Datasheet

EVAL-ADP1828LC
Rev. 0 | Page 8 of 12
Table 4. Miscellaneous Information
Parameter Comment
Switching Frequency, f
SW
The switching frequency, f
SW
, is set to 600 kHz (Jumper JP2) on the evaluation board. If a different
f
SW
is needed, the compensation and the power components need to be recalculated. If a f
SW
other
than 300 kHz or 600 kHz is desired, a resistor, R13, can be soldered onto the PCB to select any
frequency between 300 kHz and 600 kHz.
Dual Power MOSFETs: Q1A and Q1B
The footprint for the dual power MOSFETs is laid out to fit both the PowerPAK SO-8 and the
standard SO-8 package so that the user can easily replace the on-board PowerPAK with a standard
SO-8 package.
Inductor
The footprint for the inductor is laid out to fit inductors that are smaller or larger than the on-board
inductor, Toko FDV0630.
VREG and V
IN
For input voltages less than 5.5 V, the user can connect Jumper J7 by shorting VREG to V
IN
.
Snubber Circuit
A snubber RC circuit, R
SNUB
and C
SNUB
, is laid out on the evaluation board to help reduce switching
noise and ringing at the SW node. The user can remove this RC snubber or try different RC values
for a particular application. Keep in mind that the RC snubber dissipates power and slightly
reduces the overall efficiency, generally in the range of 0.1% to 0.5%.
Gate Resistors
The dummy 0 Ω gate resistors, R2 and R3, at DH and DL, respectively, are provided on the
evaluation board for reducing overshoot voltage at the drains of the external MOSFETs. The user
can change these 0 Ω resistors to different values (generally in the range of 1 Ω to 5 Ω) to achieve
the desired reduction in overshoot voltage. Keep in mind that the gate resistor dissipates power
and slightly reduces the overall efficiency.
Capacitor C17
A ceramic capacitor, C17, is placed very close to the drain of the high-side MOSFET. This capacitor,
typically 0.1 μF to 1 μF, helps to reduce input impedance during high frequency transients. C17 is
not assembled on the evaluation board. The user can add this capacitor if needed for a particular
application.
Voltage Divider
If a different output voltage other than 1.8 V is desired, the user needs to change the voltage
feedback divider, R7 and R8, and rework the compensation component values and the input and
output capacitances.