THMC45

5V AND 3.3V DC BRUSHLESS FAN MOTOR DRIVER

WITH SINGLE WIRE CONTROL

SLIS101A − MAY 2001

10

POST OFFICE BOX 655303

PRINCIPLES OF OPERATION

locked rotor protection

An internal digital timer is used to monitor the output of the Hall sensor amplifier. When change in commutation

outputs to automatically restart the motor after a locked rotor condition. When the locked rotor condition

continues to exist, the above process repeats itself until the locked condition is removed or the THMC45 is

powered down (see Figure 6).

Conditioned Hall

Amplifier Output

(Internal)

OUTA, OUTB

Enable

t(RD)

t(RETRY)

t(RD)

t(RETRY)

Figure 6. Typical Locked Rotor Protection Timing Waveforms

open-drain tachometer output (TACH)

The TACH output is an open-drain output that is activated by the output of the Hall sensor comparator output.

When the output of the Hall sensor comparator is high, the TACH output floats high. When the output of the Hall

sensor amplifier is low, the TACH output is pulled low. The resulting output signal has two pulses per revolution

on a four-pole motor.

The TACH output can be used to monitor and measure actual fan speed. It may also be used as part of a

closed-loop speed control system.

thermal shutdown

The THMC45 provides protection against excessive device temperature with a thermal sensor to monitor the

the thermal shutdown threshold (175

are re-enabled.