DRV8307_15 Datasheet, PDF (12/34 Pages) Texas Instruments – DRV8307 Brushless DC Motor Controller

DRV8307
SLVSCK2 – APRIL 2014
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Feature Description (continued)
When in the standby state:
• The motor driver circuitry is disabled (all gate drive outputs are driven low, so the FET outputs are high-
impedance).
• The gate drive regulator and charge pump are disabled.
• The VREG regulator and VSW power switch are disabled.
• All analog circuitry is placed into a low power state.
• The digital circuitry in the device still operates.
All internal logic is reset in two different ways:
• Upon device power-up
• When VM drops below V_RESET
An internal clock generator provides all timing for the DRV8307 device. The master oscillator runs at 100 MHz.
This clock is divided to a nominal 50-MHz frequency that clocks the remainder of the digital logic.
8.3.4 Commutation
For 3-phase brushless DC motors, rotor position feedback is provided from Hall effect transducers mounted on
the motor. These transducers provide three overlapping signals, each 60° apart. The windings are energized in
accordance with the signals from the Hall sensors to cause the motor to move.
In addition to the Hall sensor inputs, commutation is affected by a direction control, which alters the direction of
motion by reversing the commutation sequence. Control of commutation direction is by the DIR input terminal.
If the commanded direction changes while the motor is moving, the device allows the motor to coast until the
motor stops. The stopped condition is determined by measuring the period of the HALL_U signal; when the
period exceeds 160 ms, typical operation resumes and the motor starts spinning in the commanded direction.
This prevents excessive current flow in the output stage if the motor is reversed while running at speed.
In standard 120° commutation, mis-positioning the Hall sensors can cause motor noise, vibration, and torque
ripple. 120° commutation using a single Hall sensor (single-Hall commutation) can improve motor torque ripple
and vibration because it relies on only one Hall edge for timing.
8.3.4.1 120° 3-Hall Commutation
In standard 120° commutation, the motor phases are energized using simple combination logic based on all
three Hall sensor inputs.
Standard 120° commutation is in accordance with Table 1, Figure 5, and Figure 6:
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