Phase current control
L6482
38/73
Doc ID 023768 Rev 1
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. However,
exceeding the fast duration could cause a strong ripple on the step change. The L6482
automatically adjusts these fast decays reducing the current ripple.
At reset the fast decay value (tFALL) is set to FALL_STEP/4 (T_FAST register). The tFALL
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 (see
). The maximum tFALL value is
equal to FALL_STEP.
At the next falling step, the system uses the last tFALL 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.
Figure 20.
Adaptive decay - switch from normal to slow+fast decay mode and vice
versa
Time
Time
reference c
u
rrent
1
s
t
f
as
t dec
a
y
T
a
rget c
u
rrent i
s
incre
as
ed (r
a
i
s
ing
s
tep)
2
nd
f
as
t dec
a
y
s
y
s
tem ret
u
rn
s
to
s
low dec
a
y mode
a
nd t
FA
S
T
v
au
le i
s
h
a
lved
s
witch to f
as
t +
s
low dec
a
y mode
t
FA
S
T
t
OFF,FA
S
T
t
OFF,
S
LOW
t
OFF
t
OFF
reference c
u
rrent
AM15051v1
