L6235 STMicroelectronics, L6235 Datasheet - Page 10

• Manufacturer Part Number: L6235
• Description: DMOS DRIVER FOR THREE-PHASE BRUSHLESS DC MOTOR
• Manufacturer: STMicroelectronics

L6235
Figure 8. Output Current Regulation Waveforms
Figure 9 shows the magnitude of the Off Time t
culated 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
10/25
t
t
20K
0.47nF
t
t
t
t



RCFALL
OFF
DT
OFF(MIN)
OFF(MAX)
RCRISE
t
t
R
V
ON
OFF
ON
V
SENSE
SENSE
I
= 1µs (typical value)
OUT
V
REF
2.5V
OFF
V
= t
ON
5V
REF
0
RC
RCRISE
and C
RCFALL
t
t
= 600 · C
= 0.6 · R
R
ON MI N
RCRISE
= 6.6µs
RCRISE
C
OFF
= 6ms
SYNCHRONOUS RECTIFICATION
OFF
D02IN1351
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
OFF
100nF
DT
=
t
DT
1.5 s (typ. value)
= 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.
ON(MIN)
+ t
OFF
Slow Decay
t
DT
RCFALL
ON
1 s t
t
versus C
1 s t
t
RCRISE
OFF
, which depends by motors and supply parameters, has to
C
.
BLANK
DT
OFF
D
DT
and R
RCRISE
t
ON
is the internally generated Dead Time with:
A
OFF
B
of the voltage at the pin RCOFF. The
values. It can be approximately cal-
Slow Decay
t
RCFALL
1 s t
t
1 s t
t
RCRISE
OFF
C
BLANK
DT
D
ON