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| 型号： | TC642EUA |
| 元件分类： | 运动控制电子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, PDSO8 |
| 封装： | PLASTIC, MSOP-8 |
| 文件页数： | 3/28页 |
| 文件大小： | 485K |
| 代理商： | TC642EUA |
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2002 Microchip Technology Inc.
DS21444C-page 11
TC642
We can further specify R1 and R2 by the condition that
the divider voltage is equal to our desired VMIN. This
yields the following equation:
EQUATION
Solving for the relationship between R1 and R2 results
in the following equation:
EQUATION
In this example, R1 = (1.762) R2. Substituting this rela-
tionship back into the previous equation yields the
resistor values:
R2 = 18.1 k, and R1 = 31.9 k
In this case, the standard values of 31.6 k
and
18.2 k
are very close to the calculated values and
would be more than adequate.
5.3
Operations at Low Duty Cycle
One boundary condition which may impact the selec-
tion of the minimum fan speed is the irregular activation
of the Diagnostic Timer due to the TC642 “missing” fan
commutation pulses at low speeds. This is a natural
consequence of low PWM duty cycles (typically 25% or
less). Recall that the SENSE function detects commu-
tation of the fan as disturbances in the current through
RSENSE. These can only occur when the fan is ener-
gized (i.e., VOUT is “on”). At very low duty cycles, the
VOUT output is “off” most of the time. The fan may be
rotating normally, but the commutation events are
occurring during the PWM’s off-time.
The phase relationship between the fan’s commutation
and the PWM edges tends to “walk around” as the
system operates. At certain points, the TC642 may fail
to capture a pulse within the 32-cycle missing pulse
detector window. When this happens, the 3-cycle
Diagnostic Timer will be activated, the VOUT output will
be active continuously for three cycles and, if the fan is
operating normally, a pulse will be detected. If all is
well, the system will return to normal operation. There
is no harm in this behavior, but it may be audible to the
user as the fan accelerates briefly when the Diagnostic
Timer fires. For this reason, it is recommended that
VMIN be set no lower than 1.8V.
5.4
FanSense Network
(RSENSE and CSENSE)
The FanSense network, comprised of RSENSE and
CSENSE, allows the TC642 to detect commutation of
the fan motor (FanSense technology). This network
can be thought of as a differentiator and threshold
detector. The function of RSENSE is to convert the fan
current into a voltage. CSENSE serves to AC-couple this
voltage signal and provide a ground-referenced input to
the SENSE pin. Designing a proper SENSE network is
simply a matter of scaling RSENSE to provide the nec-
essary amount of gain (i.e., the current-to-voltage con-
version ratio). A
0.1 F ceramic capacitor is
recommended for CSENSE. Smaller values require
larger sense resistors, and higher value capacitors are
bulkier and more expensive. Using a 0.1 F capacitor
illustrates a typical SENSE network. Figure 5-5 shows
the waveforms observed using a typical SENSE net-
work.
FIGURE 5-4:
SENSE Network.
FIGURE 5-5:
SENSE Waveforms.
VDD x R2
R1 + R2
VMIN =
VDD - VMIN
VMIN
R1 = R2 x
Q1
GND
VDD
RSENSE
SENSE
RBASE
CSENSE
(0.1
F Typ.)
VOUT
Fan
1
Ch1
100mV
Tek Run: 10.0kS/s Sample
Ch2
100mV
M5.00ms
Ch1
142mV
GND
[
T
]
T
Waveform @ Sense Resistor
90mV
50mV
GND
Waveform @ Sense Pin
2
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相关代理商/技术参数 |
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| TC642EUA713 | 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 |
| TC642EV | 功能描述:电源管理IC开发工具 For TC642/6/7/8/9 RoHS:否 制造商:Maxim Integrated 产品:Evaluation Kits 类型:Battery Management 工具用于评估:MAX17710GB 输入电压: 输出电压:1.8 V |
| TC642EV | 制造商:Microchip Technology Inc 功能描述:Tools Development kit For Use |
| TC642VOA | 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 |
| TC642VOA713 | 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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