Hi,
I am wondering if the SN74CBTLV3245A 3.3V 8-Channel 1:1 Bus Switch can be used with LVDS ?
Thanks,
Elliot
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Hi,
I am wondering if the SN74CBTLV3245A 3.3V 8-Channel 1:1 Bus Switch can be used with LVDS ?
Thanks,
Elliot
Thanks Adam, Just wanted to make sure there wouldn't be any issues with the timing and impedance.
Elliot
Hi Adam, It seems the Impedance changes with the voltage for example with a VCC of 3.3V and an input voltage of 2.4V, and a current of 15mA I see a typical Ron of 10ohms. What would it be for a voltage of 1.3V to 1.9V and current of 3.5mA? and can two pins (A1 and A2 for example) have a differential impedance specification (LVDS requires 100 ohm differential impedance)?
Elliot,
The SN74CBTLV3245A is a FET switch which is non-linear such as a mechanical switch. The on-state resistance of the FET changes as the input on the source of the FET changes which varies the FETs Vgs (gate to source voltage)
The graph below is the Ron as the input voltage sweeps for an SN74CBTLVXXXX family of switches. The 1.3 V and 1.9V look to be about 3-4 ohm Ron.
There is more information on switch performance in this application note
I believe most LVDS receivers have the 100 ohm differential impedance integrated into the IC and you will just have the 4ohm losses on the transmission line due to the switch Ron.
Thank you,
Adam
Thanks Adam,
Yes LVDS requires 100 ohms at the termination end, and that may or may not be included on the chip, but it also requires 100 ohm differential transmission line impedance.
and when adding the chip we get a discontinuity in that transmission line differential impedance.
That is the concern I have.
Thanks again,
Elliot