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
Application information L5980
28/42 Doc ID 13003 Rev 6
of heat. The R
thJA
measured on the demonstration board described in the following
paragraph is about 60 °C/W.
Figure 16. Switching losses
5.6 Layout considerations
The PC board layout of switching DC/DC regulator is very important to minimize the noise
injected in high impedance nodes and interferences generated by the high switching current
loops.
In a step-down converter the input loop (including the input capacitor, the power MOSFET
and the free wheeling diode) is the most critical one. This is due to the fact that the high
value pulsed current are flowing through it. In order to minimize the EMI, this loop has to be
as short as possible.
The feedback pin (FB) connection to external resistor divider is a high impedance node, so
the interferences can be minimized placing the routing of feedback node as far as possible
from the high current paths. To reduce the pick up noise the resistor divider has to be placed
very close to the device.
To filter the high frequency noise, a small capacitor (100 nF) can be added as close as
possible to the input voltage pin of the device.
Thanks to the exposed pad of the device, the ground plane helps to reduce the thermal
resistance junction to ambient; so a large ground plane enhances the thermal performance
of the converter allowing high power conversion.
In Figure 17 a layout example is shown.