Bob1 wrote:I have not determined which route to pursue. At this time I am experimenting with pull-up resistors on a working system, which has with a few “2.4 volt chips” installed.
It’s difficult to judge the effects of pull-up resistors while looking at a data signal with a scope, but I don’t think a 3.3K contributes to a measurable change on the high levels. Some are between 3.5 and 4 volts. Others are very near 5 volts.
For non-compliant inputs, a series resistor to limit the injection current into the input of the memory device may be possible, but this might introduce operating speed limitations. The injection current would need to be limited to a quite low value - check the specification for the memory device, and keep well below the maximum limit for a single input (consider how many input lines may simultaneously have injection current). A 4k7 series resistor should limit the current to about 0.4mA.
For the address bus and other unidirectional control lines you may well be able to us a suitable voltage divider to halve the voltage ouput from the MCU (perhaps a pair of 4k7 resistors for each input).
Regards,
Mac
Bob1 wrote:
but what if someday they begin to live down (so to speak) to their worse case specification?
I need to determine if this is a valid concern.
Regards,
Bob