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| 型号： | TC642BEOA713 |
| 元件分类： | 运动控制电子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, PDSO8 |
| 封装： | 0.150 INCH, PLASTIC, SOIC-8 |
| 文件页数： | 13/34页 |
| 文件大小： | 683K |
| 代理商： | TC642BEOA713 |
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TC642B/TC647B
DS21756B-page 20
2003 Microchip Technology Inc.
FIGURE 5-5:
Fan Current During a Locked Rotor Condition.
5.5
Output Drive Device Selection
The TC642B/TC647B is designed to drive an external
NPN transistor or N-channel MOSFET as the fan
speed modulating element. These two arrangements
are shown in Figure 5-7. For lower current fans, NPN
transistors are a very economical choice for the fan
drive device. It is recommended that, for higher current
fans (300 mA and above), MOSFETs be used as the
fan drive device. Table 5-2 provides some possible part
numbers for use as the fan drive element.
When using a NPN transistor as the fan drive element,
a base current-limiting resistor must be used, as is
shown in Figure 5-7.
When using MOSFETs as the fan drive element, it is
very easy to turn the MOSFETs on and off at very high
rates. Because the gate capacitances of these small
MOSFETs are very low, the TC642B/TC647B can
charge and discharge them very quickly, leading to
very fast edges. Of key concern is the turn-off edge of
the MOSFET. Since the fan motor winding is essentially
an inductor, once the MOSFET is turned off, the current
that was flowing through the motor wants to continue to
flow. If the fan does not have internal clamp diodes
around the windings of the motor, there is no path for
this current to flow through, and the voltage at the drain
of the MOSFET may rise until the drain-to-source rating
of the MOSFET is exceeded. This will most likely cause
the MOSFET to go into avalanche mode. Since there is
very little energy in this occurrence, it will probably not
fail the device, but it would be a long-term reliability
issue.
The following is recommended:
Ask how the fan is designed. If the fan has clamp
diodes internally, this problem will not be seen. If
the fan does not have internal clamp diodes, it is a
good idea to put one externally (Figure 5-6). Put-
ting a resistor between VOUT and the gate of the
MOSFET will also help slow down the turn-off and
limit this condition.
FIGURE 5-6:
Clamp Diode For Fan Turn-
Off.
Q1
GND
RSENSE
VOUT
Q1: N-Channel MOSFET
FAN
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC642BEOAG | 制造商:Microchip Technology 功能描述:Fan Control Demo Board |
| TC642BEOATR | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controllers With Minimum Fan Speed, Fan Restart and FanSense⑩ Technology for Fault Detection |
| TC642BEPA | 功能描述:马达/运动/点火控制器和驱动器 w/Rstrt & Flt 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 |
| TC642BEPA713 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controllers With Minimum Fan Speed, Fan Restart and FanSense⑩ Technology for Fault Detection |
| TC642BEPATR | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controllers With Minimum Fan Speed, Fan Restart and FanSense⑩ Technology for Fault Detection |
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