Quote:
Originally Posted by MPaulHolmes
Hey Squiggles!
On pg. 265 of the ATMega8 datasheet, it has a graph called:
Figure 149. I/O Pin Sink Current vs. Output Voltage (VCC = 5V)
The current will be 5v / 10K for the pulldown, plus 5v / 1K for the PWM series resistor. That makes 5.5mA, which makes for approximately 0.2v. 0.2v + 0.7v is safely under for the HC74 family to be considered low. I see what you mean, though.
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Actually you mean 5v / (10k + 1k) = 4.55mA + the uA feeding gate inputs, when the Output pin is high.
I believe the graph on P265 is showing you how much current an output pin can sink at a particular voltage. So a max of 30mA at 0.7V 25DegC
The table on page 242 shows that an output pin can be a max of 0.7V when the output is set low. Way back in my schooling days this was the figure we designed too.