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参数资料
| 型号： | TC642DEMO |
| 厂商： | Microchip Technology Inc. |
| 英文描述： | PWM Fan Speed Controller with FanSense⑩ Technology |
| 中文描述： | 与FanSense PWM风扇速度控制器⑩技术 |
| 文件页数： | 10/28页 |
| 文件大小： | 485K |
| 代理商： | TC642DEMO |
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TC642
DS21444C-page 10
2002 Microchip Technology Inc.
FIGURE 5-2:
Circuit.
Temperature Sensing
Generally, the thermistor shown in Figure 5-2 is a non-
linear device with a negative temperature coefficient
(also called an NTC thermistor). In Figure 5-2, R
1
is
used to linearize the thermistor temperature response,
while R
2
is used to produce a positive temperature
coefficient at the V
IN
node. As an added benefit, this
configuration produces an output voltage delta of 1.4V,
which is well within the range of the V
C(SPAN)
specification of the TC642. A 100 k
NTC thermistor is
selected for this application in order to keep I
DIV
at a
minimum.
For the voltage range at V
IN
to be equal to 1.25V to
2.65V, the temperature range of this configuration is
0°C to 50°C. If a different temperature range is required
from this circuit, R
1
should be chosen to equal the
resistance value of the thermistor at the center of this
new temperature range. With this change, R
2
is
adjusted according to the formulas below. It is
suggested that a maximum temperature range of 50°C
be used with this circuit due to thermistor linearity
limitations.
The following two equations permit solving for the two
unknown variables, R
1
and R
2
. More information
regarding thermistors can be found in AN679, “Temper-
ature Sensing Technologies”, and AN685, “Thermistors
in Single Supply Temperature Sensing Circuits”, which
can be downloaded from Microchip’s web site at:
www.microchip.com.
EQUATION
5.2
Minimum Fan Speed
A voltage divider on V
MIN
sets the minimum PWM duty
cycle and, thus, the minimum fan speed. As with the
V
IN
input, 1.25V to 2.65V typically corresponds to 0%
to 100% duty cycle. Assuming that fan speed is linearly
related to duty cycle, the minimum speed voltage is
given by the equation:
EQUATION
For example, if 2500 RPM equates to 100% fan speed,
and a minimum speed of 1000 RPM is desired, then
the V
MIN
voltage is:
EQUATION
The V
MIN
voltage may be set using a simple resistor
divider, as shown in Figure 5-3. Per Section 1.0,
“Electrical Characteristics”, the leakage current at the
V
MIN
pin is no more than 1 μA. It would be very
conservative to design for a divider current, I
DIV
, of
100 μA. If V
DD
= 5.0V then;
EQUATION
FIGURE 5-3:
V
IN
Circuit.
R
2
= 23.2 k
R
1
=
100 k
NTC Thermistor
100 k
@ 25C
RT
1
I
DIV
V
IN
V
DD
V
DD
x R
2
R
TEMP
(T
1
) + R
2
= V(T
1
)
R
TEMP
(T
2
) + R
2
= V(T
2
)
V
DD
x R
2
Where T
1
and T
2
are the chosen temperatures and
R
TEMP
is the parallel combination of the thermistor
and R
1
.
Minimum Speed
Full Speed
V
MIN
=
x (1.4) + 1.25V
1000
2500
V
MIN
=
x (1.4) + 1.25V = 1.81V
R
1
+ R
2
I
DIV
= 100μA = 5.0V
R
1
+ R
2
= 5.0V
= 50k
100μA
R
2
R
1
GND
V
DD
V
MIN
I
DIV
I
IN
相关PDF资料 |
PDF描述 |
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| TC642EV | PWM Fan Speed Controller with FanSense⑩ Technology |
| TC654EUN | Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC642DEMO | 制造商:Microchip Technology Inc 功能描述:Tools Development kit For Use |
| TC642EOA | 功能描述:马达/运动/点火控制器和驱动器 w/Fault Dtct 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 |
| TC642EOA713 | 功能描述:马达/运动/点火控制器和驱动器 w/Fault Dtct 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 |
| TC642EPA | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controller with FanSense⑩ Technology |
| TC642EUA | 功能描述:马达/运动/点火控制器和驱动器 w/Fault Dtct 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 |
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