Datasheet

L6227
10/22
Figure 8. Output Current Regulation Waveforms
Figure 9 shows the magnitude of the Off Time t
OFF
versus C
OFF
and R
OFF
values. It can be approximately cal-
culated from the equations:
t
RCFALL
= 0.6 · R
OFF
· C
OFF
t
OFF
= t
RCFALL
+ t
DT
= 0.6 · R
OFF
· C
OFF
+ t
DT
where R
OFF
and C
OFF
are the external component values and t
DT
is the internally generated Dead Time with:
20K
Ω ≤ R
OFF
≤ 100K Ω
0.47nF ≤ C
OFF
≤ 100nF
t
DT
= 1µs (typical value)
Therefore:
t
OFF(MIN)
= 6.6µs
t
OFF(MAX)
= 6ms
These values allow a sufficient range of t
OFF
to implement the drive circuit for most motors.
The capacitor value chosen for C
OFF
also affects the Rise Time t
RCRISE
of the voltage at the pin RCOFF. The
Rise Time t
RCRISE
will only be an issue if the capacitor is not completely charged before the next time the
monostable is triggered. Therefore, the on time t
ON
, which depends by motors and supply parameters, has to
OFF
BC
DDA
t
ON
t
OFF
BC
ON
2.5V
0
Slow Decay Slow Decay
1µs t
BLANK
t
RCRISE
t
RCRISE
SYNCHRONOUS RECTIFICATION
1µs t
BLANK
5V
V
RC
V
SENSE
V
REF
I
OUT
V
REF
R
SENSE
D02IN1351
t
OFF
1µs t
DT
1µs t
DT
t
RCFALL
t
RCFALL