LT3506/LT3506A
U U
W U
APPLICATIO S I FOR ATIO
Single, Low-Ripple 3.2A Output
prevent the two channels from properly sharing current.
If, for example, channel 1 gets started first, it can supply
the load current, while channel 2 never switches enough
current to get its boost capacitor charged. In this case,
channel 1 will supply the load until it reaches current limit,
the output voltage drops, and channel 2 gets started. The
solution is to generate a boost supply generated from
either SW pin that will service both BOOST pins. The low
profile, single output 5V to 3.3V converter shown in the
Typical Applications section shows how to do this.
The LT3506 can generate a single, low-ripple 3.2A output
if the outputs of the two switching regulators are tied
together and share a single output capacitor. By tying the
two FB pins together and the two V pins together, the
C
two channels will share the load current. There are several
advantages to this two-phase buck regulator. Ripple cur-
rents at the input and output are reduced, reducing volt-
age ripple and allowing the use of smaller, less expensive
capacitors. Although two inductors are required, each will
be smaller than the inductor required for a single-phase
regulator. This may be important when there are tight
height restrictions on the circuit. The Typical Applications
section shows circuits with maximum heights of 1.4mm,
1.8mm and 2.1mm.
Other Linear Technology Publications
Application notes 19, 35 and 44 contain more detailed
descriptions and design information for buck regulators
and other switching regulators. The LT1376 data sheet
has a more extensive discussion of output ripple, loop
compensationandstabilitytesting.Designnote100shows
how to generate a dual (+ and –) output supply using a
buck regulator
Thereisonespecialconsiderationregardingthetwophase
circuit. When the difference between the input voltage and
outputvoltageislessthan2.5V,thentheboostcircuitsmay
3506afb
ꢀꢇ
Linear [ Linear ]
