STMicroelectronics Stepper motor driver mounting the L6474 in high power PowerSO package EVAL6474PD EVAL6474PD Ficha De Dados
Códigos do produto
EVAL6474PD
L6474
Phase current control
Doc ID 022529 Rev 3
29/52
7.3
Auto-adjusted fast decay during the falling steps
When the target current is decreased by a micro-step 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 could cause a strong ripple on the step change. The L6474
automatically adjusts these fast decays reducing the current ripple.
performs a fast decay in order to reach the new value as fast as possible. Anyway,
exceeding the fast duration could cause a strong ripple on the step change. The L6474
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
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 sinewave zero crossing causes the current
control system to return to the reset state.
control system to return to the reset state.
Figure 11.
Adaptive decay - switch from normal to slow+fast decay mode and vice
versa
versa
Time
Time
reference current
1
st
fast decay
Target current is increased (raising step)
2
nd
fast decay
system returns to slow decay mode and t
FAST
value is halved
switch to fast + slow decay mode
t
FAST
t
OFF,FAST
t
OFF,SLOW
t
OFF
t
OFF
reference current