• Status: Draft / corrected architecture selected; schematic capture may proceed after final part/pinout sourcing.
• Device: Left-ear prototype of a custom BLE hearing-device/IEM system with an over-ear electronics hook and an in-ear multi-driver body.
• Goal: Personal hearing correction, BLE audio/control, onboard recording, per-ear DSP, and prototype validation.

• R&D prototype for bench and acoustic-coupler validation before any in-ear use.
• Not production-intent and not medically certified.
• Must include hearing-safety limits before wearable testing.

• Capture ambient audio through two hook microphones.
• Run BLE audio/control and high-level audio handling on the nRF5340.
• Use a Cirrus Logic CS47L63 audio DSP/front-end to bridge the nRF5340 stereo I2S stream into a multichannel downstream audio stream.
• Use the CS47L63 onboard DSP to share hearing-correction / filtering load where practical.
• Store profiles and recordings in external QSPI flash.
• Communicate with a phone over BLE / BLE Audio.
• Recharge from USB-C and support firmware update/debug access.
• Drive a multi-BA in-ear acoustic assembly through one downstream digital Class-D amp per BA branch.

• nRF5340-CLAA-R BLE SoC, WLCSP95.
• Cirrus Logic CS47L63-CWZR audio DSP/front-end, WLCSP61.
• Three Analog Devices / Maxim MAX98360AEFB+ mono digital-input Class-D amplifiers, one per BA branch.
• nPM1100 PMIC/charger concept.
• W25Q01JV 1 Gbit QSPI NOR flash concept.
• 32 MHz crystal and 2.4 GHz chip antenna concept.
• Hook microphones: 2× TDK InvenSense ICS-40730 analog differential MEMS microphones, 74 dB SNR target.
• USB-C charging and firmware access.
• SWD test pads for recovery/debug.
• Removable 3.7 V 150 mAh LiPo prototype battery via JST-PH.
• Triple balanced-armature IEM concept: WBFK woofer, CI mid, TWFK dual tweeter.

Diagram

• USB-C provides 5 V input.
• LiPo battery is removable for v0.1 prototyping.
• Reverse-polarity protection is mandatory before the PMIC battery input.
• PMIC rail current capability must be validated against SoC, flash, mics, CS47L63, and three MAX98360A audio amps.
• Add USB-C CC pull-downs, ESD, VBUS protection, and no-backfeed safeguards.

• nRF5340 handles BLE, storage control, USB DFU strategy, system control, and host-side audio streaming.
• CS47L63 handles audio front-end / DSP duties and expands the nRF5340 stereo I2S interface into the downstream multichannel audio path.
• WLCSP + chip antenna is high RF/assembly risk for first revision; reference layout or module should be considered.

• Hook microphones are specified as 2× TDK InvenSense ICS-40730 analog differential MEMS microphones.
• The ICS-40730 is not currently available in the Flux library and will require part creation/import or substitution before exact schematic capture.
• Earlier PDM hook-mic assumptions are superseded by the ICS-40730 analog-differential mic decision.
• Whether the IEM body still needs a local reference/feedback microphone remains an open system requirement unless explicitly removed.

• Previous MAX98306 architecture is rejected.
• Corrected path: nRF5340 stereo I2S into CS47L63; CS47L63 routes/processes audio and emits a multichannel digital ASP/TDM stream to three MAX98360A mono amplifiers.
• The MAX98360A is a digital PCM/I2S/TDM input amplifier. It must not be driven from the CS47L63 analog OUTP/OUTN headphone output.
• The CS47L63 analog output is mono differential OUTP/OUTN and is not the three-channel BA drive path.
• MAX98360A TDM mode requires an 8-channel frame with 16-bit or 32-bit slots. Three amps can select different slots using DAI configuration plus GAIN_SLOT strapping.

• User decision: 7 conductors.
• If CS47L63 and the three MAX98360A amps are in the IEM body, a 7-conductor flex can carry the hook-to-IEM digital/control link as: 3V0, GND, I2S_BCLK, I2S_FSYNC/LRCLK, I2S_DOUT, I2C_SCL, I2C_SDA.
• This leaves no spare conductor for reset, interrupt, MCLK, shield, or extra ground; schematic capture must verify CS47L63 clocking/reset strategy before finalizing the connector pinout.
• If the CS47L63 remains in the hook instead of the IEM body, the 7-conductor flex must be revisited because the downstream multichannel TDM or amplifier signals would cross the flex.

