- 您現(xiàn)在的位置：買賣IC網(wǎng) > PDF目錄384955 > TC664 (Microchip Technology Inc.) SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection PDF資料下載
參數(shù)資料
| 型號： | TC664 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
| 中文描述： | ⑩的SMBus PWM風(fēng)扇與風(fēng)扇轉(zhuǎn)速控制器故障檢測 |
| 文件頁數(shù)： | 23/36頁 |
| 文件大小： | 695K |
| 代理商： | TC664 |
第1頁第2頁第3頁第4頁第5頁第6頁第7頁第8頁第9頁第10頁第11頁第12頁第13頁第14頁第15頁第16頁第17頁第18頁第19頁第20頁第21頁第22頁當(dāng)前第23頁第24頁第25頁第26頁第27頁第28頁第29頁第30頁第31頁第32頁第33頁第34頁第35頁第36頁
2002 Microchip Technology Inc.
DS21737A-page 23
TC664/TC665
7.3
Temperature Sensor Design
As discussed in previous sections, the V
IN
analog input
has a range of 1.62 V to 2.6 V (typical), which repre-
sents a duty cycle range on the V
OUT
output of 30% to
100%, respectively. The V
IN
voltages can be thought of
as representing temperatures. The 1.62 V level is the
low temperature at which the system only requires 30%
fan speed for proper cooling. The 2.6 V level is the high
temperature, for which the system needs maximum
cooling capability, so the fan needs to be at 100%
speed.
One of the simplest ways of sensing temperature over
a given range is to use a thermistor. By using an NTC
thermistor as shown in Figure 7-3, a temperature vari-
ant voltage can be created.
FIGURE 7-3:
Circuit.
Temperature Sensing
Figure 7-3 represents a temperature dependent volt-
age divider circuit. R
t
is a conventional NTC thermistor,
R
1
and R
2
are standard resistors. R
1
and R
t
form a par-
allel resistor combination that will be referred to as
R
TEMP
(R
TEMP
= R
1
* R
t
/ R
1
+ R
t
). As the temperature
increases, the value of R
t
decreases and the value of
R
TEMP
will decrease with it. Accordingly, the voltage at
V
IN
increases as temperature increases, giving the
desired relationship for the V
IN
input. The purpose of
R
1
is to help linearize the response of the sensing net-
work. Figure 7-4 shows an example of this.
There are many values that can be chosen for the NTC
thermistor. There are also thermistors that have a linear
resistance, instead of logarithmic, which can help to
eliminate R
1
. If less current draw from V
DD
is desired,
then a larger value thermistor should be chosen. The
voltage at the V
IN
pin can also be generated by a volt-
age output temperature sensor device. The key is to
get the desired V
IN
voltage to system (or component)
temperature relationship.
The following equations apply to the circuit in
Figure 7-3.
EQUATION
In order to solve for the values of R
1
and R
2
, the values
for V
IN,
and the temperatures at which they are to
occur, need to be selected. The variables, t1 and t2,
represent the selected temperatures. The value of the
thermistor at these two temperatures can be found in
the thermistor data sheet. With the values for the ther-
mistor and the values for V
IN
, you now have two equa-
tions from which the values for R
1
and R
2
can be found.
Example:
The following design goals are desired:
Duty Cycle = 50% (V
IN
= 1.9 V) with Temperature
(t1) = 30°C
Duty Cycle = 100% (V
IN
= 2.6 V) with Tempera-
ture (t2) = 60°C
Using a 100 k
thermistor (25°C value), we look up the
thermistor values at the desired temperatures:
R
t
= 79428
@ 30°C
R
t
= 22593
@ 60°C
Substituting these numbers into the given equations,
we come up with the following numbers for R
1
and R
2
.
R
1
= 34.8 k
R
2
= 14.7 k
FIGURE 7-4:
V
IN
, And R
TEMP
Vary With Temperature.
Figure 7-4 graphs three parameters versus tempera-
ture. They are R
t
, R
1
in parallel with R
t
, and V
IN
. As
described earlier, you can see that the thermistor has a
logarithmic resistance variation. When put in parallel
with R
1
, though, the combined resistance becomes
more linear, which is the desired effect. This gives us
the linear looking curve for V
IN
.
How Thermistor Resistance,
R
2
R
1
R
t
I
DIV
V
IN
V
DD
V t1
)
V
R
×
R
TEMP
t1
R
2
+
---------------------------------------
=
V t2
)
V
R
×
R
TEMP
t2
R
2
+
---------------------------------------
=
0
20000
40000
60000
80000
100000
120000
140000
20
30
40
50
60
70
80
90
100
Temperature (oC)
N
:
)
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
V
I
NTC Thermistor
100K @ 25oC
V
IN
Voltage
R
TEMP
相關(guān)PDF資料 |
PDF描述 |
|---|---|
| TC665 | SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
| TC670ECH | Tiny Predictive Fan Failure Detector |
| TC7400BP | TC7400BP |
| TC74AC00F | Quad 2-Input NAND Gate(四2輸入與非門) |
| TC74AC00FN | Quad 2-Input NAND Gate(四2輸入與非門) |
相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| TC664_36 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:SMBusa?￠ PWM Fan Speed Controllers With Fan Fault Detection |
| TC664EUN | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Single RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| TC664EUNTR | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Single RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| TC665 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
| TC665EUN | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 Single RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
發(fā)布緊急采購，3分鐘左右您將得到回復(fù)。