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pico-led-matrix/pcb/LedArrayMux
History
radex 2f9fe494e4
pcb: update errata 		2024-04-14 11:45:42 +02:00
..
LedArrayMux.kicad_pcb pcb: mux design 2024-04-06 22:22:09 +02:00
LedArrayMux.kicad_pro pcb: mux design 2024-04-06 22:22:09 +02:00
LedArrayMux.kicad_sch pcb: mux design 2024-04-06 22:22:09 +02:00
README.md pcb: update errata 2024-04-14 11:45:42 +02:00

README.md

LED Multiplexer

50x50mm module for driving rows and columns of LED Matrix modules

Revisions

Rev A

Manufactured 2024-04-06, delivered 2024-04-13.

Errata:

  1. PMOS gates are pulled up to VLED (5V), while the shift register is powered from 3V3 and signals above VCC are not allowed. Ouch!
    • NMOS gates (i.e. row drivers) are not affected
    • This is not easily fixable on the board itself
    • It doesn't appear that 74HC595 dies immediately because of this, and the 10k resistor would limit worst-case scenario current to 0.5mA, but probably bad idea to ignore this altogether
    • It's possible to set VCC to 5V, and add level shifting on signal lines
    • Alternatively, the shift register could be replaced with 74HCT595 so that 3V3 signals register as logic high at 5V VCC