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參數(shù)資料
| 型號(hào)： | TC649 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | PWM Fan Speed Controller with Auto-Shutdown and FanSense Technology(風(fēng)扇監(jiān)控器帶自動(dòng)關(guān)斷功能) |
| 中文描述： | PWM風(fēng)扇帶自動(dòng)調(diào)速器關(guān)斷和FanSense科技（風(fēng)扇監(jiān)控器帶自動(dòng)關(guān)斷功能） |
| 文件頁(yè)數(shù)： | 11/28頁(yè) |
| 文件大?。?/td> | 478K |
| 代理商： | TC649 |
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2002 Microchip Technology Inc.
DS21449C-page 11
TC649
FIGURE 5-3:
V
AS
Circuit.
Per Section 1.0, “Electrical Characteristics”, the leak-
age current at the V
AS
pin is no more than 1 μA. It is
conservative to design for a divider current, I
DIV
, of
100 μA. If V
DD
= 5.0V then:
EQUATION
We can further specify R
1
and R
2
by the condition that
the divider voltage is equal to our desired V
AS
. This
yields the following:
EQUATION
Solving for the relationship between R
1
and R
2
results
in:
EQUATION
In the case of this example, R
1
= (2.27) R
2
. Substituting
this relationship back into the V
AS
equation above
yields the resistor values:
R
2
= 15.3 k
, and
R
1
= 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
selection of the minimum fan speed is the irregular
activation of the Diagnostic Timer due to the TC649
“missing” fan commutation pulses at low speeds. This
is a natural consequence of low PWM duty cycles (typ-
ically 25% or less). Recall that the SENSE function
detects commutation of the fan as disturbances in the
current through R
SENSE
. These can only occur when
the fan is energized (i.e., V
OUT
is “on”). At very low duty
cycles, the V
OUT
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 TC649 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 V
OUT
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 V
AS
be set no lower than 1.8V.
5.4
FanSense
Network
(R
SENSE
and C
SENSE
)
The FanSense network, comprised of R
SENSE
and
C
SENSE
, allows the TC649 to detect commutation of
the fan motor (FanSense technology). This network
can be thought of as a differentiator and threshold
detector. The function of R
SENSE
is to convert the fan
current into a voltage. C
SENSE
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 R
SENSE
to provide the nec-
essary amount of gain (i.e., the current-to-voltage con-
version ratio). A 0.1 μF ceramic capacitor is
recommended for C
SENSE
. Smaller values require
larger sense resistors, and higher value capacitors are
bulkier and more expensive. Using a 0.1 μF capacitor
results in reasonable values for R
SENSE
. Figure 5-4
illustrates a typical SENSE network. Figure 5-5 shows
the waveforms observed using a typical SENSE net-
work.
R2
R1
GND
V
DD
V
AS
I
DIV
I
IN
R
1
+ R
2
I
DIV
= 1e
– 4
A 5.0V
R
1
+ R
2
= 5.0V
= 50 k
1e
–4
A
V
AS
=
V
DD
x R
2
R
1
+ R
2
R
1
= R
2
x = R
2
x
V
- V
V
AS
5 -1.53
1.53
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| TC649_13 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:PWM Fan Speed Controller with Auto-Shutdown and FanSensea?￠ Technology |
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| TC649BEOA | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 w/Rstrt Shtdn & Flt 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 |
| TC649BEOA713 | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:PWM Fan Speed Controllers With Auto-Shutdown, Fan Restart and FanSense⑩ Technology for Fault Detection |
| TC649BEOATR | 功能描述:馬達(dá)/運(yùn)動(dòng)/點(diǎn)火控制器和驅(qū)動(dòng)器 w/Rstrt Shtdn & Flt 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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