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參數(shù)資料
| 型號： | MAX6648 |
| 廠商： | Maxim Integrated Products, Inc. |
| 英文描述： | Quadruple 2-Input Positive-NAND Gate 14-CDIP -55 to 125 |
| 中文描述： | 高精度、SMBus兼容、遠(yuǎn)端/本地溫度傳感器，帶有高溫報警 |
| 文件頁數(shù)： | 12/17頁 |
| 文件大?。?/td> | 280K |
| 代理商： | MAX6648 |
M
Precision SMBus-Compatible Remote/Local
Temperature Sensors with Overtemperature Alarms
12
______________________________________________________________________________________
Effect of Ideality Factor
The accuracy of the remote temperature measurements
depends on the ideality factor (n) of the remote
“
diode
”
(actually a transistor). The MAX6648/MAX6692 are opti-
mized for n = 1.008, which is the typical value for the
Intel
Pentium
III and the AMD Athlon MP model 6. If a
sense transistor with a different ideality factor is used,
the output data is different. Fortunately, the difference
is predictable.
Assume a remote-diode sensor designed for a nominal
ideality factor n
NOMINAL
is used to measure the tem-
perature of a diode with a different ideality factor n
1
.
The measured temperature T
M
can be corrected using:
where temperature is measured in Kelvin.
As mentioned above, the nominal ideality factor of the
MAX6648/MAX6692 is 1.008. As an example, assume
you want to use the MAX6648/MAX6692 with a CPU
that has an ideality factor of 1.002.
If the diode has no series resistance, the measured
data is related to the real temperature as follows:
For a real temperature of +85
°
C (358.15 K), the mea-
sured temperature is +82.91
°
C (356.02 K), which is an
error of -2.13
°
C.
Effect of Series Resistance
Series resistance in a sense diode contributes addition-
al errors. For nominal diode currents of 10μA and
100μA, change in the measured voltage is:
Since 1
°
C corresponds to 198.6μV, series resistance
contributes a temperature offset of:
μ
V
Assume that the diode being measured has a series
resistance of 3
. The series resistance contributes an
offset of:
The effects of the ideality factor and series resistance
are additive. If the diode has an ideality factor of 1.002
and series resistance of 3
, the total offset can be cal-
culated by adding error due to series resistance with
error due to ideality factor:
1.36
°
C - 2.13
°
C = -0.77
°
C
for a diode temperature of +85
°
C.
In this example, the effect of the series resistance and
the ideality factor partially cancel each other.
For best accuracy, the discrete transistor should be a
small-signal device with its collector and base connect-
ed together. Table 9 lists examples of discrete transis-
tors that are appropriate for use with the MAX6648/
MAX6692.
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, the 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 specifications for forward current gain (50 <
<150, for example) indicate that the manufacturer has
good process controls and that the devices have con-
sistent V
BE
characteristics.
ADC Noise Filtering
The integrating ADC used has good noise rejection for
low-frequency signals such as 60Hz/120Hz power-sup-
ply hum. In noisy environments, high-frequency noise
reduction is needed for high-accuracy remote mea-
3
0 453
.
1 36
.
×
°
=
°
C
C
90
198 6
0 453
.
μ
°
=
°
V
C
C
.
V
R
A
A
μ ×
90
M
S
S
=
μ
μ
=
(
)
100
10
T
T
n
n
T
T
ACTUAL
M
NOMINAL
1
M
M
=
=
.
.
1 00599
)
1 008
1 002
T
T
n
n
M
ACTUAL
NOMINAL
=
1
Intel and Pentium are registered trademarks of Intel Corp.
MANUFACTURER
Central Semiconductor (USA)
Rohm Semiconductor (USA)
Samsung (Korea)
Siemens (Germany)
MODEL NO.
CMPT3904
SST3904
KST3904-TF
SMBT3904
Table 9. Remote-Sensor Transistor
Manufacturers
Note:
Transistors must be diode connected (base shorted to
collector).
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| MAX6648-MAX6692 | 10 AMP MINIATURE POWER RELAY |
| MAX6692MSA | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6692MUA | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6692 | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6648MUA | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| MAX6648MUA | 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 |
| MAX6648MUA+ | 功能描述:板上安裝溫度傳感器 145C SMBus-Comp Remote/Local 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 |
| MAX6648MUA+T | 功能描述:板上安裝溫度傳感器 145C SMBus-Comp Remote/Local 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 |
| MAX6648MUA-T | 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 |
| MAX6648YMUA+ | 功能描述:板上安裝溫度傳感器 145C SMBus-Comp Remote/Local 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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