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参数资料
| 型号： | TC646VUA |
| 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： | 4/28页 |
| 文件大小： | 473K |
| 代理商： | TC646VUA |
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TC646
DS21446C-page 12
2002 Microchip Technology Inc.
FIGURE 5-3:
VAS CIRCUIT
Per Section 1.0, “Electrical Characteristics”, the leak-
age current at the VAS pin is no more than 1 A. It is
conservative to design for a divider current, IDIV, of
100 A. If VDD = 5.0V then…
EQUATION
We can further specify R1 and R2 by the condition that
the divider voltage is equal to our desired VAS. This
yields:
EQUATION
Solving for the relationship between R1 and R2 results
in:
EQUATION
In the case of this example, R1 = (2.27) R2.
Substituting this relationship back into the original
equation yields the resistor values:
R2 = 15.3 k, and
R1 = 34.7 k
In this case, the standard values of 34.8 k
and
15.4 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 TC646 “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 TC646 may fail
to capture a pulse within the 32-cycle missing pulse
detector window. If 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 VAS
be set no lower than 1.8V.
5.4
FanSense Network
(RSENSE and CSENSE)
The FanSense network, comprised of RSENSE and
CSENSE, allows the TC646 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
necessary amount of gain (i.e., the current-to-voltage
conversion 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
results in reasonable values for RSENSE. Figure 5-4
illustrates a typical SENSE network. Figure 5-5 shows
the waveforms observed using a typical SENSE net-
work.
R2
R1
GND
VDD
VAS
IDIV
IIN
R1 + R2
IDIV = 1e
–4A =
, therefore
5.0V
R1 + R2 =
= 50,000
= 50k
1e–4A
5.0V
VAS =
VDD x R2
R1 + R2
R1 = R2 x
= R2 x
VDD - VAS
VAS
5 - 1.53
1.53
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相关代理商/技术参数 |
参数描述 |
|---|---|
| TC646VUA713 | 功能描述:马达/运动/点火控制器和驱动器 Shtdn & 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 |
| TC647 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controller with FanSense Technology |
| TC647_13 | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controller with FanSensea?￠ Technology |
| TC647B | 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 |
| TC647BEOA | 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 |
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