Rev A Locked Architecture Details

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cigz75

Run AD5940 datasheet limits review only.
Do not modify schematic wiring. Do not add components. Do not change nets.
Review the AD5940 placeholder against datasheet/application-circuit requirements and identify what must be locked before PCB layout.
Check:
  1. Rail requirements:
  • AVDD valid voltage range
  • DVDD valid voltage range
  • IOVDD / digital I/O rail requirement
  • REG_1V8 role
  • whether DVDD_AD5940 may remain tied to MCU_3V3: yes/no/uncertain
  • whether separate 1.8 V rail placeholder is required: yes/no/uncertain
  1. SPI/logic compatibility:
  • whether STM32L552 3.3 V SPI can directly connect to AD5940: yes/no/uncertain
  • whether level shifting may be required: yes/no/uncertain
  1. BioZ/EIS pins:
  • map placeholder nets to likely AD5940 pins/functions: AD5940_I_PLUS_PATH AD5940_I_MINUS_PATH AD5940_V_PLUS_PATH AD5940_V_MINUS_PATH AD5940_CURRENT_SENSE_P AD5940_CURRENT_SENSE_N AD5940_EXC_MON AD5940_AIN_MON
  1. Application-circuit blockers:
  • required external references
  • required RTIA/RLOAD/RCAL components
  • required clock/crystal if any
  • required decoupling not already represented
  • required reset/interrupt/control pins
  1. Pre-layout decision: Choose one: A. Keep AD5940 as placeholder only B. Add separate 1.8 V LDO placeholder C. Add level-shifter placeholder only D. Split DVDD_AD5940 from MCU_3V3 E. Need human datasheet review before schematic changes
Report only:
  • AD5940 rail blockers
  • SPI/logic blockers
  • missing application-circuit components
  • recommended next schematic action
  • whether current AD5940 section is safe for PCB layout: yes/no

flux

I’ll run a read-only AD5940 datasheet-limits review against the current placeholder section, check rails, SPI logic, pin-role mapping, and application-circuit gaps, then report only the blockers and next action.

flux

C

cigz75

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Schematic

Layout

Preview

Firmware and Data Export Plan
EchoS Bank Rev A firmware plan:
MCU: STM32L552 placeholder controller.
Host connection: USB-C to Mac/laptop using USB device mode.
Data export:
  • Stream raw complex impedance data to Mac.
  • Export frequency, magnitude, phase, real impedance, imaginary impedance, timestamp, mux state, calibration state, and temperature.
  • Save CSV-compatible records.
  • Preserve raw data; do not only export processed results.
Per-measurement metadata:
  • selected I+ electrode/channel
  • selected I- electrode/channel
  • selected V+ electrode/channel
  • selected V- electrode/channel
  • mux address state IN0-IN15
  • mux enable state
  • frequency
  • excitation amplitude
  • AD5940 gain/state
  • calibration ID
  • board temperature
  • analog-region temperature
Rules:
  • Do not modify schematic wiring.
  • Do not add components.
  • Do not modify USB.
  • Do not modify AD5940, MCU, muxes, electrode dock, or calibration bank.