EN2390QI
Layout Recommendation
Figure 15: Cri t i cal Com ponent Lay out for Mi ni m um
Footprint (Top Layer). See F igure 14 for s chemati c .
Thi s l ayout onl y s hows t he cri t i cal com ponents and top
layer traces for minimum footprint in single-supply,
master mode with ENABLE tied to AV IN. Alt ernate circui t
configurations & other low-
connected and routed according to custom er applicatio n.
P l ease see t he Gerber fil es at www.altera.com/enpirion
f or detail s on al l l ayers .
Recommendation 1: Input and output filter
capacitors should be placed on the same side of
the PCB, and as close to the EN2390QI package
as possible. They should be connected to the
device with very short and wide traces. Do not use
thermal reliefs or spokes when connecting the
capacitor pads to the respectiv e nodes. The +V a n d
GND traces between the capacitors and the
EN2390QI should be as close to each other as
possible so that the gap between the two nodes is
minimized, even under the capacitors.
Re comme ndation 2: The PGND connections for
the input and output capacitors on layer 1 need to
have a slit between them in order to provide some
separation betw een input and output current loops.
Recommendation 3: The system ground plane
should be the first layer immediately below the
surface layer. This ground plane should be
conti nuous and un-interrupted below the converter
and the input/output capacitors.
Recommendation 4: The therm al pad underneath
the component must be connected to the system
ground plane through as many vias as possible.
The drill diameter of the vias should be 0.33mm,
and the vi as m ust have at least 1 oz. copper plating
on the inside wall, making the finished hole size
around 0.20-0.26mm. Do not use thermal reliefs or
spokes to connect the vias to the ground plane.
This connection provides the path for heat
dissipation from the converter.
Recommendation 5: M ultiple small vias (the same
size as the thermal vias discussed in
recommendation 4) should be used to connect
ground terminal of the input capacitor and output
capacitors to the system ground plane. It is
preferred to put these vias along the edge of the
G ND c o pper closest to the +V copper. T hese vias
connect the input/output filter capacitors to the
GND plane, and help reduce parasitic inductances
in the input and output curre nt loops. If vias cannot
be placed under the capacitor s, then place them on
both si des of the slit in the top layer PGND copper.
Recommendation 6: AVIN is the power supply for
the small-signal control circuits. AVINO powers
AVIN in single supply mode. AVIN and AVINO
should have a decoupling capacitor close to each
of their pins. Refer to F igure 15.
Recommendation 7: The layer 1 metal under the
device must not be more than shown in Figure13.
Refer to the section regarding Exposed Metal on
Bottom of Package. As with any switch-mode
DC/DC converter, try not to run sensitive signal or
control lines underneath the converter package on
other layers.
Recommendation 8: The VOUT sense point should
be just after the last output filter capacitor . Keep t he
sense trace short in order to avoid noise coupling
into the node. Contact Altera MySupport for any
remote sensing applications.
Recommendation 9: Keep RA, CA, RB, and RCA
close to the V FB pin (Refer to Figure 15). The VFB
pin is a high-impedance, sensitive node. Keep the
trace to this pin as short as possible. Whenever
possible, connect RB directly to the AGND instead
of going through the GND plane.
Recommendation 10: Follow all the layout
recommendations as close as possible to optimize
performance. Altera pr ovides schematic and layout
reviews for all customer designs. Contact Altera
MySupport
(www.altera.com/mysupport).
www.altera.com/enpirion Page 23