Datasheet

Evaluation Board User Guide UG-205
Rev. A | Page 3 of 12
COMPONENT DESIGN
For information about selecting power components and
calculating component values, see the ADP1850 data sheet.
INDUCTOR SELECTION
A 0.47 μH inductor with a 50 A saturation current rating and a
30 A average current rating (744355147 from Würth Elektronik)
is selected. This is a compact inductor with an iron alloy core,
which offers high performance in terms of low R
DC
and low core
loss. An alternative to the 744355147 is the SER1408-301M
(300 nH with about 40 A in saturation current and average
current rating) from Coilcraft. If higher efficiency or lower
DCR is desired, choose a physically larger inductor with
approximately the same inductance value.
INPUT CAPACITORS
Because of the large input current ripple requirement, four
180 μF/16 V OS-CON™ capacitors have been selected for the
input bulk capacitance. In addition, one MLCC decoupling
capacitor (10 μF/25 V) is used at each of the high-side MOSFET.
OUTPUT CAPACITORS
A total of six 560 μF/2.5 V OS-CON™ capacitors is used at
the output. These aluminum solid capacitors with conductive
polymer have low ESR and high current ripple rating. In
addition, four 47 μF MLCCs are added for filtering out the
high frequency voltage ripples.
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. As 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.
For the high-side MOSFETs of each channel, two BSC080N03LS
connected in parallel from Infineon Technologies in the PG-
TDSON-8 or Super-SO8 package are selected. This part has
low input capacitance (1.2 nF) and fast transition time (3 ns).
For the low-side MOSFET, two BSC030N03LS connected in
parallel, with R
DSON
of 4.7 mΩ at a V
GS
of 4.5 V, are selected.