THMC40, THMC41

VARIABLE SPEED 12-VDC BRUSHLESS FAN MOTOR DRIVERS

SLIS097 – MARCH 2000

2

POST OFFICE BOX 655303

description (continued)

This terminal allows controlling the fan speed via a DAC output from an external control IC or an RC-filtered

PWM output from a PC Super I/O chip.

The THMC40 and THMC41 have an internal Hall sensor amplifier and signal conditioner, global thermal

shutdown, locked rotor protection, and automatic restart after a locked rotor condition. The THMC40 provides

an open-drain tachometer output signal, while the THMC41 provides an open-drain locked rotor detection

output signal. These devices also provide a sleep-state mode to eliminate the need for an external power

component to disconnect the fan from the supply during a system sleep state or

instantly available power down.

The THMC40 and THMC41 are primarily intended for cooling fan applications that require RPM speed control

and the availability of a tachometer or locked rotor detection signal.

functional block diagram

Tachometer

Output

CP

VPWM

Low-Side

Gate Drive

Control Logic

and Global

Thermal

Shutdown

High-Side Gate

Drive With

Synchronous

Rectification

Charge Pump

Locked Rotor

Detection and

Auto Restart

SLEEP

START and

SLEEP

Detection

PWM

Generator

PWM

Oscillator

23 kHz Nominal

PUC and VREF

Thermal

Shutdown

OSC

VSTART

VSLEEP

OSC

PWM

SLEEP

COSC

TACH

(THMC40)

RD

(THMC41)

VPWR

VOUT

PHA

PHB

H+

H–

PGND

AGND

Hall Sensor

Comparator