Layout is critical for good power-supply design.
Section 10.2 shows the recommended PCB-layout
configuration. A list of PCB layout considerations
using these devices is listed as follows:
- As with any switching regulator, several power or
signal paths exist that conduct fast switching
voltages or currents. Minimize the loop area
formed by these paths and their bypass
- 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.
- The AVIN bypass capacitor should be placed close
to the AVIN pin and provide a low-impedance path
to PGND at the thermal pad.
- Keep signal components local
to the device, and place them as close as possible
to the pins to which they 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 10.2.
- The PGND pins must be directly connected 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 should 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, and VDD5