a5975d STMicroelectronics, a5975d Datasheet - Page 38

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

Application information
8.8
38/50
The switch peak current must be lower than the minimum current limit of the overcurrent
protection (see
DC current of the device.
As a consequence, the maximum output current is:
Equation 37
where I
The current capability is reduced by the term (1-D) and so, for example, with a duty cycle of
0.5, and considering an average current through the switch of 3 A, the maximum output
current deliverable to the load is 1.5 A.
Figure 26
5 V input.
Figure 26. 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
10V
Figure
SW MAX
27, the circuit schematic for a standard buck-boost topology is shown. The output
below shows the schematic circuit of this topology for a 12 V output voltage and
to
4.7
6.8
37
represents the rated current of the device.
Table 4
can be used to calculate the maximum output current. So, for example,
for details) while the average current must be lower than the rated
A5975D
Section 8.8
IN
Doc ID 018760 Rev 1
= 12 V to V
I
OUT MAX
V
OUT
D
for the real duty cycle are still valid here. Also
=
≅
=
OUT
----------------------------- -
V
I
SW MAX
IN
–
–
V
V
–
= -5 V, I
IN
OUT
V
⋅
OUT
------------ -
1 D
⋅
(
D
–
1 D
–
LOAD
)
= 0.5 A:
ESR>35m
470
A5975D
AM09693v1
Ω
6