Level Shifter

[desowin]

How does the TI SN74CB3T3245 determine which way the data flows?
Have anyone used these? Does it work fine if some of the lines flow in the opposite direction than others?

All other level shifters I've seen, require the direction input, but the TI's one doesn't.

[deephaven]

How does the TI SN74CB3T3245 determine which way the data flows?
Have anyone used these? Does it work fine if some of the lines flow in the opposite direction than others?

All other level shifters I've seen, require the direction input, but the TI's one doesn't.

They are just FET switches which means they act a little bit like relay contacts where they join one i/o pin to another when enabled, and therefore pass data in either direction. They are called level shifters, because they are designed to be tolerant to input voltages uo to 5V but limit the output voltage to, say, 3.3V

[scrat]

So is the trick simply a diode clamping of both I/O to Vcc?
If I understand correctly, they are only down-shifting the level, which could have been done with a few resistors and diodes, but the IC provides 8 channels clamping and enable control in a single package.

[deephaven]

So is the trick simply a diode clamping of both I/O to Vcc?
If I understand correctly, they are only down-shifting the level, which could have been done with a few resistors and diodes, but the IC provides 8 channels clamping and enable control in a single package.

Performance will be better than using passive components, e.g. the on resistance is only 5 ohms. It also has an enable pin which could be useful - epecially if using more than one device for switching busses.

[desowin]

If it receives 2.4V on input, would it put 3.3V (assuming Vcc=3.3V) on output of that line?

[scrat]

From the internal schematic, it won't.

[desowin]

Oh, there's even a uncharacteristic for Vout in function of Vin in that datasheet