I'm working on an AVR/JTAG/whatever programmer. The programmer will interface with chips running at various voltage levels, ranging from 1.8V to 5V. The programmer runs at 3.3V.
The programmer interfaces with the programee through four 3-state pins, which I control from the 3.3V chip, and I need those pins to provide logic levels supplied by the user. I've tried the following (VDD is the user-supplied voltage), but unfortunately, with R1 = 220, the switching was too slow; I'd like to communicate at up to 10MHz.
I've looked at voltage-translator ICs, but the best that I found was SN74LVC8T245, which won't however allow me to tristate each pin separately.
What should I use to perform the voltage translation?