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参数资料
| 型号： | MAX6648MUA+ |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 温度/湿度传感器 |
| 英文描述： | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| 中文描述： | DIGITAL TEMP SENSOR-SERIAL, 10BIT(s), 0.80Cel, SQUARE, SURFACE MOUNT |
| 封装： | LEAD FREE, MO-187CAA, USOP-8 |
| 文件页数： | 4/19页 |
| 文件大小： | 295K |
| 代理商： | MAX6648MUA+ |
MAX6648/MAX6692
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 (not the
MAX6648Y/MAX6692Y) are optimized 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 differ-
ent. Fortunately, the difference is predictable.
Assume a remote-diode sensor designed for a nominal
ideality factor nNOMINAL is used to measure the tem-
perature of a diode with a different ideality factor n1.
The measured temperature TM 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 10A and
100A, change in the measured voltage is:
Since 1°C corresponds to 198.6V, series resistance
contributes a temperature offset of:
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 10A, and at the lowest expected tempera-
ture, the forward voltage must be less than 0.95V at
100A. 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 VBE 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
90
198 6
0 453
°
=
°
V
C
.
VR
A
A R
MS
S
=
=
×
()
100
10
90
TT
n
TT
ACTUAL
M
NOMINAL
MM
=
=
=
.
(.
)
1
1 008
1 002
1 00599
TT
n
M
ACTUAL
NOMINAL
=
1
Intel and Pentium are registered trademarks of Intel Corp.
MANUFACTURER
MODEL NO.
Central Semiconductor (USA)
CMPT3904
Rohm Semiconductor (USA)
SST3904
Samsung (Korea)
KST3904-TF
Siemens (Germany)
SMBT3904
Table 9. Remote-Sensor Transistor
Manufacturers
Note: Transistors must be diode connected (base shorted to
collector).
相关PDF资料 |
PDF描述 |
|---|---|
| MAX6648YMUA+ | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6692YMSA+ | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6692YMSA+T | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6692YMUA+ | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| MAX6692YMUA+T | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX6648MUA+ | 功能描述:板上安装温度传感器 145C SMBus-Comp Remote/Local Sensor 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 |
| MAX6648MUA+T | 功能描述:板上安装温度传感器 145C SMBus-Comp Remote/Local Sensor 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 |
| MAX6648MUA-T | 功能描述:板上安装温度传感器 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 |
| MAX6648YMUA+ | 功能描述:板上安装温度传感器 145C SMBus-Comp Remote/Local Sensor 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 |
| MAX6648YMUA+T | 功能描述:板上安装温度传感器 145C SMBus-Comp Remote/Local Sensor 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 |
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