TXS0104E: What problem cause TXS0104E's output signal do not follow inut signal?

Eggsy Pang

Part Number: TXS0104E
Other Parts Discussed in Thread: SN74AHC125, TXB0104, SN74LV4T125

Hi team,

My customer used TXS0104E and below is SCH. And LE_OUT signal go from High to Low level, SPLINDLE_OUTBUF will follow to go from High to Low level. And FPGA_MS also will follow to go from High to Low level.

But when LE_OUT signal go from Low to high level, SPLINDLE_OUTBUF would not follow it to go from Low to high level. FPGA_MS is too.

Below is the waveform of LE_OUT, SPLINDLE_OUTBUF, and FPGA_MS.

But we remove the TXS0104E chip from the board. LE_OUT signal go from Low to high level and SPLINDLE_OUTBUF would follow it to go from Low to high level.

Do you know why?

Thanks!

over 4 years ago

0 Clemens Ladisch over 4 years ago

Guru 287860 points

Please zoom in on the rising edge of LE_OUT. I suspect that the SPLINDLE_OUTPUF line has ringing that causes the TXS's edge accelerators to falsely trigger and oscillate.

Are there long traces, or anything else with a high capacitance?

For unidirectional downtranslating, a 3.3 V buffer with overvoltage-tolerant inputs (e.g., SN74AHC125) would be simpler and more robust.

0 Eggsy Pang over 4 years ago in reply to Clemens Ladisch

TI__Expert 4985 points

Hi Clemens,

The traces of SPLINDLE_OUTBUF from PS2802 to TXS0104E is 110mm.

There is not Cap between SPLINDLE_OUTBUF trace.

Zoom in on the rising edge of LE_OUT in below pic.

0 Clemens Ladisch over 4 years ago in reply to Eggsy Pang

Guru 287860 points

The sample rate is too low to see much. Please re-capture at that zoom level. (I want to see if anything is happening on SPLINDLE_OUTBUF at that time.)

110 mm might be too long for the TXS. There already is something that looks like a spike.

0 Eggsy Pang over 4 years ago in reply to Clemens Ladisch

TI__Expert 4985 points

Hi Clemens,

Do we have aother part pin2pin to replace it in this application?

Customer will re-capture it again.

0 Clemens Ladisch over 4 years ago in reply to Eggsy Pang

Guru 287860 points

The only P2P device is the TXB0104, which would have the same problem.

0 ShreyasRao over 4 years ago in reply to Clemens Ladisch

TI__Guru 59160 points

try removing the1uf cap on the Le_out line and see if there is a pulse on splindle_buf.

As Clemens suggested, AHC125 or sn74LV4t125 maybe suitable for 5v to 3.3V level translation.

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TXS0104E: What problem cause TXS0104E's output signal do not follow inut signal?