THMC45 Datasheet, PDF (7/16 Pages) Texas Instruments – 5-V AND 3.3-V DC BRUSHLESS FAN MOTOR DRIVER WITH SINGLE WIRE CONTOL

THMC45
5ĆV AND 3.3ĆV DC BRUSHLESS FAN MOTOR DRIVER
WITH SINGLE WIRE CONTROL
SLIS101A − MAY 2001
PRINCIPLES OF OPERATION
H-bridge motor drive outputs (OUTA, OUTB) (continued)
Figures 2a and 2b show THMC45 H-bridge motor drive states with stator winding current being driven from
OUTA to OUTB and from OUTB to OUTA, respectively, based on the Hall sensor commutation state. As shown
during t_ON, PWM signal is high and the drive current is from V_PWR through the activated switches and motor
to GND. PWM occurs on the low side, and the stator winding inductive current recirculates on the high side
during t_OFF and PWM signal is low (see Figure 3 for motor current waveform). Recirculation of inductive current
through the high-side switches during t_OFF, known as synchronous rectification, improves power conversion
efficiency by maintaining energy in the stator winding and results in a continuous dc current level.
VPWR
VPWR
ON M1
PWM tON
M2
OUTA
Motor
OUTB
PWM
OFF M3
I(DRIVE)
M4
PWM
ON M1
I(RECIRCULATE) _M2
PWM
OFF
OUTA
M3
Motor
OUTB
PWM tOFF
M4
PWM
GND
VPWR
H+ H−
H
L
OUTA
H
OUTB
PWM
GND
a) A to B Current Direction
VPWR
PWM
M1
PWM tON
M2
OUTA
Motor
OUTB
PWM _M3
I(DRIVE)
M4
ON
PWM
OFF PWM
M1
I(RECIRCULATE) _M2
OUTA
M3
Motor
OUTB
PWM tOFF
M4
ON
OFF
GND
H+ H−
L
H
OUTA
PWM
OUTB
H
GND
b) B to A Current Direction
Figure 2. H-Bridge PWM Drive With Synchronous Rectification
• POST OFFICE BOX 655303 DALLAS, TEXAS 75265
7