ShiboSoftwareDev/f1c100s-linux-gameboy

POWER-REVISION.md

# Power correction, revision 1.9.1

- U_2V5: Diodes AP2112K-2.5TRG1, SOT-25, JLCPCB C176945. Replaces U_1V8 without changing its pin mapping or placement. Input pin 1 and enable pin 3 receive 3.3 V, pin 2 is ground, pin 4 is unconnected, pin 5 supplies DDR1 at 2.5 V.
- U_2V8: Diodes AP2127K-2.8TRG1, SOT-23-5; same 1=IN, 2=GND, 3=EN, 4=NC, 5=OUT mapping. Supplies only codec AVCC and its decoupling/bulk capacitor. Input/output capacitors are 4.7 µF 0805 X7R, 16 V. JLCPCB C460327; exact manufacturer part verified in jlcsearch.
- 3.3 V I/O/USB/headphone/TV and 1.2 V core supplies retained. JP_BOOT recovery arrangement retained.

Datasheet limits: DDR1 2.3–2.7 V (nominal 2.5); codec AVCC 2.5–3.1 V (nominal 2.8). AP2112 2.5 V ±2% gives 2.45–2.55 V; AP2127 2.8 V ±2% gives 2.744–2.856 V before load/transient effects.

Sources:
- Allwinner F1C100S datasheet, section 5.2: https://linux-sunxi.org/images/b/ba/F1C100s_Datasheet_V1.0.pdf
- AP2112: https://www.diodes.com/datasheet/download/AP2112.pdf
- AP2127, sections pin descriptions, electrical characteristics, package outline: https://www.diodes.com/datasheet/download/AP2127.pdf
- DRAM assembly part: https://jlcpcb.com/partdetail/DiodesIncorporated-AP2112K_25TRG1/C176945

The repaired prior board ran Linux using an external 2.5 V supply. That validates the diagnosis, not this unbuilt revision. Before production, prototype and measure startup order (Allwinner section 5.5), rail transients, core tolerance (nominal 1.2 V is the recommended upper bound), regulator temperatures, USB integrity and the fabricator's final stackup. Peripheral load budget and existing inventory shortages still apply.