JAJSH69 データシート

JAJSH69D January 2018 – June 2022 TCAN4550-Q1

PRODUCTION DATA

8.4.6.7.2 UV_IO

If V_IO drops below UV_IO under the voltage detection threshold, several functions are disabled. The transceiver switches off until V_IO has recovered. The input clock or crystal circuits are disabled and the IO between the TCAN4550-Q1 and microprocessor is not active. When UV_IO triggers, the t_UV timer starts. If the timer times out and the UV_IO is still there, the device enters sleep mode, see Figure 8-5. Once in sleep mode, a wake event is required to place the TCAN4550-Q1 into standby mode and enables the INH pin. As registers are cleared in sleep mode the UV_IO interrupt flag is lost. If the UV_IO event is still in place, the cycle repeats. If during a thermal shut down event a UV_IO event happens, the device automatically enters sleep mode.

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 it does 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.

Table 8-6 Under Voltage Lockout I and O Level Shifting Devices

V_SUP	V_IO	V_CCOUT	DEVICE STATE	BUS	RXD_INT
> UV_SUP	> UV_VIO	> UV_CCOUT	Normal	Per TXD_INT	Mirrors Bus
> UV_SUP	> UV_VIO	< UV_CCOUT	Protected	High Impedance	High (Recessive)
< UV_SUP	> UV_VIO	NA	Protected	High Impedance	High (Recessive)
> UV_SUP	< UV_VIO	> UV_CCOUT	Protected	Recessive	High Impedance
< UV_SUP	< UV_VIO	NA	Protected	High Impedance	High Impedance

Note:

Once an under-voltage condition and interrupt flags are cleared and the V_SUP supply has returned to valid level, the device typically needs t_{MODE_CHANGE} to transition to normal operation. The host processor should not attempt to send or receive messages until this transition time has expired. If EN is low and V_SUP has an under-voltage event, the device goes into a protected mode which disables the wake-up receiver and places the RXD_INT output into a high impedance state.

8.4.6.7.2 UVIO

8.4.6.7.2 UV_IO