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参数资料
| 型号： | TC649VOART |
| 元件分类： | 运动控制电子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, PDSO8 |
| 封装： | SOIC-8 |
| 文件页数： | 16/17页 |
| 文件大小： | 119K |
| 代理商： | TC649VOART |
8
TC649-2 12/05/00
TC649
PWM Fan Speed Controller with Auto-Shutdown
2001 Microchip Technology Inc.
DS21449A
VDD x R2
RTEMP (t1) + R2
= V(t1)
VDD x R2
RTEMP (t2) + R2
= V(t2)
Equation 1.
Where t1 and t2 are the chosen temperatures, and
RTEMP is the parallel combination of the thermistor and R1.
These two equations permit solving for the two unknown
variables, R1 and R2. Note that resistor R1 is not absolutely
necessary, but it helps to linearize the response of the
network.
Auto-Shutdown Temperature Design
A voltage divider on VAS sets the temperature where the
part is automatically shut down if the sensed temperature at
VIN drops below the set temperature at VAS (i.e. VIN < VAS).
As with the VIN inputs, 1.25V to 2.65V corresponds to
the temperature range of interest from t1 to t2, respectively.
Assuming that the temperature sensor network designed
above is linearly related to temperature, the shutdown
temperature tAS is related to t2 and t1 by:
2.65V – 1.25V = VAS – 1.25
t2 – t1
tAS – t1
VAS =
( 1.4V ) (tAS – t1) + 1.25
t2 – t1
Equation 2.
For example, if 1.25V and 2.65V at VIN corresponds to
a temperature range of t1 = 0
°C to t2 = 125°C, and the auto-
shutdown temperature desired is 25
°C, then VAS voltage is:
VAS =
1.4V
(25 – 0) + 1.25 = 1.53V
(125 – 0)
Equation 3.
The VAS voltage may be set using a simple resistor
divider as shown in Figure 4. Per the
Electrical Characteris-
tics, the leakage 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…
IDIV = 1e–4 A =
5.0V
, therefore
R1 + R2
R1 + R2 = 5.0V = 50,000
= 50k
1e–4A
We can further specify R1 and R2 by the condition that
the divider voltage is equal to our desired VAS. This yields
the equation:
VAS = VDD x
R2
R1 + R2
Equation 5.
Solving for the relationship between R1 and R2 results in:
R1 = R2 x
VDD – VAS
= R2 x
5 – 1.53
VAS
1.53
Equation 6.
In the case of this example, R1 = (2.27) R2. Substituting
this relationship back into Equation 4 yields the resistor
values:
R2 = 15.3k
, and
R1 = 34.7k
In this case, the standard values of 35k
and 15k are
very close to the calculated values and would be more than
adequate.
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 commuta-
tion pulses at low speeds. Typically, this only occurs at very
low duty-cycles (25% or less). It is a natural consequence of
low PWM duty-cycles. Recall that the SENSE function
detects commutation of the fan as disturbances in the
current through RSENSE. These can only occur when the fan
is energized, 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 TC649 may fail to capture a
pulse within the 32-cycle Missing Pulse Detector window.
When 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 will accelerate briefly when the
Diagnostic Timer fires. For this reason, it is recommended
that VAS be set no lower than 1.8V.
Equation 4.
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相关代理商/技术参数 |
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| TC649VOATR | 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 |
| TC649VPA | 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 |
| TC649VUA | 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 |
| TC649VUATR | 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 |
| TC6-4A11 | 制造商:FERROXCUBE 制造商全称:Ferroxcube International Holding B.V. 功能描述:Ferrite toroids |
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