Техническая Спецификация для STMicroelectronics Evaluation board for A5970AD EVALA5970AD EVALA5970AD
Модели
EVALA5970AD
DocID14661 Rev 5
27/42
A5970AD
Application information
42
Equation 31
considering that f
SW
has been already reduced to one third of the nominal.
In case a short-circuit at the output is applied and V
IN
= 12 V the inductor current is
controlled in most of the applications (see
). When the application must sustain the
short-circuit condition for an extended period, the external components (mainly the inductor
and diode) must be selected based on this value.
and diode) must be selected based on this value.
In case the V
IN
is very high, it could occur that the ripple current during T
OFF
does not compensate the current increase during T
ON
shows an
example of a power up phase with V
IN
= V
IN MAX
= 36 V where
IL TON
>
IL TOFF
so the
current escalates and the balance between
and
occurs at a current
slightly higher than the current limit. This must be taken into account in particular to avoid
the risk of an abrupt inductor saturation.
the risk of an abrupt inductor saturation.
Figure 15. Short-circuit current V
IN
= 12 V
Figure 16. Short-circuit current V
IN
= 24 V
I
L TOFF
V
D
V
out
DCR
L
I
+
+
–
L
--------------------------------------------------------------- 3 T
SW
V
D
V
out
DCR
L
I
+
+
–
L
--------------------------------------------------------------- 6
s
=