Datasheet

V
AVERAGE
Time (s)
V
H
- V
L
= V
RIPPLE
Output Voltage (V)
V
H
V
L
V
REGULATION
t
ON
t
P
R
FB1
R
FB2
C
D
SW
FB
L
C
OUT
V
OUT
D
Time (s)
Discontinuous Conduction Mode (DCM)
Switchnode Voltage
V
IN
V
OUT
I
PEAK
Time (s)
Discontinuous Conduction Mode (DCM)
Inductor Current
I
AVERAGE
Time (s)
DCM-CCM Boundary
Inductor Current
LM2696
www.ti.com SNVS375B –OCTOBER 2005–REVISED APRIL 2013
Figure 23. Modes of Operation
It can be seen that in DCM, whenever the inductor runs dry the SW node will become high impedance. Ringing
will occur as a result of the LC tank circuit formed by the inductor and the parasitic capacitance at the SW node.
Figure 24. Parasitic Tank Circuit at the Switchpin
LINE REGULATION
The LM2696 regulates to the lowest point of the output voltage (V
L
in Figure 25 ). This is to say that the output
voltage may be represented by a waveform that is some average voltage with ripple. The LM2696 will regulate to
the trough of the ripple.
Figure 25. Average Output Voltage and Regulation Point
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