I need recommendations for level shifters for 2 shifting scenarios. I have used the TXB & TXS in the past but they caused issues for me.
My first requirement is to level shift SWD debug signals from 3.3V to a selectable voltage which ranges from 1.2V to 3.3V.
SWD has 2 signals
SWCLK is unidirectional and will be pulled low through 100K on the source, 3.3V side of the level shifter. The target side output of the level shifter has no pull up or down and feeds a high impedance processor input.
SWDIO is bi-directional and will be pulled high through a 100K on the 3.3V side of the level shifter. On the low voltage side of the level shifter the signal directly feeds the push-pull IO of the processor.
I was going to use the LSF but I don't now think it is the correct device to use.
My second requirement is a uni-directional single bit level shifter. The source is open drain and will be pulled up to a voltage between 1.0V and 3.3V. The high voltage side needs to behave like an open drain pulled to 3.3V through a resistor, although I can also work with a push pull on this side. My gut on this shifter is to use FETs but the Vth on all FETs I have looked at is too high.
Thoughts/suggestions?
Thanks,
Steve