DRV10866_15 Datasheet, PDF (9/22 Pages) Texas Instruments – 5V, 3Phase, Sensorless BLDC Motor Driver

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DRV10866
SBVS206A – NOVEMBER 2012 – REVISED MARCH 2015
Feature Description (continued)
7.3.6 Undervoltage Lockout (UVLO)
The DRV10866 has a built-in UVLO function block. The hysteresis of UVLO threshold is 150 mV. The device will
be locked out when V_CC reaches 1.65 V and woke up at 1.8 V.
7.3.7 Thermal Shutdown
The DRV10866 has a built-in thermal shunt down function, which will shut down the device when the junction
temperature is over 160°C and will resume operating when the junction temperature drops back to 150°C.
7.4 Device Functional Modes
7.4.1 Start-up
At start-up with motor at standstill, commutation logic starts to drive the motor in open-loop with U-phase high, V-
phase low, and the W-phase shut off. During open-loop start-up phase, commutation logic advance to next state
automatically as per Table 1 with duty cycle of 100% regardless of PWM input. At each state, commutation logic
detects zero-crossing of back-emf at shut-off phase. Once motor reaches to sufficient speed to allow four
consecutive successful back-emf zero-crossing, commutation logic switches to closed-loop operation mode as
explained in next section.
In certain cases, the motor may have initial speed in forward direction when the device attempts to start-up the
motor again. When this occurs, device commutation logic jumps over the open-loop start-up process and goes to
closed loop directly. By re-synchronizing to the spinning motor, the user achieves the fastest possible start-up
time for this initial condition.
7.4.2 Motor Running at Steady-State Speed
Once open-loop acceleration phase is over, motor steady state speed is determined by applied duty-cycle at
PWM input. In this mode, communication logic steps thought the six states mentioned in Table 1 and next
commutation state is determined by actual back-emf zero-crossing event at shut-off phase. Each state remains
for 150°. This is an advanced trapezoidal method that allows the device to drive the phases gradually to the
maximum current and gradually to 0. Commutation logic also provides the required 15° angle-advance from zero-
crossing events to efficiently commutate the motor.
For a given duty-cycle input, motor speed can be different depending upon the motor loading conditions. Device
provides motor speed information at FG pin which can be used to achieve closed-loop speed control to get
constant speed at varying load condition.
7.4.3 Motor Stopping
Motor can be decelerated gradually by slowly reducing the PWM duty command to avoid overvoltage at DC
input. When the device is commanded to decelerate very fast or stop the motor suddenly from high speed, in
order to protect the IC and the system, the DRV10866 goes into AVS protection, as explained in Voltage Surge
Protection.
COMMUTATION STATE
State 1
State 2
State 3
State 4
State 5
State 6
Table 1. Commutation Table
PHASE_U
High
High
Off
Low
Low
Off
PHASE_V
Low
Off
High
High
Off
Low
PHASE_W
Off
Low
Low
Off
High
High
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