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July 25, 2006
News - According to Pete - Febru…
about 4 years ago
Yes, but most chips have ESD diodes, which is why your absolute maximum ratings are what they are, usually -0.3V to VDD+0.3V.
This means that the (say) 9V going into your hi-Z pin gets clamped to VDD+0.3V (ESD diode forward voltage), and your LED turns on. And you cannot turn it off, because the ESD diodes are always going to be there.
If you need to drive LEDs from a higher voltage, use an external NPN/NMOS transistor.
As for why pulling LEDs low (as opposed to driving them high) is so common, some chips still have higher sinking capability than sourcing, because NMOSes are just plain better than PMOSes. Did some quick googling and found a DAC board specced at 8 mA sink and only 0.4mA source, which proves the point beautifully. Yes, I imagine it had a NMOS and a pullup as opposed to a full half bridge output, but hey.
News - New Products Extravaganza…
about 6 years ago
Well, you could just use a small micro and some relays, or if you don’t want to get into micros, a flip-flop. You’d want a toggle (T) flip-flop, but personally I just build ‘em out of a JK flip-flop, as finding T flip-flops is problematic.
In either case, it won’t affect the sound quality in any way. And you don’t have to deal with flaky switches causing scratching noises and other mess if you use relays and some logic - just debounce the switches with a resistor and capacitor.
about 6 years ago
No, the thermal design is completely different. The one in the datasheet is correct; the top copper pour is connected directly to the thermal vias.
On this PCB, there is a thermal relief around the thermal pad - look for the dark corners around it. These increase the thermal resistance.
Hrrm. It looks like you have a thermal relief on the thermal pad of the LED - isn’t this a bit disingenious?
Seems a bit pointless given the otherwise thorough thermal design, what with all the vias dotted around it and all.
News - Infrastructure Woes
about 7 years ago
Poor guys. I couldn’t live without my 30/30 Mbps connection ($110/month) - let’s hope that fiber gets more widespread in a speedy manner. Sure, I don’t have any fancy SLAs, but ~6 hours downtime per year doesn’t really bother me that much.
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