a5975d STMicroelectronics, a5975d Datasheet - Page 32

• Manufacturer Part Number: a5975d
• Description: Up To 3 A Step-down Switching Regulator For Automotive Applications
• Manufacturer: STMicroelectronics

Application information
8.4
8.5
32/50
RMS current of the embedded power MOSFET
As the A5975D embeds the high side switch, the internal power dissipation is sometimes
the bottleneck for the output current capability (refer to
operating temperature).
Nevertheless, as mentioned in the general description
continuous output current of 3 A in most of the application conditions.
However, the rated maximum RMS current of the power elements is 2 A, where:
and the real duty cycle D:
Fixing the limit of 2 A for I
in
Figure 18. Maximum continuous output current vs. duty cycle
Short-circuit protection
In overcurrent protection mode, when the peak current reaches the current limit, the device
reduces the T
frequency to approximately one third of its nominal value even when synchronized to an
external signal (see
strongly reduced and, in most applications, this is enough to limit the current to I
event, in case of heavy short-circuit at the output (V
application conditions (V
peak could reach values higher than I
Figure
18.
ON
down to its minimum value (approximately 250 nsec) and the switching
Section 5.4: Current
CC
RMS HS
D
value and parasitic effect of external components), the current
=
Doc ID 018760 Rev 1
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V
IN
V
, the maximum output current can be derived, as illustrated
OUT
+
I
(
RMS HS
R
+
LIM
DS (on) LS
(
R
.
protection). In these conditions, the duty cycle is
DS (on) LS
=
I
LOAD
–
R
DS (on) HS
+
O
⋅
DCR
= 0 V) and depending on the
D
on page
Section 8.3
) I
⋅
) I
⋅
LOAD
LOAD
1, the device can manage a
for the estimation of the
LIM
. In any
A5975D