- 您现在的位置：买卖IC网 > PDF目录384955 > TC642DEMO (Microchip Technology Inc.) PWM Fan Speed Controller with FanSense⑩ Technology PDF资料下载
参数资料
| 型号： | TC642DEMO |
| 厂商： | Microchip Technology Inc. |
| 英文描述： | PWM Fan Speed Controller with FanSense⑩ Technology |
| 中文描述： | 与FanSense PWM风扇速度控制器⑩技术 |
| 文件页数： | 12/28页 |
| 文件大小： | 485K |
| 代理商： | TC642DEMO |
第1页第2页第3页第4页第5页第6页第7页第8页第9页第10页第11页当前第12页第13页第14页第15页第16页第17页第18页第19页第20页第21页第22页第23页第24页第25页第26页第27页第28页
TC642
DS21444C-page 12
2002 Microchip Technology Inc.
Table 5-1 lists recommended values for 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 may
not be 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 TC642 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. Three
possible 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 TC642’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 (Figure 5-6).
FIGURE 5-6:
R
BASE
.
The correct value for this resistor can be determined as
follows:
Circuit For Determining
V
OH
V
RSENSE
V
RBASE
I
BASE
=
V
RSENSE
+ V
BE(SAT)
+ V
RBASE
= I
FAN
x R
SENSE
= R
BASE
x I
BASE
= I
FAN
/ h
FE
V
OH
is specified as 80% of V
DD
in Section 1.0, “Electri-
cal Characteristics”; V
BE(SAT)
is given in the chosen
transistor’s data sheet.
It is now possible to solve for
R
BASE
.
EQUATION
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
Q
1
GND
V
DD
R
SENSE
R
BASE
V
OH
= 80% V
DD
+ V
RBASE
–
+ V
BE(SAT)
–
+
V
RSENSE
–
Fan
R
BASE
=
V
OH
- V
BE(SAT)
- V
RSENSE
I
BASE
相关PDF资料 |
PDF描述 |
|---|---|
| TC642 | PWM Fan Speed Controller with FanSense⑩ Technology |
| TC642EV | PWM Fan Speed Controller with FanSense⑩ Technology |
| TC654EUN | Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
| TC655EUN | Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
| TC654 | Dual SMBus⑩ PWM Fan Speed Controllers With Fan Fault Detection |
相关代理商/技术参数 |
参数描述 |
|---|---|
| TC642DEMO | 制造商:Microchip Technology Inc 功能描述:Tools Development kit For Use |
| TC642EOA | 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 |
| TC642EOA713 | 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 |
| TC642EPA | 制造商:MICROCHIP 制造商全称:Microchip Technology 功能描述:PWM Fan Speed Controller with FanSense⑩ Technology |
| TC642EUA | 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 |
发布紧急采购，3分钟左右您将得到回复。