參數(shù)資料
型號: MAX6645BAFAUB+T
廠商: MAXIM INTEGRATED PRODUCTS INC
元件分類: 模擬信號調(diào)理
英文描述: Automatic PWM Fan-Speed Controllers with Overtemperature Output
中文描述: SPECIALTY ANALOG CIRCUIT, PDSO10
封裝: 3 X 3 MM, ROHS COMPLIANT, MO-187CBA, MICRO, SOP-10
文件頁數(shù): 18/19頁
文件大?。?/td> 630K
代理商: MAX6645BAFAUB+T
MAX6643/MAX6644/MAX6645
Applications Information
Figures 3–6 show various configurations.
Remote-Diode Considerations
When using an external thermal diode, temperature
accuracy depends upon having a good-quality, diode-
connected, small-signal transistor. Accuracy has been
experimentally verified for a variety of discrete small-
signal transistors, some of which are listed in Table 5.
The MAX6643/MAX6644/MAX6645 can also directly
measure the die temperature of CPUs and other ICs
with on-board temperature-sensing diodes.
The transistor must be a small-signal type with a rela-
tively high forward voltage. This ensures that the input
voltage is within the ADC input voltage range. The for-
ward voltage must be greater than 0.25V at 10A at the
highest expected temperature. The forward voltage
must be less than 0.95V at 100A at the lowest expect-
ed temperature. The base resistance has to be less
than 100
. Tight specification of forward-current gain
(+50 to +150, for example) indicates that the manufac-
turer has good process control and that the devices
have consistent characteristics.
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 MAX6643/MAX6644/MAX6645
are optimized for n = 1.01, which is typical of many dis-
crete 2N3904 and 2N3906 transistors. It is also near the
ideality factors of many widely available CPUs, GPUs, and
FPGAs. However, any time a sense transistor with a differ-
ent ideality factor is used, the output data is different.
Fortunately, the difference is predictable. Assume a
remote-diode sensor designed for a nominal ideality fac-
tor nNOMINAL is used to measure the temperature 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
MAX6643/MAX6644/MAX6645 is 1.01. As an example,
assume the MAX6643/MAX6644/MAX6645 are config-
ured with a CPU that has an ideality factor of 1.008. If
the diode has no series resistance, the measured data
is related to the real temperature as follows:
For a real temperature of +60°C (333.15K), the mea-
sured temperature is 59.33°C (332.49K), which is an
error of -0.66°C.
TT
n
T
1.01
1.008
T
ACTUAL
M
NOMINAL
1
MM
=
=
=
()
.
1 00198
TT
n
M
ACTUAL
1
NOMINAL
=
Automatic PWM Fan-Speed Controllers with
Overtemperature Output
8
_______________________________________________________________________________________
MANUFACTURER
MODEL NO.
Central Semiconductor (USA)
CMPT3906
Rohm Semiconductor (USA)
SST3906
Samsung (Korea)
KST3906-TF
Siemens (Germany)
SMBT3906
Table 5. Remote-Sensor Transistor
Manufacturers
OT2
OT1
TOVERT (°C)
L SUFFIX
00
60
0
High-Z
65
01
70
High-Z
0
75
High-Z
80
High-Z
1
85
10
90
1
High-Z
95
11
100
Table 4. Setting the Overtemperature
Thresholds (TOVERT) (MAX6643 and MAX6644)
Table 3. Configuring the FAN_IN_ Inputs with TACHSET
VDD
GND
UNCONNECTED
TACHSET
FAN_IN1
FAN_IN2
FAN_IN1
FAN_IN2
FAN_IN1
FAN_IN2
MAX6643
Tachometer
Do not connect
to GND
Do not connect
to GND
Disables fan-
failure detection
Disables fan-
failure detection
MAX6644
Tachometer
Current sense
Locked rotor
MAX6645
Tachometer
Current sense
Locked rotor
High-Z = high impedance
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參數(shù)描述
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MAX6646MUA-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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