SN74LVC2T45: Maximum Capacitive Load and maximum cable distance

Selim Ozdogan

Part Number: SN74LVC2T45
Other Parts Discussed in Thread: SN74LXC2T45

Hello,

I am designing a FMC board for the communication between two main boards. The FMC board will be connected to both master and slave boards and two FMC will be connected through Cat5 ethernet cable. Master is foreseen to control 3 slaves. All slaves are controlled through common SPI pins and they differ on Chip Select. I am forced to use SN74LVC2T45 for configurable voltage level translation between Master and Slave Boards. The distance between two boards will be around 10 meters. Can you please provide information about the capacitive load capacity of SN74LVC2T45 so that I can try to figure out maximum distance I can transmit my signals through Cat5 ethernet cables. I am aware that 10 meters is far away. Depending on the maximum distance achieved with SN74LVC2T45, I am planning to design an intermediate repeater board between two FMC.

Regards,

Selim

over 2 years ago

0 Michael Ikwuyum over 2 years ago

TI__Guru 50726 points

Hi Selim,

Please help see [FAQ] What is the maximum capacitive load that a logic device can drive? further clarifying, thanks.

Best Regards,

Michael.

0 Selim Ozdogan over 2 years ago in reply to Michael Ikwuyum

Prodigy 80 points

Hi Michael,

Thanks for the link. I checked it.

In our case we want to send SPI signals with a SPI clock frequency at maximum 10MHz. (We will be probably using it at very low frequencies, less than 1MHz).

I would like to ask if the following configuration would be working if we use several short cables connected to master board - repeater board(s)(depending on achievable cable length based on the capacitive load) - slave board as given in the following figure?

Regards

0 Clemens Ladisch over 2 years ago in reply to Selim Ozdogan

Guru 316760 points

Intermediate buffers add a propagation delay, and LVC outputs should be strong enough to drive 4 m of cable. So this is probably not an improvement. (And use the more modern SN74LXC2T45.)

Logic

Logic forum

SN74LVC2T45: Maximum Capacitive Load and maximum cable distance