THMC40_11 Datasheet, PDF(12/19 Page) Texas Instruments – VARIABLE SPEED 12-VDC BRUSHLESS FAN MOTOR DRIVERS

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THMC40_11 Datasheet, PDF (12/19 Pages) Texas Instruments – VARIABLE SPEED 12-VDC BRUSHLESS FAN MOTOR DRIVERS

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THMC40, THMC41

VARIABLE SPEED 12-VDC BRUSHLESS FAN MOTOR DRIVERS

SLIS097 â MARCH 2000

locked rotor protection

An internal digital timer monitors the output of the Hall sensor amplifier. When a change in commutation state

is not observed within one second (typical with 2200 pF COSC), the VOUT, PHA, and PHB outputs are disabled

for eight seconds (typical with 2200 pF COSC). After the outputs have been disabled for eight seconds (typical

with 2200 pF COSC), the THMC40 and THMC41 re-enable the VOUT, PHA, and PHB outputs to automatically

restart the motor after a locked rotor condition. If the locked rotor condition still exists, the above process repeats

itself until the condition is removed, or the THMC40 and THMC41 are powered down (see Figure 9).

NOTE:

The locked rotor detection time and auto-retry time are proportional to the PWM frequency, and

therefore to the value of COSC. With a COSC value of 2200 pF, the PWM frequency is typically

22.7 kHz, locked rotor detection time is typically one second, and auto-retry time is typically

eight seconds.

Hall Sensor

Comparator

Output

VOUT, PHA and

PHB Output

Enable

RD Output

(THMC41)

Tach Output

(THMC40)

Figure 9. Typical Locked Rotor Protection Timing Waveforms

â¢ POST OFFICE BOX 655303 DALLAS, TEXAS 75265

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