ESP32-S3 Audio Hardware Optimization

I am looking for an expert Electronics Design Engineer to review, optimize, and finalize a draft KiCad schematic for a custom, battery-powered audio logging device. The core architecture relies on an ESP32-S3-WROOM-1-N16R8-1U module paired with a TDK T5838 digital microphone featuring Acoustic Activity Detection (AAD). The device operates primarily in an ultra-low power standby mode: the ESP32-S3 stays in deep sleep with Wi-Fi completely turned off, while the TDK T5838 remains always-on to monitor the acoustic environment. When a sound trigger occurs, the microphone must wake the ESP32-S3 using an AAD interrupt (via D1, D2, or Analog AAD mode) to record audio onto a microSD card. The ESP32-S3 will wake up its Wi-Fi radio only during a specific, firmware-defined time window to transmit the recorded files. The system is powered by a 3.7V LiPo/Li-ion battery (capacities ranging from 2,500 mAh up to 10,000 mAh). There is also a 5V external input available for future deployment. Scope of Work & Deliverables 1. Power Entry Stage & Cold-Swap Protection • Remove Charging Circuit: Completely strip out the existing 3.7V battery charging subsystem. • Mechanical Footprint Update: Replace the current Surface Mount Technology (SMT) JST-PH 2.0mm battery connector with a robust, Through-Hole (THT) Right-Angle JST-PH variant to handle repeated structural stress during manual swaps. • Cold-Swap Mitigation: Design a protection stage (e.g., TVS diodes and adequate bulk capacitance) to absorb inrush current spikes, contact bounce, and voltage arcs caused by manual battery hot/cold swaps. • Reverse Polarity Protection: Implement a zero-loss or ultra-low-loss reverse polarity protection circuit (e.g., an appropriately rated P-Channel MOSFET or a dedicated ideal diode IC). Traditional silicon/Schottky diodes are unacceptable due to their forward voltage drop and wasted battery capacity. 2. Ultra-Low Power Optimization & Power Gating • Always-On vs. Gated Rails: Keep the TDK T5838 microphone and the ESP32-S3 RTC domain on an ultra-low quiescent current (\(I_{q}\)) always-on rail. • Peripheral Isolation: Implement load switches (e.g., low-leakage P-channel MOSFETs or dedicated load switch ICs like the TPS22917) to completely cut off power to the microSD card and its associated pull-up resistors when the system is asleep. • Component Benchmarking: Review the active Bill of Materials (BOM) and replace inefficient components (such as old AMS1117 LDOs) with ultra-low \(I_{q}\) voltage regulators (e.g., high-efficiency Buck-Boost regulators or nano-amp LDOs like the TPS7A02). 3. Signal Integrity, Impedance & Back-Current Prevention • Back-Current & Leakage Auditing: Ensure no digital lines or pull-up resistors leak parasitic current into unpowered peripherals or back-feed the ESP32-S3 pins during deep sleep. • Signal Validation: Confirm clean signal paths between the TDK T5838 (AAD D1/D2/Analog pins) and the ESP32-S3 RTC GPIOs, as well as the microSD SDIO/SPI lines. • Impedance/Resistance Checks: Verify that pull-up/pull-down values are optimized for low consumption while preserving edge-rate signal integrity. 4. Fuel Gauge / Battery Monitoring • Add a programmable, low-overhead circuit to monitor and read remaining battery capacity/voltage via firmware (e.g., using a high-impedance voltage divider switched via a MOSFET, or a dedicated ultra-low-power I²C fuel gauge IC). 5. Interface Overhaul (USB-C & 5V Input) • Replace 2-Pin 5V Connector: Replace the existing vertical 2-pin connector with an elegant, low-profile, sink-only USB Type-C connector for the 5V input. • USB-C Logic & OTG Functionality: Ensure CC1/CC2 lines are properly terminated with 5.1kΩ resistors so standard USB-C PD power bricks can power the board. The Native USB OTG lines of the ESP32-S3 must maintain flawless connectivity to a PC for flashing firmware and debugging. • Power Muxing: Ensure safe isolation between the 5V USB-C input and the 3.7V raw battery rail so they never back-feed or damage each other. Layout Consultation (Optional but Welcomed) • Provide a brief set of high-level recommendations or placement notes for the physical PCB layout (especially regarding audio signal traces, ground planes, and USB differential pairs), which I will be routing myself. Required Skills • High proficiency in KiCad Schematic Capture • Deep expertise in Ultra-Low Power (Micro-amp/Nano-amp) hardware design • Strong background with ESP32-S3 SoC systems and peripheral power management • If you read this sentence then message me with "Hello-World". And one important thing: If you are using some AI tool to generate the schema or to check the required above requirements then you are the wrong person for this job. • Experience with Digital Microphones (I2S/PDM/AAD) and high-speed data buses (microSD/SDIO) Regards, Sergiu