L6228 STMicroelectronics, L6228 Datasheet - Page 12

• Manufacturer Part Number: L6228
• Description: DMOS DRIVER FOR BIPOLAR STEPPER MOTOR
• Manufacturer: STMicroelectronics

L6228
Figure 11. Output Current Regulation Waveforms
Figure 12 shows the magnitude of the Off Time t
calculated from the equations:
where R
Therefore:
These values allow a sufficient range of t
The capacitor value chosen for C
Rise Time t
monostable is triggered. Therefore, the on time t
be bigger than t
can not be smaller than the minimum on time t
12/26
R
V
V
SENSE
I
SENSE
t
t
20K
0.47nF
t
t
t
OUT
RCFALL
OFF
DT
OFF(MIN)
OFF(MAX)
V
REF
2.5V
OFF
V
ON
5V
REF
OFF
0
RC
= 1µs (typical value)
= t
RCRISE
and C
RCFALL
SYNCHRONOUS OR QUASI
SYNCHRONOUS RECTIFICATION
= 0.6 · R
R
D01IN1334
= 6.6µs
C
RCRISE
OFF
= 6ms
OFF
OFF
will only be an issue if the capacitor is not completely charged before the next time the
+ t
100K
OFF
are the external component values and t
for allowing a good current regulation by the PWM stage. Furthermore, the on time t
100nF
DT
= 0.6 · R
· C
OFF
OFF
OFF
also affects the Rise Time t
· C
OFF
OFF
B
to implement the drive circuit for most motors.
Slow Decay
ON(MIN)
+ t
t
ON
RCFALL
DT
OFF
1 s t
1 s t
t
t
RCRISE
, which depends by motors and supply parameters, has to
OFF
C
.
versus C
BLANK
DT
D
OFF
DT
RCRISE
is the internally generated Dead Time with:
t
ON
A
and R
of the voltage at the pin RCOFF. The
B
OFF
Slow Decay
values. It can be approximately
t
RCFALL
1 s t
1 s t
t
t
RCRISE
OFF
C
BLANK
DT
D
ON