參數(shù)資料
型號(hào)： TC654
廠商： Microchip Technology Inc.
英文描述： Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection
中文描述： 雙PWM風(fēng)扇的SMBus⑩故障檢測(cè)與風(fēng)扇轉(zhuǎn)速控制器
文件頁(yè)數(shù)： 12/36頁(yè)
文件大?。?/td> 706K
代理商： TC654
TC654/TC655
DS21734A-page 12
2002 Microchip Technology Inc.
FIGURE 4-6:
Network.
NTC Thermistor Sensor
The second method for controlling the duty cycle of the
PWM output (V
OUT
) is via the SMBus interface. In order
to control the PWM duty cycle via the SMBus, DUTYC
(bit 5<0>) of the Configuration Register (Register 6.3)
must be set to a ‘
1
’. This tells the TC654/TC655 device
that the duty cycle should be controlled by the Duty
Cycle Register. Next, the Duty Cycle Register must be
programmed to the desired value. The Duty Cycle Reg-
ister is a 4 Bit read/write register that allows duty cycles
from 30% to 100% to be programmed. Table 4-1 shows
the binary codes for each possible duty cycle.
TABLE 4-1:
DUTY-CYCLE REGISTER
(DUTY-CYCLE) 4-BITS,
READ/WRITE
This method of control allows for more sophisticated
algorithms to be implemented by utilizing microcontrol-
lers or microprocessors in the system. In this way, mul-
tiple system temperatures can be taken into account for
determining the necessary fan speed.
As shown in Table 4-1, the duty cycle has more of a
step function look than did the V
IN
control approach.
Because the step changes in duty cycle are small, they
are rarely audibly noticeable, especially when the fans
are integrated into the system.
4.6
PWM Output (V
OUT
)
The V
OUT
pin is designed to drive two low cost NPN
transistors or N-channel MOSFETs as the low side
power switching elements in the system as is shown in
Figure 4-7. These switching elements are used to turn
the fans on and off at the PWM duty cycle commanded
by the V
OUT
output.
This output has complementary drive (pull up and pull
down) and is optimized for driving NPN transistors or
N-channel MOSFETs (see Section 2.0 for sink and
source current capability of the V
OUT
drive stage).
The external device needs to be chosen to fit the volt-
age and current rating of the fan in a particular applica-
tion (Refer to Section 7.5 Output Drive Device
Selection). NPN transistors are often a good choice for
low current fans. If a NPN transistor is chosen, a base
current limiting resistor should be used. When using a
MOSFET as the switching element, it is sometimes a
good idea to have a gate resistor to help slow down the
turn on and turn off of the MOSFET. As with any switch-
ing waveform, fast rising and falling edges can
sometimes lead to noise problems.
As previously stated, the V
OUT
output will go to 100%
duty cycle during power up and release from shutdown
conditions. The V
OUT
output only shuts down when
commanded to do so via the Configuration Register
(SDM (bit 0<0>)). Even when a locked rotor condition
is detected, the V
OUT
output will continue to pulse at
the programmed duty cycle.
4.7
Sensing Fan Operation (SENSE1 &
SENSE2)
The TC654 and TC655 also feature Microchip's propri-
etary FanSense technology. During normal fan opera-
tion, commutation occurs as each pole of the fan is
energized. The fan current pulses created by the fan
commutation are sensed using low value current sense
resistors in the ground return leg of the fan circuit. The
voltage pulses across the sense resistor are then AC
coupled through capacitors to the SENSE pins of the
TC654/TC655 device. These pulses are utilized for cal-
culating the RPM of the individual fans. The threshold
voltage for the SENSE pins is 100 mV (typical). The
peak of the voltage pulse at the SENSE pins must
exceed the 100 mV (typical) threshold in order for the
pulse to be counted in the fan RPM measurement.
Duty-Cycle Register (Duty Cycle)
D(3)
D(2)
D(1)
D(0)
Duty-Cycle
0
0
0
0
30%
0
0
0
1
34.67%
0
0
1
0
39.33% (default for V
IN
open and when SMBus
is not selected)
0
0
1
1
44%
0
1
0
0
48.67%
0
1
0
1
53.33%
0
1
1
0
58%
0
1
1
1
62.67%
1
0
0
0
67.33%
1
0
0
1
72%
1
0
1
0
76.67%
1
0
1
1
81.33%
1
1
0
0
86%
1
1
0
1
90.67%
1
1
1
0
95.33%
1
1
1
1
100%
V
IN
+5 V
NTC Thermistor
100 k
@ 25°C
R
1
R
2
C
1
0.01 μF
TC654/
TC655
GND
34.8 k
14.7 k
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PDF描述
TC655 Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection
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參數(shù)描述
TC654EUN 功能描述:軟開(kāi)關(guān) PWM 控制器 Dual RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
TC654EUNTR 功能描述:軟開(kāi)關(guān) PWM 控制器 Dual RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
TC655 制造商:MICROCHIP 制造商全稱(chēng):Microchip Technology 功能描述:Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection
TC655EUN 功能描述:軟開(kāi)關(guān) PWM 控制器 Dual RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
TC655EUNTR 功能描述:軟開(kāi)關(guān) PWM 控制器 Dual RoHS:否 制造商:Fairchild Semiconductor 輸出端數(shù)量: 輸出電流: 開(kāi)關(guān)頻率: 工作電源電壓:30 V 電源電流: 最大工作溫度:+ 105 C 最小工作溫度:- 40 C 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SOIC-8 封裝:Reel
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