mirror of https://github.com/radex/radmatrix.git
pcb: update errata
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# Demo Baord 1
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# Demo Board 1
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Learning how to use shift registers, darlington arrays, and mosfets. I don't know what I'm doing.
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Learning how to use shift registers, darlington arrays, and mosfets. I don't know what I'm doing.
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### Rev A
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### Rev A
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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.
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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.
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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:
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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:
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- Forward voltage: 1.9-2.3V (at 20mA)
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- Forward voltage: 1.9-2.3V (at 20mA)
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- Max peak forward current: 80mA
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- Max peak forward current: 80mA
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- Max continuous forward current: 20mA
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- Max continuous forward current: 20mA
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# LED Multiplexer - WIP
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# LED Multiplexer
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50x50mm module for driving rows and columns of LED Matrix modules
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50x50mm module for driving rows and columns of LED Matrix modules
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## Revisions
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### Rev A
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Manufactured 2024-04-06, delivered 2024-04-13.
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Errata:
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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!
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- NMOS gates (i.e. row drivers) are not affected
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- This is not easily fixable on the board itself
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- 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
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- It's possible to set VCC to 5V, and add level shifting on signal lines
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- Alternatively, the shift register could be replaced with 74HCT595 so that 3V3 signals register as logic high at 5V VCC
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