abse/museair-usb

validation/esp-regulator-heat-design.json

{
  "revision": "0.5.7",
  "scope": "Replace only ESP supply U2 and its support circuit to reduce 5V-to-3.3V conversion heat",
  "regulator": {
    "part": "AP63203WU-7",
    "jlcpcb": "C780769",
    "topology": "fixed 3.3V synchronous buck",
    "reference_input_range_v": [
      3.8,
      32
    ],
    "reference_current_rating_a": 2,
    "pin_map": {
      "1": "FB -> V3V3",
      "2": "EN -> USB5V",
      "3": "VIN -> USB5V",
      "4": "GND",
      "5": "SW -> ESP_SW",
      "6": "BST -> ESP_BST"
    }
  },
  "support": {
    "L1": "SWPA4030S4R7MT C57269, 4.7uH \u00b120%, shielded 4x4mm",
    "C2": "Existing 10uF input capacitor, moved close to VIN",
    "C3": "Existing 22uF output capacitor, moved close to inductor",
    "C11": "Existing imported C14663 capacitor type, 100nF between BST and SW",
    "C12": "Existing imported C45783 capacitor type, additional 22uF at output"
  },
  "inductor_rating_signoff": {
    "status": "Nominal prototype current margins confirmed from JLCPCB catalog; manufacturer PDF unavailable",
    "source": "https://jlcpcb.com/partdetail/C57269",
    "checked_at_utc": "2026-10-09T19:25:02.298941+00:00",
    "manufacturer_part": "SWPA4030S4R7MT",
    "inductance_uH": 4.7,
    "tolerance_percent": 20,
    "rated_current_A": 2,
    "saturation_current_A": 3.2,
    "DCR_ohm": 0.078,
    "intended_ESP_rail_max_A": 0.6,
    "minimum_design_rating_A": 1,
    "minimum_design_saturation_A": 1.2,
    "catalog_margins_pass": true,
    "manufacturer_pdf_reviewed": false,
    "whole_converter_2A_rating_claimed": false,
    "physical_rail_current_and_ripple_measured": false
  },
  "reference_design": {
    "source": "https://github.com/sparkfun/Buck_Regulator_AP63203",
    "commit": "63cdc8eadd1258e32630f4e8ce2c1978d6ed62a5",
    "verified": "Pinout, fixed-output FB connection, bootstrap capacitor, 4.7uH inductor, 10uF input and 2x22uF output"
  },
  "heat_estimate": {
    "input_v": 5,
    "output_v": 3.3,
    "sustained_output_a": 0.3,
    "old_ldo_loss_w": 0.51,
    "assumed_buck_efficiency": 0.9,
    "buck_conversion_loss_w": 0.11,
    "estimated_reduction_percent": 78.43,
    "measured": false,
    "scope": "Total converter loss estimate; allocation between IC and coil is not characterized"
  },
  "preserved": [
    "U4 sensor regulator and sensor rail components",
    "J3 sensor pin map",
    "J6 programming pin map",
    "USB-C pin mapping",
    "boot, reset and GPIO connections",
    "board dimensions and carrier holes"
  ],
  "unrelated_review_findings_changed": false,
  "hardware_tested": false,
  "manufacturer_pdf_fetch": "Direct manufacturer/distributor downloads blocked by environment; reference design and exact imports used, remaining ratings signoff documented"
}