THMC40, THMC41

VARIABLE SPEED 12-VDC BRUSHLESS FAN MOTOR DRIVERS

SLIS097 – MARCH 2000

1

POST OFFICE BOX 655303

External Power Drive Stage Required

0–2.5 V DC Control Voltage – Suited for

Cooling Fan Applications Requiring

Variable RPM to Reduce Noise and/or

Increase MTBF

PWM Input Signal for Greater System-Level

Flexibility

ON/OFF Power Device – Suited for Cooling

Fans in

Instantly Available PCs

Control of Multiple Fans With a Single

Signal

THMC41) With Open-Drain Output

Indication (THMC41)

Entire RPM Range (THMC40)

Use of Low-Cost Hall Effect Position

Sensor

Output Drivers

1

2

3

4

5

6

7

14

13

12

11

10

9

8

TACH

CP

NC

PGND

H+

H–

PHA

PHB

AGND

NC

THMC40 ...TACH OUTPUT

14-Pin SOP D Package

(TOP VIEW)

1

2

3

4

5

6

7

14

13

12

11

10

9

8

RD

CP

NC

PGND

H+

H–

PHA

PHB

AGND

NC

THMC41 . . . RD OUTPUT

14-Pin SOP D Package

(TOP VIEW)

description

The THMC40 and THMC41 are 2-phase, dc brushless motor (BLM) drive and control devices intended for use

with 12-Vdc cooling fans. Both devices include a high-efficiency PWM drive topology using integrated 0.5-

Ω

(typical) LDMOS drivers, plus a speed control input stage to provide the industry’s first solution for efficient

speed control

inside dc cooling fans. This patented solution eliminates the need for power drive components

on the main system board, thus reducing printed-circuit board (PCB) component count, PCB space, and

assembly time. This solution also offers other advantages over the two commonly used fan speed control

methods, adjustable external dc supply voltage, and adjustable external PWM drive duty cycle.

Unlike other methods which control speed external to the cooling fan, the THMC40 and THMC41 high-efficiency

PWM drive stage adjusts only the level of motor phase winding power. All other circuitry inside the fan obtains

power from the fixed dc voltage fan supply. This method eliminates the typical problem associated with an

external dc voltage regulation method causing loss of headroom to internal control circuitry at low fan supply

voltage and the resulting limitation of low-speed operation to

≈40%. The PWM drive method employed by the

THMC40 and THMC41 also reduces fan supply power consumption over the external linear regulation method,

which has V

×I power loss due to the voltage drop across the regulator.

An external PWM drive method disrupts power to the motor and also to all internal fan circuitry. The THM40 and

THMC41 solution maintains all signal integrity with phase drive commutation and tachometer, while providing

reliable low speed fan operation down to 11% PWM. This method allows fan health monitoring over the full fan

speed range.

Copyright

© 2000, Texas Instruments Incorporated

PRODUCTION DATA information is current as of publication date.

Products conform to specifications per the terms of Texas Instruments

standard warranty. Production processing does not necessarily include

testing of all parameters.

Please be aware that an important notice concerning availability, standard warranty, and use in critical applications of

Texas Instruments semiconductor products and disclaimers thereto appears at the end of this data sheet.