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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： | 5/34页 |
| 文件大小： | 683K |
| 代理商： | TC642BEOA713 |
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2003 Microchip Technology Inc.
DS21756B-page 13
TC642B/TC647B
FIGURE 4-4:
VIN voltage vs. PWM duty
cycle(Typical).
The PWM duty cycle is also controlled by the VMIN pin
more details on this function.
4.5
Minimum Speed (VMIN Pin)
For the TC642B and TC647B devices, pin 3 is the VMIN
pin. This pin is used for setting the minimum fan speed
threshold.
The minimum fan speed function provides a way to set
a threshold for a minimum duty cycle on the VOUT out-
put. This in turn produces a minimum fan speed for the
user. The voltage range for the VMIN pin is the same as
that for the VIN pin (1.20V to 2.60V). The voltage at the
VMIN pin is set in this range so that as the voltage at the
VIN pin decreases below the VMIN voltage, the output
duty cycle will be controlled by the VMIN voltage. The
following equation can be used to determine the neces-
sary voltage at VMIN for a desired minimum duty cycle
on VOUT.
EQUATION
VMIN VOLTAGE
Example: If a minimum duty cycle of 40% is desired,
the VMIN voltage should be set to:
EXAMPLE 4-1:
If the voltage at the VIN pin falls below 1.76V, the duty
cycle of the VOUT output will not decrease below the
40% value that is now set by the voltage at the VMIN
pin. In this manner, the fan will continue to operate at
40% speed even when the temperature (voltage at VIN)
continues to decrease.
For the TC642B and TC647B devices, the VMIN pin is
also used as the shutdown pin. The VSHDN and VREL
threshold voltages are characterized in the “Electrical
voltage is pulled below the VSHDN threshold, the device
will shut down (VOUT output goes to a low state, the
FAULT pin is inactive). If the voltage on the VMIN pin
then rises above the release threshold (VREL), the
device will go through a Power-Up sequence. The
Power-Up sequence is shown later in Figure 4-9.
4.6
VOUT Output (PWM Output)
The VOUT output is a digital output designed for driving
the base of a transistor or the gate of a MOSFET. The
VOUT output is designed to be able to quickly raise the
base current or the gate voltage of the external drive
device to its final value.
When the device is in shutdown mode, the VOUT output
is actively held low. The output can be varied from 0%
duty cycle (full off) to 100% duty cycle (full on). As pre-
viously discussed, the duty cycle of the VOUT output is
controlled via the VIN input voltage along with the VMIN
voltage.
A base current-limiting resistor is required when using
a transistor as the external drive device in order to limit
the amount of drive current that is drawn from the VOUT
output.
The VOUT output can be directly connected to the gate
of an external MOSFET. One concern when doing this,
though, is that the fast turn-off time of the fan drive
MOSFET can cause a problem. The fan motor looks
like an inductor. When the MOSFET is turned off
quickly, the current in the fan wants to continue to flow
in the same direction. This causes the voltage at the
drain of the MOSFET to rise. If there aren’t any clamp
diodes internal to the fan, this voltage can rise above
the drain-to-source voltage rating of the MOSFET. For
this reason, an external clamp diode is suggested. This
is shown in Figure 4-5.
0
10
20
30
40
50
60
70
80
90
100
1
1.2
1.4
1.6
1.8
2
2.2
2.4
2.6
2.8
VIN (V)
Duty
Cycle
(%)
VMIN (V) = (DC * 1.4) + 1.20
DC = Desired Duty Cycle
100
VMIN (V) = (40 * 1.4) + 1.20
100
VMIN = 1.76V
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相关代理商/技术参数 |
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| 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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