ADM3055E/57E Can Support Maximum CAN Nodes In The CAN Network by ISO 11898-2?

Hi Jack,

The maximum number of nodes on a CAN bus is going to depend on the loading characteristics and driving capabilities of each device connected to the bus, as well as the desired communication speed and physical implementation of the bus.

An upper limit to the maximum number of nodes on the bus can be estimated based on the ability of the driver to drive the effective bus load across the V_OD range specified in ISO 11898-2 (1.5V for normal bus load or 1.4V for extended bus load).  This load consists of the parallel combination of the bus termination resistors and the input resistance of all connected receivers .  Table 1 of the ADM3055E datasheet gives the receiver’s differential input resistance, 20-100 kΩ, and driver capabilities, V_OD = 1.4 V for R_L = 45 Ω.  Assuming that the only devices on the bus are ADM3055E and the buses are terminated with 120 Ω resistors, the worst-case maximum number of nodes can be calculated using 1/45 Ω = 2/120 Ω + N/20 kΩ, where N is the maximum number of nodes, giving a lower bound of a maximum 110 nodes on the bus.

In practice, this many nodes may be difficult to achieve at high data rates as parasitics at each stub are going to contribute to ringing on the signal that will compound with high numbers of stubs. Additionally, devices on the bus other than the ADM3055 will have different input resistances and driving capabilities which will change the limit for maximum nodes.

Nevertheless, if sufficient care is taken in designing the bus, it should be able to support significantly more than 30 nodes using the ADM3055E.

Rye

Hi Rye,
Thanks so much.

Jack