a5974ad STMicroelectronics, a5974ad Datasheet - Page 37

• Manufacturer Part Number: a5974ad
• Description: Up To 2 A Step-down Switching Regulator For Automotive Applications
• Manufacturer: STMicroelectronics

A5974AD
8.7
Figure 25. Positive buck-boost regulator
Negative buck-boost regulator
In
voltage is:
Equation 38
where the ideal duty cycle D for the buck-boost converter is:
Equation 39
The considerations given in
Equation 35
considering the conversion V
Equation 40
Equation 41
An important point to take into account is that the ground pin of the device is connected to
the negative output voltage. Therefore, the device is subjected to a voltage equal to V
which must be lower than 36 V (the maximum operating input voltage).
10V
Figure
26, the schematic circuit for a standard buck-boost topology is shown. The output
to
4.7
6.8
37
can be used to calculate the maximum output current. So, for example,
A5974AD
Section 8.7
IN
Doc ID 018762 Rev 1
I
SW
= 12 V to V
=
V
D
I
-------------- -
1 D
LOAD
OUT
D
–
=
for the real duty cycle are still valid here. Also
=
--------------- -
5
=
OUT
+
----------------------------- -
V
=
5
IN
12
–
–
----------------------- -
1 0.706
V
V
–
= -5 V, I
–
IN
OUT
=
V
0.5
⋅
OUT
0.706
------------ -
1 D
D
–
LOAD
=
1.7A
= 0.5 A:
Application information
ESR>35m
470
AM09690v1
IN
Ω
37/49
-V
6
O
,