• USB-C: VBUS, GND, D+, D-, CC1, CC2, shield strategy.
• Battery: BAT+, BAT-, protected LiPo requirement, polarity marking.
• SWD: SWDIO, SWDCLK, GND, optional VREF/VCC, 100 ohm series resistors.
• Flash: QSPI SCK, CS, IO0-IO3, power, ground, hold/write-protect biasing as required.
• CS47L63 control: I2C preferred for 7-conductor flex economy; SPI would require more conductors unless colocated with nRF5340.
• nRF5340 to CS47L63 audio: stereo I2S / ASP link.
• CS47L63 to MAX98360A amps: local 8-slot TDM digital audio bus with one slot selected per amp.

• Battery: 3.7 V nominal, 150 mAh pouch cell prototype.
• Runtime target is not yet validated; full power budget is required before PMIC/regulator commitment.
• Charge current must be conservative for 150 mAh cell and thermal limits.
• Audio output must be disabled or limited during USB attach/DFU unless validated.

• Initial power tree is conceptual only.
• Required next step: current budget for nRF5340 active/radio/DSP, CS47L63, three MAX98360A amps at expected SPL, flash read/write/erase, microphones, PMIC losses, USB charging, and sleep mode.

• Found in Flux library: CS47L63-CWZR, MAX98360AEFB+T / MAX98360AEFB+, NRF5340-CLAA-R7, NPM1100-QDAA-R7, W25Q01JVZEIQ, USB4125-GF-A, SPH0641LM4H-1, BAT54 variants.
• Not found in Flux library: TDK InvenSense ICS-40730, Knowles WBFK-30095-000, Knowles CI-22955-000, Knowles TWFK-30017-000, exact 32 MHz 2.0×1.6 mm crystal, exact 7-pin 0.5 mm FFC/FPC connector.
• A 7-pin exact flex connector may need a specific MPN; the library has similar 0.5 mm FFC/FPC connectors at higher pin counts.

• Prototype v0.1 left ear only.
• Rigid-flex PCB is expected eventually, but first electrical prototype may benefit from a larger rigid validation board.
• WLCSP assembly and RF tuning are high risk.
• Include test pads for power rails, SWD, USB, I2S/TDM/flex, I2C, mic outputs, and audio outputs.

• Boot/DFU entry button on GPIO P0.11 concept.
• USB DFU behavior must be validated for nRF5340 and PMIC port-detect timing.
• SWD recovery pads are mandatory.
• Zephyr / nRF Connect SDK support exists for CS47L63 in the nRF5340 Audio DK ecosystem, but custom routing to three MAX98360A amps may require devicetree/driver/audio-routing work.
• Firmware must implement hard output gain limits, startup mute, watchdog/mute policy, and no full-scale audio test defaults.

• Over-ear hook module contains battery, USB-C, SoC, PMIC, antenna, flash, hook microphones, and debug pads.
• IEM body should contain CS47L63, three MAX98360A amps, acoustic drivers, and any local reference microphone if retained, so the 7-conductor flex carries only power, I2C, and nRF-to-CS47L63 audio.
• Antenna keepout and battery/enclosure proximity must be defined before PCB layout.

• CS47L63 audio front-end selected to resolve nRF5340 native multichannel/TDM limitation.
• Use CS47L63 digital ASP/TDM output, not its analog headphone output, to feed MAX98360A amps.
• Keep flex cable at 7 conductors only if CS47L63 and amps are located in the IEM body and I2C control is acceptable.
• Add battery reverse-polarity protection for prototype safety.
• Add hearing-safety constraints before any in-ear test.

• Current project is left-ear prototype only.
• User-provided component list is a concept BOM, not yet fully validated.
• The uploaded images are treated as v0.1 architecture sketches, not final schematics.
• CS47L63 will be placed on the IEM-side electronics if the 7-conductor flex remains fixed.

• 2026-07-15: Requirements extracted from uploaded concept text/images. Architecture review found blocking issues in audio amp compatibility and flex conductor count.
• 2026-07-16: Updated architecture to nRF5340 → CS47L63 → 3× MAX98360A → three BA branches; retained 7-conductor flex and 2× ICS-40730 hook microphones; added sourcing status and digital-TDM-only constraint for MAX98360A.