TXS0108E: Level Shifter

Dear Clemens,

GroupB are the high voltage level 3.3V input to level shifter, GroupA are the expected 1.8V output.

Are there any pull-up/-down resistors, capacitors, or other components connected to any of the lines?

What is the output? Please show an oscilloscope trace.

Case1: OE pin made pulled down by 10KE resistor. The expected output is 1.8V PCM Signals. But we didn't get this.

Case2: OE pin made pulled high by 10KE resistor. The expected output is 1.8V PCM Signals. But we didn't get this.

Case3: OE pin is made pulled down until VCCA and VCCB are powered up and then made OE pin as pull high once VCCA and VCCB are powered. then also expected output 1.8V PCM signals are not coming.

Note: Input to the level shifter is 3.3V PCM signals from FPGA the expected output from the level shifter is 1.8V PCM  signals.

PCLK frequency is 2.048MHz

Please check the schematics part and suggest if any modifications are required.

Thanks & Regards,

Sai Ravali

What exactly do you mean with "didn't get this"? What is the output voltage?

Dear Sir,

You can see in the image D18 is the input we are giving to level shifter from FPGA. 

We are tracing the output at  D4 which is the output from the level shifter which is expected to be 1.8V PCLK signal. But we are not getting any signal.

We are checking with INTRONIX Logic Analyser in this we cant check voltage level. But atleast we have to get a signal at PCLK which is not appearing.

Note: operating PCLK frequency is 2.048MHz.

I do not know how your logic analyzer is configured. But the line always being low is not a likely error. An oscilloscope trace would be more helpful.

Please check the TXS's power supply. Try replacing the chip.

We are getting 1.8V and 3.3V at the respective pins. Yes, we have replaced the IC. Sir, my doubt is can we use TXS0108ERGYR or TXB0106 (which is 6 channel) for frequency of 2.048MHz? I have seen the datasheet is showing an application circuit output waveforms for 2.5MHz. Still please confirm that can we use TXS0108ERGYR or TXB0106 for operating frequency of 2.048MHz?

Yes, they can support 2 MHz.

But you have not given me all the information I've asked for. Please provide the trace length, or show a photograph of the board.

Hi Sai,

Is the issue only visible on one of the channels or multiple? Are we able to get clarification on Clemens' suggestions of the external loading conditions at the I/Os not shown in the above schematic? 

Regards,

Jack 

Please check the attached Screenshots for trace length.