Datasheet

Evaluation Board User Guide UG-334
Rev. 0 | Page 3 of 16
COMPONENT DESIGN
For information about selecting power components and
calculating component values, see the ADP1876 data sheet.
INDUCTOR SELECTION
A 1.8 µH inductor with an 18 A saturation current rating
(744325180 from Würth Elektronik) is selected. This is a
compact inductor with a ferrite core, which offers high
performance in terms of low R
DC
and low core loss.
INPUT CAPACITORS
Because of the very low ESR and high input current rating of
multilayer ceramic capacitors (MLCCs), two 10 µF MLCCs in
Size 1210 are selected as the input capacitors at the input of each
channel. In addition, a 150 µF bulk OS-CON™ (aluminum solid
capacitor with conductive polymer) capacitor from SANYO is
chosen for filtering out unwanted low frequency noise from the
input power supply.
OUTPUT CAPACITORS
A combination of POSCAP™ polymer capacitors and MLCCs
are selected for the output rails. Polymer capacitors have low
ESR and high current ripple rating. Connecting polymer
capacitors and MLCCs in parallel is very effective in reducing
voltage ripple. Two 330 µF POSCAP capacitors and two 22 µF
MLCCs are selected for each output.
MOSFET SELECTION
For low output or low duty cycle, select a high-side MOSFET
with fast rise and fall times and with low input capacitance to
minimize charging and switching power loss. For the synchronous
rectifier (low-side MOSFET), select a MOSFET with low R
DSON
because the switching speed is not critical and there is no switching
power loss in the low-side MOSFET.
The MOSFET IPD050N03L in PG-TO252-3-11 (DPAK) from
Infineon is chosen for both the high-side and low-side MOSFETs
for a balance between low cost and good efficiency. The R
DSON
of
the IPD050N03L is about 6 mΩ at a V
GS
of 5 V.