DRV10866 Datasheet, PDF (6/14 Pages) Texas Instruments – 5-V, THREE-PHASE, SENSORLESS BLDC MOTOR DRIVER

DRV10866
SBVS206 – NOVEMBER 2012
www.ti.com
DETAILED DEVICE DESCRIPTION
DRV10866 is a three phase, sensorless motor driver with integrated power MOSFETs with drive current
capability up to 680-mA peak. DRV10866 is specifically designed for low noise, low external component count
fan motor drive applications. DRV10866 has built in over current protection with no external current sense
resistor needed. The synchronous rectification mode of operation achieves increased efficiency for motor driver
applications. DRV10866 can output either FG or ½ FG to indicate motor speed with open drain output through
FGS pin selection. A 150° sensorless BEMF control scheme is implemented for a three phase motor. Voltage
surge protection scheme prevents input V_CC capacitor from over charge during motor acceleration and
deceleration modes. DRV10866 has multiple built-in protection blocks including UVLO, over current protection,
lock protection and thermal shut down protection.
Speed Control
DRV10866 can control motor speed through either the PWM_IN or V_CC pin. Motor speed will increase with higher
PWM_IN duty cycle or V_CC input voltage. The curve of motor speed (RPM) vs PWM_IN duty cycle or V_CC input
voltage is close to linear in most cases. However, motor characteristics will affect the linearity of this speed
curve. DRV10866 can operate at very low V_CC input voltage down to 1.65 V. The PWM_IN pin is pulled up to V_CC
internally and frequency range can vary from 15 kHz to 50 kHz. The motor driver MOSFETs will operate at
constant switching frequency 156 kHz. With this high switching frequency, DRV10866 can eliminate audible
noise and reduce the ripple of V_CC input voltage and current, and thus minimize EMI noise.
Frequency Generator
The FG pin outputs a 50% duty cycle of PWM waveform in the normal operation condition. The frequency of the
FG signal represents the motor speed and phase information. The FG pin is an open drain output, so an external
pull up resistor is needed when connected to an external system. During the startup, FG output will stay at high
impedance until the motor speed reaches a certain level and BEMF is detected. During lock protection condition,
FG output will remain high until the motor restarts and startup process is completed. DRV10866 can output either
FG or ½ FG to indicate motor status with open drain output through FGS pin selection. When FGS is pulled to
V_CC, the frequency of FG output is half of that when FGS is pulled to GND. Motor speed can be calculated based
on the FG frequency when FGS is pulled to GND, which equals to:
RPM =
(FG ? 60)
pole pairs
(1)
Where FG is in hertz (Hz).
Lock Protection
If the motor is blocked or stopped by an external force, the lock protection is triggered after lock detection time.
During lock detection time, the circuit monitors the PWM and FG signals. If PWM has an input signal while the
FG output is in high impedance during this period, the lock protection will be enabled and DRV10866 will stop
driving the motor. After lock release time, DRV10866 will resume driving the motor again. If the lock condition still
exists, DRV10866 will proceed with the next lock protection cycle until the lock condition is removed. With this
lock protection, the motor and device will not get over heated or be damaged.
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