Layout is critical for good power-supply design.
Section 1 shows the recommended PCB-layout configuration. A list of PCB layout
considerations using these devices is listed as follows:
Minimize the loop area formed
by power or signal paths and the bypass connections. As with any switching
regulator, several power or signal paths exist that conduct fast switching
voltages or currents.
Bypass the PVIN pins to PGND
with a low-impedance path. Place the input bypass capacitors of the
power-stage as close as physically possible to the PVIN and PGND pins. A
high-frequency bypass capacitor is integrated to reduce switching spikes and
EMI. Additional EMI bypass capacitor can be placed on the other side of the
PCB directly underneath the device to keep a minimum loop.
Keep signal components local to the device, and place them
as close as possible to the pins to which the signal components are
connected. These components include the VOSNS and GOSNS series resistors and
differential filter capacitor as well as MSEL1, MSEL2, VSEL, and ADRSEL
resistors. Those components can be terminated to AGND with a minimum return
loop or bypassed to the copper area of a separate low-impedance analog
ground (AGND) that is isolated from fast switching voltages and current
paths and has single connection to PGND on the thermal pad through the AGND
pin. For placement recommendations, see Section 8.5.2.
Connect the PGND pins
directly to the thermal pad of the device on the PCB, with a low-noise,
low-impedance path.
Route the VOSNS and GOSNS
lines from the output capacitor bank at the load back to the device pins as
a tightly coupled differential pair. These traces must be kept away from
switching or noisy areas which can add differential-mode noise.
Use caution when routing of
the SYNC, VSHARE, BCX_CLK, and BCX_DAT traces for stackable configurations.
The SYNC trace carries a rail-to-rail signal and must be routed away from
sensitive analog signals, including the VSHARE, VOSNS, and GOSNS signals.
The VSHARE traces must also be kept away from fast switching voltages or
currents formed by the PVIN, AVIN, SW, a