Other Parts Discussed in Thread: SN74GTL2014, LSF0108
Hi,
What would happen if one of channel A of SN74AXC8T245 is open while others are configured its direction ?
Any leakage would happen and any prevention action to be taken ?
Thanks
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Hi,
What would happen if one of channel A of SN74AXC8T245 is open while others are configured its direction ?
Any leakage would happen and any prevention action to be taken ?
Thanks
Hi Clemens,
In https://e2e.ti.com/support/logic-group/logic/f/logic-forum/788628/faq-what-should-be-done-with-unused-i-o-pins-of-the-level-translator-devices , it mentioned that AXC has weak pull down internally. So it can be left open for unused input.
Bu in section 6.3 footnote 3 as you mentioned, it said all unused input must be held either at GND or VCC.
Could help to explain more which is the correct one ?
Thanks.
As far as I know, the datasheet is correct. (The LXC and AXC families are different.)
Hi Woon,
The AXC datasheets are planned to be updated as they can be left floating, thanks.
Best Regards,
Michael.
Hi Woon,
Only GTL2014 needs to have a logic level input.
LXC can be left floating as well. Similar to the datasheet as shown below. AXC is planned to be updated similar to LXC, thanks.
Best Regards,
Michael.
hi Michael,
We have 1kohm weak PU at microcontroller. Is it enough for SN74GTL2014 pull up at GTL side for frequency of 125MHz ?
Hi Woon,
It will also depend on your load similar to the below. Please see the short video on Up Translation with LSF to help further clarify.
I would further suggest trying stronger pull-ups similar to figures 5 and 6 of the datasheet and adjust accordingly for your acceptable signal integrity, thanks.
Best Regards,
Michael.
Hi Michael,
SN74GTL2014 is family of LSF or LXC ?
We used both SN74GTL2014 and SN74AXC8T245 for bidirectional translation.
For SN74GTL2014 , either from 0.91V to 3.3V or from 3.3V to 0.91V.
For SN74AXC8T245, it is translated from 3.3V to 1.2V or from 1.2V to 3.3V.
Device at GTL2014 B side is open drain input receiver with weak PU/PD; it is also output drive with push/pull.
Device at AXC B side is IO buffer model or CMOS buffer model.
Could you help to comment if we can have PU at GTL2014 A side instead ?
It is because we have only weak PU at receiver of GTL2014 B side.
Hi Woon,
The GTL device is similar to the LSF family.
Yes, you can have pull ups on both sides similar to the below, thanks.
Best Regards,
Michael.
The GTL2003 would be similar to the LSF0108, but the GTL2014 is not:
As far as I can see, this question was already answered here: Open on one of channel B of SN74GTL2014
Hi Woon,
Apologies; I also confused the GTL2014 with the GTL2003.
Yes you can have any voltages within the recommendations below from the datasheet, thanks.
Best Regards,
Michael.
OK. thanks.
I would have pull up at B-side of GTL2014 in bi-directional control of this B-side.
Hi Woon,
Could you help clarify what the concern is? Do you have a block diagram or schematic of what you mean? Thanks.
Best Regards,
Michael.
Hi Michael,
We have bidirectional IO ( either input or output to B side), so it would have PU at B side of GTL2014. Does it the correct implementation ?