Phase current control
L6472
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DocID022729 Rev 5
7.3
Auto-adjusted fast decay during the falling steps
When the target current is decreased by a microstep change (falling step), the device
performs a fast decay in order to reach the new value as fast as possible. Anyway,
exceeding the fast duration may cause a strong ripple on the step change. The L6472
device automatically adjusts these fast decays reducing the current ripple.
At reset, the fast decay value (t
FALL
) is set to FALL_STEP/4 (T_FAST register). The t
FALL
value is doubled every time, within the same falling step, an extra fast decay is necessary to
obtain an ON time greater than TON_MIN. The maximum t
FALL
value is equal to
FALL_STEP.
At the next falling step, the system uses the last t
FALL
value of the previous falling step.
Stopping the motor or reaching the current sine wave zero crossing causes the current
control system to return to the reset state.
Figure 17. Adaptive decay switch from normal to slow + fast decay mode and vice-versa