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參數(shù)資料
| 型號： | THMC45 |
| 廠商： | TEXAS INSTRUMENTS INC |
| 元件分類： | 運(yùn)動控制電子 |
| 英文描述： | BRUSHLESS DC MOTOR CONTROLLER, 0.25 A, PDSO8 |
| 封裝： | PLASTIC, HTSSOP-8 |
| 文件頁數(shù)： | 3/14頁 |
| 文件大?。?/td> | 157K |
| 代理商： | THMC45 |
PRODUCT PREVIEW documents contain information on new
products in the definition Phase. Characteristic data and other
data specifications are subject to change without notice. This
document is to be used for discussion only and should not be
used as the basis for any design.
thmc45.doc
Copyright
2000 Texas Instruments
!TI Strictly Private !
11
THMC45
SINGLE-PHASE 5VDC BRUSHLESS FAN DRIVER WITH SINGLE WIRE CONTROL INTERFACE
Product Preview
PWM Input Pin (PWM)
The PWM input pin provides several functions for the THMC45. Not only does it serve as the PWM
drive frequency and duty cycle input reference, but it also provides a current sink pulse on the first
rising edge of the PWM input signal after a commutation change. Also, if a transition is not detected on
the PWM pin within 200s (typical), the THMC45 will enter a low-current sleep state. The THMC45
return to a run state on the next rising edge of the PWM input signal.
The THMC45 requires a TTL level PWM input signal from another device, such as the Texas
Instruments THMC11 or a PWM output from a Super I/O device. This signal, along with the hall sensor
input, is used to PWM the OUTA and OUTB outputs according to the truth table in Table 1.
It is recommended that the frequency of the PWM input signal be between 20kHz and 40kHz. Keeping
the PWM frequency at or above 20kHz ensures quiet fan operation by having the PWM frequency
above audible range. Frequencies above 20kHz also permits efficient fan speed control by keeping the
PWM period below the electrical L/R time constant of the motor. This allows continuous current in the
fan windings (see Figure 4). Keeping the PWM frequency below 40kHz minimizes switching losses
typically seen at higher frequencies, which decreases overall efficiency.
The speed of the cooling fan can be varied by adjusting the duty cycle of the PWM input signal. The
higher the duty cycle of the PWM input signal, the higher the current in the fan windings, and thus the
faster the cooling fan will run.
Figure 4: Motor Current Waveform
I
MOTOR
PWM
t
ON
t
OFF
I
DRIVE
I
RECIRCULATE
t
PWM
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