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| 型号： | MAX6649YMUA+ |
| 厂商： | MAXIM INTEGRATED PRODUCTS INC |
| 元件分类： | 模拟信号调理 |
| 英文描述： | +145°C Precision SMBus-Compatible Remote/Local Sensors with Overtemperature Alarms |
| 中文描述： | SPECIALTY ANALOG CIRCUIT, DSO8 |
| 封装： | ROHS COMPLIANT, MO-187C-AA, MICRO MAX PACKAGE-8 |
| 文件页数： | 4/22页 |
| 文件大小： | 670K |
| 代理商： | MAX6649YMUA+ |
MAX6646/MAX6647/MAX6649
+145°C Precision SMBus-Compatible Remote/
Local Sensors with Overtemperature Alarms
12
______________________________________________________________________________________
Applications Information
Remote-Diode Selection
The MAX6646/MAX6647/MAX6649 can directly measure
the die temperature of CPUs and other ICs that have
on-board temperature-sensing diodes (see Typical
Operating Circuit), or they can measure the tempera-
ture of a discrete diode-connected transistor.
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 MAX6646/MAX6647/MAX6649
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 different. 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
MAX6646/MAX6647/MAX6649 is 1.008. The following
example uses the MAX6646/MAX6647/MAX6649 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
Ω. 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
Ω, 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.
Discrete Remote Diodes
When the remote-sensing diode is a discrete transistor,
short the collector to the base. Table 10 lists examples
of discrete transistors that are appropriate for use with
the MAX6646/MAX6647/MAX6649.
Avoid violating the A/D input voltage range by using a
small-signal transistor with a relatively high forward volt-
age. The forward voltage at the highest expected tem-
perature must be greater than 0.25V at 10A, and the
forward voltage at the lowest expected temperature
must be less than 0.95V at 100A. Do not use large
power transistors. Ensure that the base resistance is
less than 100
Ω. Tight specifications for forward current
gain (50 < < 150, for example) indicate that the man-
ufacturer has good process controls and that the
devices have consistent VBE characteristics.
3
0 453
1 36
Ω
×
° =°
..
C
90
198 6
0 453
μ
°
=
°
V
C
Ω
.
ΔVR
A
A R
MS
S
=μ
μ =
μ ×
()
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.
AMD and Athlon are trademarks of Advanced Micro Devices, Inc.
MANUFACTURER
MODEL NO.
Central Semiconductor (USA)
CMPT3904
Rohm Semiconductor (USA)
SST3904
Samsung (Korea)
KST3904-TF
Siemens (Germany)
SMBT3904
Zetex (England)
FMMT3904CT-ND
Table 10. Remote-Sensor Transistor
Manufactures
Note: Discrete transistors must be diode connected (base
shorted to collector).
相关PDF资料 |
PDF描述 |
|---|---|
| MAX6649YMUA+T | +145°C Precision SMBus-Compatible Remote/Local Sensors with Overtemperature Alarms |
| MAX6648MUA+ | Precision SMBus-Compatible Remote/Local Temperature Sensors with Overtemperature Alarms |
| 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 |
相关代理商/技术参数 |
参数描述 |
|---|---|
| MAX6649YMUA+ | 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 |
| MAX6649YMUA+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 |
| MAX664C/D | 功能描述:低压差稳压器 - LDO RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX664CJA | 功能描述:低压差稳压器 - LDO RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
| MAX664CPA | 功能描述:低压差稳压器 - LDO RoHS:否 制造商:Texas Instruments 最大输入电压:36 V 输出电压:1.4 V to 20.5 V 回动电压（最大值）:307 mV 输出电流:1 A 负载调节:0.3 % 输出端数量: 输出类型:Fixed 最大工作温度:+ 125 C 安装风格:SMD/SMT 封装 / 箱体:VQFN-20 |
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