DRV8308_15 Datasheet, PDF (20/60 Pages) Texas Instruments – DRV8308 Brushless DC Motor Controller

DRV8308
SLVSCF7A – FEBRUARY 2014 – REVISED OCTOBER 2014
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Timing of 120° single-Hall commutation is essentially the same as standard 120° commutation shown previously.
However, there are small time differences of when the transitions occur.
8.3.4.3 180° Sine-Wave-Drive Commutation
180° sine-wave-drive commutation uses a single Hall sensor to generate commutation timing, as described for
120° single-Hall commutation. In addition, the value of the commutation timer modulates the duty cycle of the
outputs in accordance with a fixed pattern that approximates sinusoidal current through the windings.
The output of the commutation block is a 12-bit modulation value for each motor phase (U, V, and W) that
represents the duty cycle modulation of the PWM for each output. Note that during 120° commutation, these
values are either 0 or set to a constant value derived from the MOD120 register.
When using sine mode, MOD120 should be set to 3970.
Modulation value
Duty Cycle
Figure 9. 180° Sine-Wave-Drive Commutation
During 180° sine-wave-drive commutation, commutation transitions occur midway between Hall transitions. The
PWM duty cycle is modulated to provide sinusoidal current waveforms. Commutation (shown for asynchronous
rectification) is in accordance with the table and diagrams below. Note that the diagrams show a representation
of duty cycle, not level, for the PWM states.
STATE
1
2
3
4
5
6
1X
2X
Table 3. Commutation for Asynchronous Rectification⁽¹⁾
HALL INPUTS
DIR = 1
DIR = 0
U_H V_H W_H U_H V_H
L
L
H
H
H
L
H
H
H
L
L
H
L
H
L
H
H
L
L
L
H
L
L
L
H
H
L
H
L
H
H
H
H
L
L
L
L
L
H
H
W_H
L
L
H
H
H
L
L
H
PHASE U
U_HSGATE
U_LSGATE
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
L
H
L
H
L
L
L
L
PRE-DRIVE OUTPUTS
PHASE V
V_HSGATE
V_LSGATE
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
L
H
L
H
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
L
L
L
L
PHASE W
W_HSGATE
W_LSGATE
L
H
L
H
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
PWM
L / !PWM⁽²⁾
L
L / !PWM⁽²⁾
L
L
L
L
(1) Hall sensor is "H" if the positive input terminal voltage is higher than the negative input terminal voltage. States 1X and 2X are illegal
input combinations.
(2) During states where the phase is driven with a PWM signal, using asynchronous rectification, the LS gate is held off (L); using
synchronous rectification, the LS gate is driven with the inverse of the HS gate.
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