensing local temperature, these temperature
sensors are intended to measure the temperature of the
PC board to which they are soldered. The leads pro-
vide a good thermal path between the PC board traces
and the die. Thermal conductivity between the die and
the ambient air is poor by comparison, making air-tem-
perature measurements impractical. Because the ther-
mal mass of the PC board is far greater than that of the
MAX6680/MAX6681, the device follows temperature
changes on the PC board with little or no perceivable
delay.
When measuring the temperature of a CPU or other IC
with an on-chip sense junction, thermal mass has virtu-
ally no effect; the measured temperature of the junction
tracks the actual temperature within a conversion cycle.
When measuring temperature with discrete remote sen-
sors, smaller packages (e.g., a SOT23) yield the best
thermal response times. Take care to account for ther-
mal gradients between the heat source and the sensor,
and ensure that stray air currents across the sensor
package do not interfere with measurement accuracy.
Self-heating does not significantly affect measurement
accuracy. Remote-sensor self-heating due to the diode
current source is negligible. For the local diode, the
worst-case error occurs when autoconverting at the
fastest rate and simultaneously sinking maximum cur-
rent at the
ALERT
output. For example, with V
CC
=
5.0V, an 8Hz conversion rate, and
ALERT
sinking 1mA,
the typical power dissipation is V
CC
550μA + 0.4V
1mA, which equals 2.75mW;
θ
J-A
for the 16-pin QSOP
package is about +120
°
C/W, so assuming no copper
PC board heat sinking, the resulting temperature rise is:
Even under these engineered circumstances, it is diffi-
cult to introduce significant self-heating errors.
ADC Noise Filtering
The integrating ADC used has good noise rejection for
low-frequency signals such as 60Hz/120Hz power-sup-
T
mW
C W
°
/
C
=
×
=
°
2 75
.
120
0 330
.
M
±1°C Fail-Safe Remote/Local Temperature
Sensors with SMBus Interface
_______________________________________________________________________________________
7
MANUFACTURER
Central Semiconductor (USA)
On Semiconductor (USA)
Rohm Semiconductor (USA)
Samsung (Korea)
Siemens (Germany)
Zetex (England)
MODEL NO.
CMPT3904
2N3904, 2N3906
SST3904
KST3904-TF
SMBT3904
FMMT3904CT-ND
Table 1. Remote-Sensor Transistor
Manufacturers
Note:
Transistors must be diode connected (base shorted to
collector).
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX6681EVKIT | 功能描述:板上安裝溫度傳感器 Evaluation System/Evaluation Kit for the MAX6681 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 |
| MAX6681EVSYS | 功能描述:板上安裝溫度傳感器 1 C Fail-Safe Remote/Local Temperature Sensors with SMBus Interface 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 |
| MAX6681MEE | 功能描述:板上安裝溫度傳感器 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 |
| MAX6681MEE+ | 功能描述:板上安裝溫度傳感器 Fail-Safe Temperature Sensor 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 |
| MAX6681MEE+T | 功能描述:板上安裝溫度傳感器 Fail-Safe Temperature Sensor 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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