ADC CS5381KKSZ 4-layer PCB diagram.
This project is a custom-designed, high-precision Analog-to-Digital Conversion (ADC) board optimized for professional audio and precision instrumentation. It utilizes a fully differential signal chain to maximize dynamic range and minimize common-mode noise, making it suitable for high-EMI environments.
- ADC: CS5381K-KSZ (120dB Dynamic Range, 24-bit, 192kHz sampling). A flagship Delta-Sigma converter.
- Front-End Driver: ADA4940-2 Ultra-low noise, fully differential amplifier.
- Sensors: 2x ICS-40730 Bottom-Port MEMS Microphones with 74dB SNR for high-definition acoustic capture.
To leverage the 120dB SNR of the CS5381, I implemented a fully differential path from the amplifier to the ADC.
- The Challenge: Converting single-ended sensor signals while maintaining a -122dB SFDR.
- The Solution: Used the ADA4940-2 to provide a stable common-mode voltage and high linearity, ensuring the ADC inputs stay within the optimal swing range.
In high-speed mixed-signal design, phase coherency between channels is critical.
- Via Propagation Delay: One of my analog traces required two vias (unavoidable). To prevent phase shift, I calculated the vertical travel distance through the 1.6mm PCB stackup and compensated the "via-free" traces by adding 3.2mm of serpentine meanders.
- Tolerance: Achieved sub-0.5mm effective electrical length matching across all high-priority analog traces.
- Copper Pours: Utilized large 3.3V and 5V copper polygons on the top layer to minimize IR drop and loop inductance.
- Isolation: Strategically distanced power pours from high-speed digital lines to prevent capacitive crosstalk.
Unlike traditional "Split Plane" designs, this board utilizes a Solid Ground Plane strategy on internal layers 2 and 3 to ensure the lowest possible impedance for return currents.
- Low-Inductance Return Paths: By maintaining a continuous ground plane under the analog and digital sections, I minimized the loop area for high-speed I2S signals, preventing ground-bounce and radiated emissions.
- Component Partitioning: Rather than a physical split in the copper, I used Spatial Isolation. Analog components (ADA4940, CS5381 input stage) are physically grouped on one side of the board, while digital I/O and the STM32 interface are on the opposite side, ensuring digital return currents do not traverse the sensitive analog "quiet zone."
- Layer Stackup:
- Layer 1: Signal / Power Pours
- Layer 2: GND (Solid Reference)
- Layer 3: GND (Solid Reference)
- Layer 4: Signal / Power Pours
I am an Engineering Graduate from the University of British Columbia (UBC). I specialize in the intersection of Embedded Systems and Data Engineering. Whether it's designing 6-DoF robotic arms or high-fidelity ADC boards, I focus on "First Principles" engineering—calculating via delays, optimizing power pours, and ensuring data integrity from the sensor to the report.