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參數(shù)資料
| 型號： | TC647 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | PWM Fan Speed Controller with FanSense Technology |
| 中文描述： | 與FanSense PWM風(fēng)扇速度控制器技術(shù) |
| 文件頁數(shù)： | 12/28頁 |
| 文件大?。?/td> | 478K |
| 代理商： | TC647 |
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TC647
DS21447C-page 12
2002 Microchip Technology Inc.
FIGURE 5-5:
SENSE Waveforms.
Table 5-1 lists the recommended values of R
SENSE
based on the nominal operating current of the fan. Note
that the current draw specified by the fan manufacturer
may be a worst-case rating for near-stall conditions and
not the fan’s nominal operating current. The values in
Table 5-1 refer to actual average operating current. If
the fan current falls between two of the values listed,
use the higher resistor value. The end result of employ-
ing Table 5-1 is that the signal developed across the
sense resistor is approximately 450 mV in amplitude.
TABLE 5-1:
R
SENSE
VS. FAN CURRENT
5.5
Output Drive Transistor Selection
The TC647 is designed to drive an external transistor
or MOSFET for modulating power to the fan. This is
shown as Q
1
in Figures 3-1, 5-1, 5-4, 5-6, 5-7, 5-8
and 5-9. The V
OUT
pin has a minimum source current
of 5 mA and a minimum sink current of 1 mA. Bipolar
transistors or MOSFETs may be used as the power
switching element, as shown in Figure 5-7. When high
current gain is needed to drive larger fans, two transis-
tors may be used in a Darlington configuration. These
circuit topologies are shown in Figure 5-7: (a) shows a
single NPN transistor used as the switching element;
(b) illustrates the Darlington pair; and (c) shows an N-
channel MOSFET.
One major advantage of the TC647’s PWM control
scheme versus linear speed control is that the power
dissipation in the pass element is kept very low. Gener-
ally, low cost devices in very small packages, such as
TO-92 or SOT, can be used effectively. For fans with
nominal operating currents of no more than 200 mA, a
single transistor usually suffices. Above 200 mA, the
Darlington or MOSFET solution is recommended. For
the fan sensing function to work correctly, it is impera-
tive that the pass transistor be fully saturated when
“on”.
Table 5-2 gives examples of some commonly available
transistors and MOSFETs. This table should be used
as a guide only since there are many transistors and
MOSFETs which will work just as well as those listed.
The critical issues when choosing a device to use as
Q
1
are: (1) the breakdown voltage (V
(BR)CEO
or
V
DS
(MOSFET)) must be large enough to withstand the
highest voltage applied to the fan (
Note:
This will occur
when the fan is off); (2) 5 mA of base drive current must
be enough to saturate the transistor when conducting
the full fan current (transistor must have sufficient
gain); (3) the V
OUT
voltage must be high enough to suf-
ficiently drive the gate of the MOSFET to minimize the
R
DS(on)
of the device; (4) rated fan current draw must
be within the transistor's/MOSFET's current handling
capability; and (5) power dissipation must be kept
within the limits of the chosen device.
A base-current limiting resistor is required with bipolar
transistors. This is shown in Figure 5-6.
Nominal Fan Current (mA)
R
SENSE
(
)
9.1
4.7
3.0
2.4
2.0
1.8
1.5
1.3
1.2
1.0
50
100
150
200
250
300
350
400
450
500
1
Ch1
100mV
Tek Run: 10.0kS/s Sample
T
Ch2
100mV
M5.00ms
Ch1
142mV
GND
[
]
T
Waveform @ Sense Resistor
90mV
50mV
GND
Waveform @ Sense Pin
2
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相關(guān)代理商/技術(shù)參數(shù) |
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| TC647_13 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:PWM Fan Speed Controller with FanSensea?￠ Technology |
| TC647B | 制造商:MICROCHIP 制造商全稱: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:馬達(dá)/運(yùn)動/點(diǎn)火控制器和驅(qū)動器 w/Rstrt & Flt Dtct RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
| TC647BEOA713 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:PWM Fan Speed Controllers With Minimum Fan Speed, Fan Restart and FanSense⑩ Technology for Fault Detection |
| TC647BEOATR | 功能描述:馬達(dá)/運(yùn)動/點(diǎn)火控制器和驅(qū)動器 w/Rstrt & Flt Dtct RoHS:否 制造商:STMicroelectronics 產(chǎn)品:Stepper Motor Controllers / Drivers 類型:2 Phase Stepper Motor Driver 工作電源電壓:8 V to 45 V 電源電流:0.5 mA 工作溫度:- 25 C to + 125 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:HTSSOP-28 封裝:Tube |
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