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Fast LL 2:1 Mux (tpd < 0.5ns)

YILMAZ KIRÇİÇEK

Intellectual 905 points

Other Parts Discussed in Thread: SN74CBTLV1G125

Hi all,

We need to mux incoming two fast signal with tiny components. ___2G157 part seems to be ok but they have max. 4ns propagation delay.

So I wonder if can two SN74CBTLV1G125 be used as figure below. This device has max. 0.25ns tpd.

According to datasheet SN74CBTLV1G125 has isolated during power up. So there will not be a problem on power up but what about CTRL switching?

CTRL signal can only toggle once on boot time. But Ten / Tdis delays are 4ns. This means output of the two SN74CBTLV1G125 can be shorted approx.4ns.

I can not insert any resistor on X1 / X2 paths or extra logic or delay for OE inputs. Will I have any problem with this configuration ? Is there any other fast LL 2:1 mux solution that you can advice?

Best regards.

over 13 years ago

0 Chris Cockrill over 13 years ago

TI__Mastermind 46480 points

A pullup resistor on the OE pins woud stop the bus contention during powerup.

0 YILMAZ KIRÇİÇEK over 13 years ago in reply to Chris Cockrill

Intellectual 905 points

Hi Chiris,

Thank you for your response.

But problem is not about power up. Your advice is clear and stated on datasheet.

Problem occurs when I toggle the CTRL signal. Because devices has 4ns Ten / Tdis delays. (Ignoring inverter tpd)

Both device can be active for a few ns. I wonder that will I encounter a problem.

(Please do not advice small series resistor.)

Best regards.

0 Chris Cockrill over 13 years ago in reply to YILMAZ KIRÇİÇEK

TI__Mastermind 46480 points

You could use this part to replace all 3 of the parts shown. SN74LVC1G3157

if you need to use the circuit above you could put a LVC1g34 on the othe OE to balance out the enable disable times

0 YILMAZ KIRÇİÇEK over 13 years ago in reply to Chris Cockrill

Intellectual 905 points

Hi Chris,

I thank you very much for your time and support.

SN74LVC1G3157 is the best solution.

I could not see it because it is listed on Analog Switch/Multiplexer (less than or equal to 5V) group, but I was looking on logic mux. section.

Best regards.