PI33XX-X1 Datasheet, PDF (23/26 Pages) Vicor Corporation – 8V to 36Vin, 15A Cool-Power ZVS Buck Regulator

Layout Guidelines
To optimize maximum efficiency and low noise
performance from a PI33XX-X1 design, layout
considerations are necessary. Reducing trace
resistance and minimizing high current loop returns
along with proper component placement will
contribute to optimized performance.
A typical buck converter circuit is shown in Figure 9.
The potential areas of high parasitic inductance and
resistance are the circuit return paths, shown as LR
below.
PI33XX-X1
When Q1 is on and Q2 is off, the majority of CIN’s
current is used to satisfy the output load and to
recharge the COUT capacitors. When Q1 is off and
Q2 is on, the load current is supplied by the inductor
and the COUT capacitor as shown in Figure 11.
During this period CIN is also being recharged by the
VIN. Minimizing CIN loop inductance is important to
reduce peak voltage excursions when Q1 turns off.
Also, the difference in area between the CIN loop
and COUT loop is vital to minimize switching and
GND noise.
Figure 9 - Typical Buck Converter
The path between the COUT and CIN capacitors is of
particular importance since the AC currents are
flowing through both of them when Q1 is turned on.
Figure 10, schematically, shows the reduced trace
length between input and output capacitors. The
shorter path lessens the effects that copper trace
parasitics can have on the PI33XX-X1 performance.
Figure 11 - Current flow: Q2 closed
The recommended component placement, shown in
Figure 12, illustrates the tight path between CIN and
COUT (and VIN and VOUT) for the high AC return
current. This optimized layout is used on the PI33XX-
X1 evaluation board.
Figure 10 - Current flow: Q1 closed
vicorpower.com
800 735.6200
Figure 12 - Recommended component
placement and metal routing
Rev 1.3
09/2015
Cool-Power^®
Page 23 of 26