Network cabinet fan controller

{
  "status": "preliminary; frequency tolerance, MLCC bias curves and switching model pending",
  "topology": "buck",
  "VIN": 12,
  "VOUT": 3.3,
  "fsw_kHz": 1100,
  "assumptions": {
    "VIN12_V": [
      11.4,
      12.6
    ],
    "combined_continuous_fan_A": 2.0,
    "each_fan_continuous_A": 1.0,
    "regulator_output_A": 0.6,
    "ambient_C": 40,
    "qualification": "Self-set prototype envelope; actual fans, supply tolerance and start current still require confirmation."
  },
  "buck": {
    "equation": "DS41326 eq 7: deltaIL=Vout*(Vin-Vout)/(Vin*L*fsw)",
    "frequency_basis": "typical only; not a worst-case guarantee",
    "cases": [
      {
        "vin_V": 11.4,
        "inductor_tolerance": -0.3,
        "ripple_pp_A": 0.7807981492192021,
        "peak_A": 0.990399074609601,
        "inductor_rms_A": 0.6409397885022775
      },
      {
        "vin_V": 11.4,
        "inductor_tolerance": 0.3,
        "ripple_pp_A": 0.4204297726564934,
        "peak_A": 0.8102148863282467,
        "inductor_rms_A": 0.6121520231756155
      },
      {
        "vin_V": 12.6,
        "inductor_tolerance": -0.3,
        "ripple_pp_A": 0.8110936682365254,
        "peak_A": 1.0055468341182627,
        "inductor_rms_A": 0.6440673449941255
      },
      {
        "vin_V": 12.6,
        "inductor_tolerance": 0.3,
        "ripple_pp_A": 0.43674274443505207,
        "peak_A": 0.818371372217526,
        "inductor_rms_A": 0.6131030517523585
      }
    ],
    "recommended_values": "DS41326 table 2: 3.9uH, CIN10uF, COUT2x22uF, CBST100nF",
    "c_out_nominal_uF": 44,
    "c_out_screen_effective_uF": 23.76,
    "cap_derating_note": "60% DC-bias retention is an engineering screen, not verified manufacturer guaranteed capacitance."
  },
  "protection": {
    "mosfet_source": "AOS AO4407A rev11.1 March2024 p2, max17mohm at -6V gate; x1.6 hot assumption",
    "continuous_screen_A": 2.2171052631578947,
    "mosfet_hot_W": 0.1337031163434903,
    "mosfet_drop_V": 0.06030526315789474,
    "fuse_A": 4,
    "fuse_continuous_75percent_A": 3.0,
    "fuse_note": "Littelfuse466 standard25% derating at25C; ambient curve and fan starting I2t still require check."
  },
  "logic": {
    "tach_pullup_max_A": 0.00036363636363636367,
    "tach_filter_time_s": 1.0000000000000002e-06,
    "onewire_pullup_max_A": 0.0007736943907156673,
    "reset_RC_nominal_ms": 10,
    "pwm_period_us": 40,
    "pwm_low_resistor_drop_at_5mA_V": 0.16665000000000002,
    "led_max_A": 0.0008264462809917355
  },
  "required_checks": [
    "Regulator frequency min/max and current-limit tolerance",
    "MLCC effective capacitance at bias and temperature",
    "Fan supply tolerance and start/locked-rotor current",
    "Fused source available fault current",
    "Full mated mechanical fit and cable bend",
    "Thermal and transient simulation/bench tests"
  ]
}