TLIN1029-Q1: Max length

Michiaki-san,

You're correct about the specification.

This definition allows for the designer to design without too much worry regarding the capacitance and inductance of the cable. Take a look at these figures that show the effect of increasing capacitance on a LIN bus (orange line) and how the rising edge is too slow, resulting in errors on RXD (blue line). These figures are from TI's LIN Protocol and Physical Layer Requirements application note.

If you use a bus length above 40 m, you will be exceeding the maximum allowed by the LIN specification.

For longer distances, is another communication protocol (such as CAN) possible? CAN allows for longer bus lengths depending on bit rate (for example, 250 meters at 250 kbps).

Best,

Danny

Michiaki-san,

Well, I was just trying to get an idea for what was being considered. If we are talking about hundreds and hundreds of meters, then I would expect to see degradation of signal significant enough to cause errors. But if it is only a few meters, then the customer would be out of LIN spec (which you mentioned is okay for the customer) but likely still functional.

One option is the possibility of reducing the data rate if the rise/fall times become too long.

Ultimately, my answer is that the transceiver does not have any implicit characteristics that make it impossible to operate across 41 meters or longer. The 40 meter specification comes from the LIN standard. As shown by Figure 12, Figure 13, and Figure 14 of my earlier post, it would most heavily be impacted by effective bus capacitance. Generally, 10 nF serves as the upper limit for capacitance along the bus.

Best,

Danny