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| 型号： | TC665EUN |
| 元件分类： | 运动控制电子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, PDSO10 |
| 封装： | PLASTIC, MSOP-10 |
| 文件页数： | 16/36页 |
| 文件大小： | 695K |
| 代理商： | TC665EUN |
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2002 Microchip Technology Inc.
DS21737A-page 23
TC664/TC665
7.3
Temperature Sensor Design
As discussed in previous sections, the VIN analog input
has a range of 1.62 V to 2.6 V (typical), which repre-
sents a duty cycle range on the VOUT output of 30% to
100%, respectively. The VIN 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:
Temperature Sensing
Circuit.
Figure 7-3 represents a temperature dependent volt-
age divider circuit. Rt is a conventional NTC thermistor,
R1 and R2 are standard resistors. R1 and Rt form a par-
allel resistor combination that will be referred to as
RTEMP (RTEMP = R1 * Rt/ R1 + Rt). As the temperature
increases, the value of Rt decreases and the value of
RTEMP will decrease with it. Accordingly, the voltage at
VIN increases as temperature increases, giving the
desired relationship for the VIN input. The purpose of
R1 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 R1. If less current draw from VDD is desired,
then a larger value thermistor should be chosen. The
voltage at the VIN pin can also be generated by a volt-
age output temperature sensor device. The key is to
get the desired VIN voltage to system (or component)
temperature relationship.
The following equations apply to the circuit in
EQUATION
In order to solve for the values of R1 and R2, the values
for VIN, 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 VIN, you now have two equa-
tions from which the values for R1 and R2 can be found.
Example: The following design goals are desired:
Duty Cycle = 50% (VIN = 1.9 V) with Temperature
(t1) = 30°C
Duty Cycle = 100% (VIN = 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:
Rt = 79428 @ 30°C
Rt = 22593 @ 60°C
Substituting these numbers into the given equations,
we come up with the following numbers for R1 and R2.
R1 = 34.8 k
R2 = 14.7 k
FIGURE 7-4:
How Thermistor Resistance,
VIN, And RTEMP Vary With Temperature.
Figure 7-4 graphs three parameters versus tempera-
ture. They are Rt, R1 in parallel with Rt, and VIN. As
described earlier, you can see that the thermistor has a
logarithmic resistance variation. When put in parallel
with R1, though, the combined resistance becomes
more linear, which is the desired effect. This gives us
the linear looking curve for VIN.
R2
R1
Rt
IDIV
VIN
VDD
Vt1
()
VDD R2
×
RTEMP t1
() R2
+
----------------------------------------
=
Vt2
()
VDD R2
×
RTEMP t2
() R2
+
----------------------------------------
=
0
20000
40000
60000
80000
100000
120000
140000
20
30
40
50
60
70
80
90
100
Temperature (C)
Network
Resistance
(
)
0.000
0.500
1.000
1.500
2.000
2.500
3.000
3.500
4.000
V
IN
(V)
NTC Thermistor
100K @ 25C
VIN Voltage
RTEMP
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC665EUNTR | 功能描述:马达/运动/点火控制器和驱动器 Single RoHS:否 制造商:STMicroelectronics 产品:Stepper Motor Controllers / Drivers 类型:2 Phase Stepper Motor Driver 工作电源电压:8 V to 45 V 电源电流:0.5 mA 工作温度:- 25 C to + 125 C 安装风格:SMD/SMT 封装 / 箱体:HTSSOP-28 封装:Tube |
| TC67 | 功能描述:铝质电解电容器 - 带引线 40uF 350V RoHS:否 制造商:Kemet 引线类型: 电容:220 uF 容差:20 % 电压额定值:25 V 工作温度范围: 端接类型:Radial 外壳直径:8 mm 外壳长度:11 mm 引线间隔:5 mm 产品:General Purpose Electrolytic Capacitors 封装:Bulk |
| TC670 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:Tiny Predictive Fan Failure Detector |
| TC670_03 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:Tiny Predictive Fan Failure Detector |
| TC670_13 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:Tiny Predictive Fan Failure Detector |
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