The TCAN1473A-Q1 implements a low-power wake receiver in the standby and sleep mode that uses the multiple filtered dominant wake-up pattern (WUP) defined in the ISO11898-2:2016 standard.

The wake-up pattern (WUP) consists of a filtered dominant bus, then a filtered recessive bus time followed by a second filtered dominant bus time. The first filtered dominant initiates the WUP and the bus monitor is now waiting on a filtered recessive; other bus traffic will not reset the bus monitor. Once a filtered recessive is received the bus monitor is now waiting on a filtered dominant, and again, other bus traffic will not reset the bus monitor. Immediately upon receiving of the second filtered dominant the bus monitor will recognize the WUP and drive the RXD terminal low, if a valid V_IO is present signaling to the controller the wake-up request. If a valid V_IO is not present when the wake-up pattern is received the transceiver drives the RXD output pin low once V_IO > UV_IOR.

The WUP consists of:

• A filtered dominant bus of at least t_WK(FILTER) followed by
• A filtered recessive bus time of at least t_WK(FILTER) followed by
• A second filtered dominant bus time of at least t_WK(FILTER)

For a dominant or recessive to be considered “filtered,” the bus must be in that state for more than t_WK(FILTER) time. Due to variability in the t_WK(FILTER) the following scenarios are applicable. Bus state times less than the t_WK(FILTER) minimum will never be detected as part of a WUP and thus no wake request will be generated. Bus state times between t_WK(FILTER) minimum and t_WK(FILTER) maximum may be detected as part of a WUP and a wake request may be generated. Bus state times more than t_WK(FILTER) maximum will always be detected as part of a WUP and thus a wake request will always be generated. See Figure 7-6 for the timing diagram of the WUP.

The pattern and t_WK(FILTER) time used for the WUP and wake request prevents noise and bus stuck dominant faults from causing false wake requests while allowing any CAN or CAN FD message to initiate a wake request.

ISO11898-2:2016 has two sets of times for a short and long wake-up filter times. The t_WK(FILTER) timing for the TCAN1473A-Q1 has been picked to be within the min and max values of both filter ranges. This timing has been chosen such that a single bit time at 500kbps, or two back to back bit times at 1Mbps triggers the filter in either bus state.

For an additional layer of robustness and to prevent false wake-ups, the transceiver implements the t_WK(TIMEOUT) timer. For a remote wake-up event to successfully occur, the entire wake-up pattern must be received within the timeout value. If the full wake-up pattern is not received before the t_WK(TIMEOUT) expires then the internal logic is reset and the transceiver remains in sleep mode without waking up. The full pattern must then be transmitted again within the t_WK(TIMEOUT) window. See Figure 7-6.

A recessive bus of at least t_WK(FILTER) must separate the next WUP pattern if the CAN bus is dominant when the t_WK(TIMEOUT) expires.

*The RXD pin is only driven once V_IO is present.

Figure 7-6 Wake-Up Pattern (WUP)