TCAN4551-Q1: Power consumption and power supply of tcan4551-q1

Hi Sheng,

This is a good question. To start, I'll mention that the dominant with bus fault condition should not last more than a few 10s of µs in most systems (data rate dependant). When a bus fault occurs that causes the transceiver to reach its current limit, the data on the CAN bus will be compromised in the majority of cases. When the TCAN4551 controller recognizes that it is unable to transmit data on the bus, it will enter an error-passive state and cease attempts to drive the bus dominant. This means that the fault current will only be needed for the few µs between recognition of this condition and reaction to error-passive mode. The LDO in this device is capable of providing sufficient power for such a short period. The device also has a thermal shutdown mechanism which will automatically switch off the power before the IC gets too hot. 

During normal operation, the maximum current needed by the transceiver will be 90mA during a dominant state depending on the bus load. While driving data, the transceiver will be switching between dominant and recessive states depending on the data being transmitted, so the average power needed will be somewhere between the recessive (15mA) and dominant (90mA) requirements (averaged by %dom). 

For power supply considerations, it is optimal to ensure the transceiver is alloted at least the average power required around 75mA (~70% dom with max load). Ensure that sufficient bulk capacitance is available on this supply to accommodate for short spikes up to 180mA (voltage drop is acceptable as long as the recommended range is maintained). 

Let me know if you have any more questions.

Regards,
Eric Schott