Recommended Values
for Paralleled DC-DC Converters
The capacitance value used (Cout) should
be approximately 1µF per parallel channel
(i.e. for 2 parallel single output converters,
2µF between the common positive output
and OV).
The same comments can be applied to the
input circuit for converters whose inputs are
paralleled, and similar values for inductance
and input capacitance should be used as
shown above.

In general, paralleling of converters should
only be done when essential, and a higher
power single converter is always a prefera-
ble solution. There should always be a cor-
rection factor of the maximum power rating
to allow for mismatch between converters,
and a selection at full load test is recom-
mended, to ensure the output voltage is
matched to within 1% or 2%. In general a
factor of 0.9 should be used to provide a
power safety margin per converter (e.g. 2
C/D converters paralleled should only be
used up to a power level of 3.6W, not their
4W maximum). At most three DC-DC con-
verters can be paralleled with a high level of
confidence in the overall performance. If the
circuit needs more power than three con-
verters in parallel, then a single converter
with a much higher power rating should be
considered.

Regulated output DC-DC converters should
not be paralleled, since their output voltage
would need to be very accurately matched,
to ensure even loading (to within the tole-
rance of the internal linear regulator). Pa-
ralleling regulated converters could cause
one of the parts to be overloaded. If a high
power regulated supply is required, it would
be better to parallel unregulated converters
and add an external linear regulator.