DRV10983_15 Datasheet, PDF (25/57 Pages) Texas Instruments – DRV10983 12- to 24-V, Three-Phase, Sensorless BLDC Motor Driver

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DRV10983
SLVSCP6B – JULY 2014 – REVISED FEBRUARY 2015
9.4.4.1 Start-Up Current Ramp Up
A fast change in the applied drive current may result in a sudden change in the driving torque. In some
applications, this could result in acoustic noise. To avoid this, the DRV10983 allows the option of limiting the rate
at which the current is applied to the motor. OpLCurrRt[2:0] sets the maximum voltage ramp up rate that will be
applied to the motor. The waveforms in Figure 19 show how this feature can be used to gradually ramp the
current applied to the motor.
Start driving with fast current ramp
Start driving with slow current ramp
Figure 19. Motor Startup Current Ramp
9.4.5 Closed Loop
In closed loop operation, the DRV10983 continuously samples the current in the motor’s U phase and uses this
information to estimate the BEMF voltage that is present. The drive state of the motor is controlled based on the
estimated BEMF voltage.
9.4.5.1 Half Cycle Control and Full Cycle Control
The estimated BEMF used to control the drive state of the motor has two zero-crosses every electrical cycle. The
DRV10983 can be configured to update the drive state either once every electrical cycle or twice for every
electrical cycle. When AdjMode is programmed to 1, half cycle adjustment is applied. The control logic is
triggered at both rising edge and falling edge. When AdjMode is programmed to 0, full cycle adjustment is
applied. The control logic is triggered only at the rising edge (see Figure 20).
Half cycle adjustment provides a faster response when compared with full cycle adjustment. Use half cycle
adjustment whenever the application requires operation over large dynamic loading conditions. Use the full cycle
adjustment for low current (<1 A) applications because it offers more tolerance for current measurement offset
errors.
Zero cross signal
Zero cross signal
Estimated Position
Real Driving Voltage
Real Position
Ideal Driving Voltage
Estimated Position
Real Driving Voltage
Real Position
Ideal Driving Voltage
Adjustment (full cycle)
Adjustment (half cycle)
Figure 20. Closed Loop Control Commutation Adjustment Mode
9.4.5.2 Analog Mode Speed Control
The SPEED input pin can be configured to operate as an analog input (SpdCtrlMd = 0).
When configured for analog mode, the voltage range on the SPEED pin can be varied from 0 to V3P3. If
SPEED > V_{ANA_FS}, the speed command is maximum. If V_{ANA_ZS} ≤ SPEED < V_{ANA_FS} the speed command
changes linearly according to the magnitude of the voltage applied at the SPEED pin. If SPEED < V_{ANA_ZS} the
speed command is to stop the motor. Figure 21 shows the speed command when operating in analog mode.
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