From 2f9fe494e4a11d7cec8b0c136b5805ead5e8e4d6 Mon Sep 17 00:00:00 2001 From: radex Date: Sun, 14 Apr 2024 11:45:42 +0200 Subject: [PATCH] pcb: update errata --- pcb/DemoBoard1/README.md | 2 +- pcb/LedArray/README.md | 2 +- pcb/LedArrayMux/README.md | 17 ++++++++++++++++- 3 files changed, 18 insertions(+), 3 deletions(-) diff --git a/pcb/DemoBoard1/README.md b/pcb/DemoBoard1/README.md index f9c6700..8d60bb6 100644 --- a/pcb/DemoBoard1/README.md +++ b/pcb/DemoBoard1/README.md @@ -1,4 +1,4 @@ -# Demo Baord 1 +# Demo Board 1 Learning how to use shift registers, darlington arrays, and mosfets. I don't know what I'm doing. diff --git a/pcb/LedArray/README.md b/pcb/LedArray/README.md index 6f5dd66..196b597 100644 --- a/pcb/LedArray/README.md +++ b/pcb/LedArray/README.md @@ -7,7 +7,7 @@ ### Rev A 1. I'm an idiot and somehow managed to switch polarity of LEDs. Rows were supposed to be cathodes, and columns anodes, but it's the other way around. Fixable by a 90° rotation, albeit with less than ideal trace layout. Oh well. -2. The notes about the XL-1608SURC-06 LED are incorrect, and were in fact taken from XL-1608SURC-04's data sheet. The correct info is: +2. The notes about the XL-1608SURC-06 LED are incorrect, and were in fact taken from XL-1608SURC-04's data sheet. (Correction: It seems that the ealier version of XL-1608SURC-06 datasheet was incorrect). The correct info is: - Forward voltage: 1.9-2.3V (at 20mA) - Max peak forward current: 80mA - Max continuous forward current: 20mA diff --git a/pcb/LedArrayMux/README.md b/pcb/LedArrayMux/README.md index 1989d4e..4f510ed 100644 --- a/pcb/LedArrayMux/README.md +++ b/pcb/LedArrayMux/README.md @@ -1,3 +1,18 @@ -# LED Multiplexer - WIP +# 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