Difference between SN74LVC16T245 and SN74LVCH16T245

Victor,

The 'H' indicates support for bus hold. Devices that do not support bus hold will not have the 'H'.

This app note goes into detail on the feature set of the SN74LVCXT245 and SN74LVCHXT245 set of devices. Section 6 (Floating Inputs with Bus Hold I/O) has more details about bus hold.

This FAQ is also very helpful.

Best Regards,
Nirav

Victor - My feedback is below:

Victor L-S said:

I will be driving the data lines via the GPIO headers on a EK-TM4C1294XL LaunchPad. The transceivers will be uni-directional only. Given that is there any preference between an H and non-H solution?

1. Are there external pulldown/pullup resistors on the data lines? If so, then I would recommend the non-H solution, since these resistors will keep the data lines at a valid voltage range.

2. If there are no external pullup/pulldown resistors on the data lines, then will the external driver guarantee that the data lines are at a valid voltage (i.e. the exeternal driver will always drive a valid high/low, and never tri-state its outputs)? If so, then I would recommned the non-H solution, since the external driver will prevent the data lines from floating.

If the answer to the above two questions is no, then I would recommend using the translator with bus hold (H version).

Victor L-S said:

The document SCES636B –AUGUST 2005–REVISED APRIL 2015 states...

Make sure to tie any unused input and output ports directly to ground.

Is this a better procedure than simply tying the unused inputs?

Yes, because it helps to reduce power dissipation.

Victor L-S said:

Is it correct to tie DIR to ground?

Can DIR be tied directly to VCCA? If not what is the recommended resister for a 3.3V VCCA?

You may tie DIR directly to GND or to VCCA since your signals are uni-directional, and thus there is no need to swtich the DIR state at any time.

Best Regards,
Nirav