TPA3255EVM: Power ON sequence for TPA3255EVM

• Pop Noise: Without reset, power-up transients may produce audible pops through speakers, especially if inputs are active or capacitors are pre-charged.
• Fault Triggering: Rapid PVDD ramp or inrush current to speaker loads (4–8 Ω) could trigger a fault, forcing the device into shutdown (FAULT pin low).

Datasheet Guidance : The TPA3255EVM user guide advises connecting PVDD (set to 51 V, 10 A), speakers (4–8 Ω), and inputs (RCA jacks) before powering up, with RESET low to avoid issues. After power is stable, switch RESET to ON. Bypassing reset assumes stable conditions, which may not always hold in noisy automotive environments.                     

• Preferred Approach: Follow the datasheet and start with RESET switch OFF (low). After PVDD (e.g., 48–51 V) is stable and all connections are verified, toggle RESET to ON. This ensures clean startup and minimizes pop noise or faults.
• If Leaving ON:
  • Verify all connections (PVDD, GND, speakers, inputs) are secure and within specs (e.g., 4–8 Ω loads, 14–53.5 V PVDD).
  • Ensure PVDD ramp is controlled (e.g., <100 ms rise time) to avoid inrush triggering OCP or UVLO.
  • Mute audio inputs (e.g., set to 0 V or disconnect) during power-up to reduce pop noise risk.
  • Monitor FAULT and CLIP_OTW pins for issues (low indicates fault or thermal warning).
• Mitigate Risks:
  • Add an RC delay (e.g., 10 kΩ + 1 µF) on the RESET pin to automatically hold it low briefly during power-up if manual switching isn’t feasible.
  • Test for pop noise with speakers connected; if present, use an external mute circuit or follow reset sequence.
  • In your EV charger context, ensure EMI from GaN FETs (e.g., LMG3522R030) doesn’t interfere with TPA3255 control signals. Use filtering (e.g., ferrite beads) if needed.