Datasheet

Application ideas L5980
36/42 Doc ID 13003 Rev 6
Figure 34. Maximum output current according to max DC switch current (0.7 A):
V
O
=12V
Equation 34
where V
D
is the voltage drop across diodes, V
SW
and V
SWE
across the internal and external
power MOSFET.
6.2 Inverting buck-boost
The L5980 can implement the step up/down converter with a negative output voltage.
Figure 33 shows the schematic to regulate -5 V: no further external components are added
to the standard buck topology.
The relationship between input and output voltage is:
Equation 35
So the duty cycle is:
Equation 36
D
V
OUT
2V
D
⋅+
V
IN
V
SW
V
SWE
V
OUT
2V⋅
D
++––
------------------------------------------------------------------------------------------- -=
V
OUT
V
IN
–
D
1D–
-------------
⋅=
D
V
OUT
V
OUT
V
IN
–
----------------------------- -=