SLLA636 June 2024 TCAN3403-Q1 , TCAN3404-Q1
As seen from the functional block diagram of 5V CAN transceiver below, for the driver to be able to produce minimum differential voltage of 1.5V across CANH-CANL terminals, high side and low side transistors (highlighted in dotted red rectangle in Figure 2-1) have to be sized appropriately so that maximum drop across them is 3V when operating from 4.5V supply (since main 5V supply can vary by ±10%).
Correspondingly the specifications for CANH and CANL with respect to GND are specified in the physical layer standard as shown in Table 2-1.
Parameter | Conditions | Min (V) | Max (V) |
---|---|---|---|
VCANH | Dominant output, Bus load 50 Ω ≤ RL ≤ 65 Ω | 2.75 | 4.5 |
VCANL | 0.5 | 2.25 |
The CAN bus transceiver can be the only 5V component in the sub-system. With the modern MCU’s I/O supply going down to 3.3V, there is a possibility to eliminate the 5V rail altogether resulting in power stage simplification and cost saving by BOM reduction and PCB space reduction.
A high bus-fault tolerant CAN bus transceiver that is footprint compatible to standard 5V CAN transceivers, and that operates from a single 3.3V supply can help simplify the design and reduce cost by eliminating the need for a dedicated 5V supply.