Datasheet
Table Of Contents
- Figure 1. Application circuit
- 1 Pin settings
- 2 Maximum ratings
- 3 Electrical characteristics
- 4 Functional description
- 5 Application information
- 5.1 Input capacitor selection
- 5.2 Inductor selection
- 5.3 Output capacitor selection
- 5.4 Compensation network
- 5.5 Thermal considerations
- 5.6 Layout considerations
- 5.7 Application circuit
- Figure 18. Demonstration board application circuit
- Table 9. Component list
- Figure 19. PCB layout (component side)
- Figure 20. PCB layout (bottom side)
- Figure 21. PCB layout (front side)
- Figure 22. Junction temperature vs output current
- Figure 23. Junction temperature vs output current
- Figure 24. Junction temperature vs output current
- Figure 25. Efficiency vs output current
- Figure 26. Efficiency vs output current
- Figure 27. Efficiency vs output current
- Figure 28. Load regulation
- Figure 29. Line regulation
- Figure 30. Short circuit behavior
- Figure 31. Load transient: from 0.1 A to 0.7 A
- Figure 32. Soft-start
- 6 Application ideas
- 7 Package mechanical data
- 8 Order codes
- 9 Revision history

L5980 Application ideas
Doc ID 13003 Rev 6 35/42
Equation 32
where I
SW
is the average current in the embedded power MOSFET in the ON time.
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 Equation 32, also the peak
current in the power MOSFET has to be calculated. The peak current, showed in Equation
33, must be lower than the minimum current limit (1.0 A)
Equation 33
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 Figure 34 the maximum output current for the above configuration is depicted varying the
input voltage from 2.9 V to 18 V.
The dashed line considers a more accurate estimation of the duty cycles given by Equation
34, where power losses across diodes, external power MOSFET, internal power MOSFET
are taken into account.
I
SW
I
OUT
1D–
-------------
0.7 A<=
I
SW,PK
I
OUT
1D–
-------------
1
r
2
---+ 1.0A<⋅=
r
V
OUT
I
OUT
LF
SW
⋅⋅
------------------------------------
1D–()
2
⋅=