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L6472
Phase current control
70
7
Phase current control
The L6472 performs a new current control technique, named predictive current control,
allowing the device to obtain the target average phase current. This method is described in
detail in
. Furthermore, the L6472 automatically selects the better decay mode in
order to follow the current profile.
Current control algorithm parameters can be programmed by the T_FAST, TON_MIN,
TOFF_MIN and CONFIG registers (see
,
and
for details).
Different current amplitude can be set for acceleration, deceleration and constant speed
phases and when the motor is stopped through the TVAL_ACC, TVAL_DEC, TVAL_RUN
and TVAL_HOLD registers (see
). The output current amplitude can
also be regulated by the ADCIN voltage value (see
Each bridge is driven by an independent control system that shares the control parameters
only with other bridges.
7.1 Predictive
current
control
Unlike a classical peak current control system, that causes the phase current decay when
the target value is reached, this new method keeps the power bridge on for an extra time
after reaching the current threshold.
At each cycle the system measures the time required to reach the target current (t
SENSE
).
After that the power stage is kept in a “predictive” ON state (t
PRED
) for a time equal to the
mean value of t
SENSE
in the last two control cycles (actual one and previous one), as shown
in
Figure 14. Predictive current control
