Diagram

• Status: Resolved by removing MAX98306 from the architecture.
• Replacement architecture uses CS47L63 plus three MAX98360A digital-input mono Class-D amps.

• Status: Resolved conceptually by the CS47L63.
• CS47L63 provides two audio serial ports. Datasheet evidence: ASP1 supports up to eight input/output channels; ASP2 supports up to four input/output channels; I2S and TDM modes are supported.
• nRF5340 can send stereo I2S to CS47L63, and the CS47L63 can emit a multichannel digital stream for the downstream amps.

• Status: Resolved if the MAX98360A amps are driven from a CS47L63 digital ASP/TDM output.
• MAX98360A TDM mode accepts 8 channels only, with 16-bit or 32-bit slots and exactly 128 or 256 BCLK cycles per frame.
• Three amps can select different TDM slots using DAI configuration plus GAIN_SLOT strapping.

• CS47L63 analog output: mono differential OUTP/OUTN headphone/earpiece path.
• MAX98360A input: digital PCM/I2S/TDM only; no analog input.
• Therefore the valid path is: CS47L63 ASP_DOUT + BCLK + FSYNC to MAX98360A DAI pins.
• Invalid path: CS47L63 OUTP/OUTN analog output into MAX98360A.

• Flex cable pin count remains 7 conductors.

• No spare conductor for CS47L63 RESET, IRQ, MCLK, amplifier enable, cable detect, shield, or extra ground.
• I2C is strongly preferred over SPI because SPI control would consume too many conductors.
• CS47L63 clocking/reset/interrupt requirements must be checked during schematic capture.
• If CS47L63 is placed in the hook instead of the IEM body, the 7-conductor flex becomes insufficient again for a robust multichannel downstream audio/power/control interface.

• User decision: 2× TDK InvenSense ICS-40730 analog differential MEMS microphones, 74 dB SNR target.
• These are independent of the downstream amp architecture.
• Flux library status: not currently found; requires part creation/import, user-supplied library, or substitution.

• The previous concept included an IEM-body SPH0641LM4H-1 PDM reference microphone.
• The latest user correction only explicitly resolves the hook microphones, so the IEM reference/feedback mic remains an open requirement unless removed.

• Nordic/Zephyr ecosystem support exists for CS47L63, but custom routing from stereo I2S input to three downstream MAX98360A slot outputs may require nontrivial codec/DSP configuration.
• Schematic should include test pads on ASP/I2S/TDM signals for bring-up.

• MAX98360A is intended for small speaker loads and can deliver far more energy than safe for high-sensitivity balanced-armature receivers.
• Hardware and firmware SPL limiting, startup mute, per-amp gain/slot validation, and acoustic-coupler testing are mandatory.

• The nPM1100 rail capacity must be validated with nRF5340, CS47L63, flash, two analog mics, and three Class-D amps.
• A 150 mAh LiPo plus three amps may impose runtime and thermal limits.

• nRF5340 WLCSP plus chip antenna requires strict Nordic RF layout and tuning.
• Ear, skin, battery, flex, and enclosure will detune the antenna.
• Consider a certified module or larger validation board for first electrical prototype if schedule/risk matters.

• ICS-40730 and Knowles BA receiver parts are absent from the Flux library.
• Exact schematic capture for those devices requires importing/creating parts from datasheets or selecting library-available substitutes.

1. Add available core ICs: nRF5340, CS47L63, MAX98360A ×3, nPM1100, W25Q01JV, USB-C, SWD/test pads.
2. Source or create the missing ICS-40730 and BA receiver parts from datasheets before placing those exact devices.
3. Finalize CS47L63 placement in the IEM body if the 7-conductor flex remains fixed.
4. Use I2C control across the flex; avoid SPI across the 7-conductor flex.
5. Verify CS47L63 clocking/reset/IRQ requirements and whether any signal requires an eighth conductor.
6. Add hearing-safety limits and test pads before layout.

• MAX98306 is not an I2S/3-channel amp.
• nRF5340 cannot natively generate the required multichannel MAX98360A TDM stream.
• A four-conductor flex is insufficient for the original mixed I2S/PDM plan.