L7986TA STMicroelectronics, L7986TA Datasheet - Page 36

• Manufacturer Part Number: L7986TA
• Description: 3A step-down switching regulator
• Manufacturer: STMicroelectronics

Specifications of L7986TA

• Low Dropout Operation: 100% duty cycle

Application ideas
36/43
Equation 38
where I
To chose the right value of the inductor and to manage transient output current, that for short
time can exceed the maximum output current calculated by
current in the power MOSFET has to be calculated. The peak current, showed in
39, must be lower than the minimum current limit (3.7 A).
Equation 39
Where r is defined as the ratio between the inductor current ripple and the inductor DC
current:
So in the buck boost topology the maximum output current depends on the application
conditions (firstly input and output voltage, secondly switching frequency and inductor
value).
In
input voltage from 4.5 V to 38 V.
The dashed line considers a more accurate estimation of the duty cycles given by
40, where power losses across diodes, external power MOSFET, internal power MOSFET
are taken into account.
Figure 34. Maximum output current according to max DC switch current (3.0 A):
Figure 34
SW
is the average current in the embedded power MOSFET in the on time.
the maximum output current for the above configuration is depicted varying the
V
O
=12 V
Doc ID 022098 Rev 1
I
SW,PK
r
=
----------------------------------- -
I
I
OUT
SW
=
V
------------ -
1 D
I
OUT
=
⋅
OUT
–
L F
------------ -
1 D
I
⋅
OUT
–
⋅
SW
1
<
+
⋅
3 A
(
-- -
2
r
1 D
–
<
3.7A
)
2
Equation
38, also the peak
Equation
Equation
L7986TA