LSF0101: LSF010x 1/2/8

user6376834

Part Number: LSF0101

Hi,

I want to use this component to interface my FPGA (1.8V) with external world.

The VCCA of the component would be 1.8V.

The VCCB would be 3.3V.

This configuration will work for sure.

But i want to keep the possibility to change the VCCB (using a switch on my board) to provide also 1.8V on the VCCB.

Why ? To protect my FPGA I/Os from bad usage ... The LSF0101/02 will be use as a barrier without real voltage translation. Is it possible ?

Thanks for your help.

0 Clemens Ladisch over 3 years ago

Guru 243770 points

This will not work; V_CCB must be at least 1 V higher than V_CCA.

If possible, use a direction-controlled translator. For bidirectional signals where pull-up resistors are allowed, use a TXS translator.

0 user6376834 over 3 years ago in reply to Clemens Ladisch

OK i understand.

Unfortunately the signal are potentially birectionnal. And with toggling Speed > 30MHZ. So TXS seems too slow.

So the solution is to use a controlled Voltage Translator instead ? Why not. I just need to add X pin from the FPGA.

Any reference to share with me ?

0 Clemens Ladisch over 3 years ago in reply to user6376834

Guru 243770 points

TXB translators are faster than TXS, but the strict load requirements make them unlikely to work with something called "external world".

Auto-bidirectional translators cannot buffer the signals, because they would not know with side should override the other one.

What exactly do you mean with "barrier"? A voltage translator is not necessarily more robust than a FPGA.

Logic forum