Each system design and printed circuit
board (PCB) layout is unique. The layout must be carefully reviewed in the context
of a specific PCB design. However, the following guidelines can optimize the device
performance:
- Connect the thermal pad to
ground. Use a via pattern to connect the device thermal pad, which is the area
directly under the device, to the ground planes. This connection helps dissipate
heat from the device.
- Star connect all ground pins to
the board ground plane. Use the same ground between VSS and AVSS to avoid any
potential voltage difference between them.
- The decoupling capacitors for the
power supplies must be placed close to the device pins.
- Route the analog differential
audio signals differentially on the PCB for better noise immunity. Avoid
crossing digital and analog signals to prevent undesirable crosstalk.
- Avoid running high-frequency
clock and control signals near INxx and OUTxx pins where possible.
- The device internal voltage
references must be filtered using external capacitors. Place the filter
capacitors near the VREF pin for good performance.
- Directly tap the MICBIAS pin to avoid common impedance when
routing the biasing or supply traces for multiple microphones to avoid coupling
across microphones.
- Provide a direct connection from
the VREF and MICBIAS external capacitor ground terminal to VSS.
- Place the MICBIAS capacitor (with low equivalent series
resistance) close to the device with minimal trace impedance.
- Use ground planes to provide the
lowest impedance for power and signal current between the device and the
decoupling capacitors. Treat the area directly under the device as a central
ground area for the device, and all device grounds must be connected directly to
that area.