If VIO drops below UVIO under voltage detection several functions is disabled. The transceiver switches off and disengages from the bus until VIO has recovered. When UVIO triggers, the tUV timer starts. If the timer times out and the UVIO is still there, the device enters sleep mode. See Figure 10-8, Figure 10-9. Once in sleep mode, a wake event is required to place the TCAN114x-Q1 into standby mode and enable the INH pin. As registers are cleared in sleep mode, the UVIO interrupt flag is lost. If the UVIO event is still in place, the cycle repeats. If during a thermal shut down event a UVIO event happens, the device automatically enters sleep mode. See Figure 10-24 on how UVIO behaves.
The device is designed to be an "ideal passive" or “no load” to the CAN bus if the device is unpowered. The bus terminals (CANH, CANL) have extremely low leakage currents when the device is unpowered, so they do not load the bus. This is critical if some nodes of the network are unpowered while the rest of the of network remains operational. Logic terminals also have extremely low leakage currents when the device is unpowered, so they do not load other circuits which may remain powered.
The UVLO circuit monitors both rising and falling edge of a power rail when ramping and declining.