Hello, What I'm missing is if the 74LS02 is a fixed requirement, or if there is an option to use the 3.3V sibling. Thus shifting the problem to the xx74xx02 inputs. Because if you kill the 74LS02 with your experiments it might hurt less than if you kill the BBB.
I would NOT use current limiting resistors, I don't thing that they > solve the problem. > This has been done for decades. I don't see why it should not work for the Sitara. If the I/O voltage is 3.3V and we assume the clamping voltage 0.3V the overvoltage is 5V-3.6V = 1.4V. As an indication of clamping diode capability can we take the pin current capability. Eg. 4mA (varies over pins). Than we would only need a 350Ohm series resistor. -> Take 10k and you cover all the wrong assumptions ;-). You can take even higher resistors (eg. 100k). But you will limit your maximum frequency because somewhere you will not charge the capacity of the Sitara input buffers fast enough. High resistors values can also increase EMC susceptibility. Further more pins USB0_VBUS and USB1_VBUS should withstand 5V. But I assume you need USB and you need 4 inputs. Chilli -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
