project
12 V to 5 V / 1 A Buck Molecule (TPS54202)
Public Unreviewedby John Lauer
An independently designed 12 V to 5 V, 1 A synchronous buck molecule (TI TPS54202), with calculations, ngspice and PSpice simulation, KiCad 10 schematic and board, and the board laid out and analysed with adom-aiflow.
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scaffold/probe-plan.jsondeleted−109@@ -1,109 +0,0 @@-{- "frame": "molecule: mm from the centre of MP1 (front-left machine pin), x right, y up; scaffold: layout mm (molecule FL pin at 260, 488, rotation 0)",- "points": [- {- "ref": "TP1",- "net": "SW",- "molecule": {- "x": 15.6,- "y": 4.9- },- "layout": {- "x": 275.6,- "y": 492.9- },- "measure": "switch node: 500 kHz square wave, 0 V to VIN, check ringing on the edges",- "expect": "500 kHz, 0 to 12 V at VIN 12 V",- "ground": "TP4"- },- {- "ref": "TP2",- "net": "FB",- "molecule": {- "x": 9.4,- "y": 5.6- },- "layout": {- "x": 269.4,- "y": 493.6- },- "measure": "feedback node: DC only, high impedance, use a 10x probe",- "expect": "0.596 V (datasheet reference)",- "ground": "TP4"- },- {- "ref": "TP3",- "net": "VOUT",- "molecule": {- "x": 21.6,- "y": 4.9- },- "layout": {- "x": 281.6,- "y": 492.9- },- "measure": "output DC and ripple; ripple with the probe's ground spring on TP4, not a lead",- "expect": "4.98 V DC (4.86 to 5.11 V over tolerances); about 3 mV pp at 12 V, 1 A (ngspice 3.17 mV; TI model 5 mV)",- "ground": "TP4"- },- {- "ref": "TP4",- "net": "GND",- "molecule": {- "x": 15.6,- "y": 2.8- },- "layout": {- "x": 275.6,- "y": 490.8- },- "measure": "probe ground next to SW and VOUT",- "expect": "0 V",- "ground": null- }- ],- "tests": [- {- "name": "power up",- "setup": "PS1 12.0 V, current limit 0.8 A, EN released (USER_IO25 input), no load on VOUT",- "check": "VMON on USER_IO29 (ADC3) reads 2.49 V (VOUT/2); TP3 4.98 V; LED D1 on",- "source": "design/calcs.json"- },- {- "name": "soft start",- "setup": "as above, then pull EN low for 100 ms and release; scope TP3 and TP1",- "check": "VOUT rises in about 5 ms (95 % at 4.8 ms), overshoot under 5 mV",- "source": "sim/transient_12V.json and the TI model"- },- {- "name": "ripple at 1 A",- "setup": "5 Ohm load (or electronic load 1.0 A) on J4/J5; scope TP3 AC-coupled with a ground spring to TP4, 20 MHz bandwidth limit",- "check": "about 3 to 5 mV pp",- "source": "ngspice 3.17 mV, TI model 5.0 mV"- },- {- "name": "load step",- "setup": "electronic load 0 to 1 A and 0.5 to 1 A steps, 1 A/us; scope TP3",- "check": "0.5 A steps: 80 to 95 mV; full 1 A step about 185 mV (3.7 %), settling about 0.2 ms",- "source": "TI PSpice model (93 / 91 mV per 0.5 A at 1 A); the fitted ngspice model says 78 / 77 mV"- },- {- "name": "UVLO",- "setup": "no load; sweep PS1 up from 5 V then down, watching VMON",- "check": "starts at 8.58 V, stops at 6.87 V",- "source": "design/calcs.json (EN 1 M / 150 k)"- },- {- "name": "input range",- "setup": "1 A load; PS1 at 9, 12 and 16 V",- "check": "VOUT 4.98 V at each; PS1 current about 0.6 A at 9 V, 0.45 A at 12 V",- "source": "design/calcs.json efficiency estimate 93 %"- },- {- "name": "thermal",- "setup": "1 A load, 12 V, still air, 10 minutes; thermal camera",- "check": "U1 and L1 rise about 40 to 45 C above ambient (Fields: U1 GND pin +44 C, L1 +41 C)",- "source": "aiflow/spec.json hotMaxRiseNote"- }- ]-}