MixedSigPCB

Mixed-Signal Audio PCB

A USB-powered mixed-signal board for audio-bandwidth signal generation and analysis. Built around an STM32F1 MCU with a DAC output stage, ADC input, and BNC output — aimed at applications like function generation, frequency-response measurement, DSP prototyping, and general lab/instrumentation use.

Designed in KiCad, fabricated and assembled via JLCPCB (LCSC parts).

Status

🚧 In development. Schematic and layout are largely complete; BOM population (LCSC part numbers) is still outstanding. Not yet fabricated.

• Schematic capture
• PCB layout & routing
• ERC / DRC clean
• BOM with LCSC part numbers
• Fabrication / assembly

Overview

Repository Layout

.
├── *.kicad_pro          # KiCad project file
├── *.kicad_sch          # Schematic
├── *.kicad_pcb          # PCB layout
├── Custom.pretty/       # Custom footprint library
└── README.md

Design Notes

• 4-layer stackup with two inner ground plane for return-current management and decoupling.
• Regulator: TLV62569 buck with a right-sized 6.8 µH inductor (XRNR3015 series) — inductance chosen deliberately for PFM light-load behaviour and loop stability, not just DC current rating.
• Decoupling: GND vias placed directly at cap pads into the inner plane to minimise loop inductance and avoid tight-clearance top-layer routing.
• Crystal: 3225 4-pad SMD; load caps sized per ST AN2867, accounting for PCB stray capacitance.
• Custom footprints: Custom.pretty contains the common-mode choke, USBLC6-2SC6, XRNR3015 inductor, and a USB-C SMT footprint. Verify all against manufacturer datasheets before ordering.

Toolchain

• EDA: KiCad
• Fabrication / Assembly: JLCPCB (4-layer)
• Component sourcing: LCSC

References

• STMicroelectronics AN2867 — crystal oscillator design guidelines
• TLV62569 datasheet
• Manufacturer datasheets for all custom-footprint parts

License

(Choose one — e.g. CERN-OHL-S for hardware, MIT/GPL for any firmware. Add a LICENSE file.)

Author: Otsile · University of Cape Town