Datasheet

L6920DC Detailed description
9/16
The maximum load current is defined by the following relationship:
Equation 1
Where η is the efficiency and I
LIM
is the current limit.
Of course, if I
LOAD
is greater than I
LOAD_LIM
the regulation is lost (Figure 8).
Figure 8. No regulation C2 = V
out
; C3 = Inductor Current
5.2 Start-up
One of the key features of L6920DC is the startup at supply voltage down to 0.8V (please
see the diagram in Figure 4).
The device leaves the startup mode of operation as soon as Vout goes over 1.4V. During
startup, the synchronous switch is off and the energy is transferred to the load through its
intrinsic body diode.
The N-channel switches with a very low R
DS(on)
thanks to an internal charge pump used to
bias the power MOS gate. Because of this modified behavior, T
ON
/T
OFF
times are
lengthened. Current limit and zero crossing detection are still available.
I
LOAD_LIM
V
in
V
out
-----------
I
LIM
T
OFF_MIN
V
out
V
in
–
2L⋅
-------------------------
⋅–
⎝⎠
⎛⎞
η⋅⋅=