Overview

This document contains general layout recommendations for all Apollo4 devices. Please see the Apollo4 and Apollo4 Blue datasheets for recommendations and guidelines for component selections and subsystem design considerations.

Power

• Decoupling capacitors, such as those for VDDP, VDDA and VDDH, should be as close as possible to their respective pins.
• For power rails that connect to inner balls of the packages, the decoupling capacitor should ideally be placed on the opposite side of the Apollo4, directly under the pin, with a via to connect them.
• For the buck inductors (SIMO Buck and BLE Buck), it is recommended to have solid ground underneath the traces and inductors.
• SIMO and BLE buck traces should be as thick and as short as possible. In the event that it is not possible to minimize both trace lengths, SIMOBUCK_SW and VDDBH_SW should be prioritized for the shortest trace length, as these are the switch nodes of the buck converters.
• If using BLE and/or Audio, VDDAUDA should be routed in such a way to minimize its exposure to high frequency and noisy signals, such as MSPI clock signals or buck converter outputs. It is recommended to have it shielded with ground.

Oscillators

• Oscillator traces and components should be shielded as much as possible with ground.
• Maintain a solid ground plane on the layer adjacent to the oscillator circuitry, avoiding routing other signals directly underneath the crystal and capacitors.

MIPI

• The MIPI clock and data signals should be impedance matched to 50-ohm +/- 15% single-ended, 100-ohm +/- 15% differential.
• MIPI clock and data trace pairs should be trace-length matched as closely as possible.
• Maintain a solid ground reference for the MIPI traces, avoid routing over any discontinuities in the plane.
• Minimize via use as much as possible.

USB Signals

• The USB signals should be impedance matched to 50-ohm +/- 15% single-ended, 90-ohm +/- 15% differential.
• The USB trace pair should be trace-length matched as closely as possible, and should not exceed 50 mils in trace length difference.
• Maintain a solid ground reference for the USB traces, avoid routing over any discontinuities in the plane.
• Minimize via use as much as possible.

Radio

• The RFIOP trace connecting to the matching network and antenna should be impedance controlled to 50-ohms.
• Maintain a solid ground plane beneath and next to the matching components and traces leading to the antenna.

MSPI

• MSPI signals should be impedance matched to 50-ohms +/- 20%.
• MSPI Data signals should be trace-length matched to within +/- 250-mils of the Clock signal.
• MSPI signals should be referenced to a solid plane (VDD or GND).
• MSPI signals should not be routed over any discontinuities in the reference plane.

eMMC

• eMMC signals should be impedance matched to 50-ohms +/- 15%.
• eMMC data and CMD signals should be trace-length matched to within +/- 250-mils of the clock signal.
• eMMC signals should be referenced to a solid plane (VDD or GND).
• eMMC signals should not be routed over any discontinuities in the reference plane.

Audio

• LPADC positive and negative signals should be routed differentially, with ground surrounding and shielding the traces on the adjacent layer.
• Match the routing of the LPADC channels as closely as possible.