AVR-Chat

kernels_nz wrote:
> Hi Again ! I ended up using the resistor method in my design - main
> problem was not the cost of adding 14 resistors, but rather that id
> already designed the PCB and it was a pain in the A to add 14
> resistors to the tightly packed Nordic RF circuit. Managed to fit them
> in using 0603 resistors. By the way, 1k5 and 1k give 5V to 3V. 
> 
> I believe it will work fine, as the fastest data rate is only in the
> 100s of kHz 
> 
> I was only hoping someone would say something like : "Oh on, don't use
> resistors, the simplest way that takes zero space is . . . " didn't
> get the answer I was hoping for unfortunately. 
> 
> Reminds me of my uni electronics lecturer's favorite quote: "Theres no
> free lunch in electronics"

If the data rate isn't too fast and the latchup current of overdriven
inputs is specified, you can use a single series resistor between output
and input. Even if the latchup current isn't specified, you can still gain
some confidence by abusing a chip with 10-20mA overdrive and see if it's
tolerant.