The WAKE terminal is a high voltage input terminal which can be used for local wake up (LWU) requests via a voltage transition. The terminal triggers a local wake up (LWU) event on either a low-to-high, or a high-to-low transition since it has a bi-directional input threshold (falling or rising edge).

This terminal may be used with a switch to V_SUP or to ground. If the terminal is unused it should be pulled to ground or V_SUP to avoid unwanted parasitic wake up events.

Figure 8-6 TCAN1043xx-Q1 WAKE Circuit Example

Figure 8-6 shows two possible configurations for the WAKE terminal, the low-side and high side switch configurations. The objective of the series resistor, R_SERIES, is to protect the WAKE pin of the transceiver from over current conditions that may occur in the event of a ground shift or ground loss. The minimum value of R_SERIES can be calculated using the maximum supply voltage, V_SUPMAX and the maximum allowable current of the WAKE pin, I_IO(WAKE). R_SERIES is calculated using:

If the battery voltage never exceeds 58V DC, then the R_SERIES value is approximately 20kΩ.

The R_BIAS resistor is used to set the static voltage level of the WAKE pin when the switch is not in use. When the switch is in use in a high-side switch configuration, the R_BIAS resistor in combination with the R_SERIES resistor sets the WAKE pin voltage appropriately above the V_IH threshold. The maximum value of R_BIAS can be calculated using the maximum supply voltage, V_SUPMAX, the maximum WAKE threshold voltage V_IH, the maximum WAKE input current I_IH and the series resistor value R_SERIES. R_BIAS is calculated using:

If the battery voltage never exceed 58V DC, then the R_BIAS resistor value must be less than 60kΩ.

For lower current consumption, the low-side switch configuration is the ideal architecture.

The LWU circuitry is active in Section 8.4.6, Section 8.4.4 and Section 8.4.5. If a valid LWU event occurs the device transitions to standby mode. The LWU circuitry is not active in Normal mode or Silent mode.

To minimize system level current consumption, the internal bias voltages of the terminal follows the state on the terminal with a delay of t_WAKE(min). A constant high level on WAKE has an internal pull-up to V_SUP and a constant low level on WAKE has an internal pull-down to GND. This minimizes the current flowing into the WAKE pin under these steady-state conditions, and so does not need to be factored into calculations of the total draw from V_SUP.

The RXD pin is only driven once V_IO is present.

Figure 8-7 Local Wake Up – Rising Edge

The RXD pin is only driven once V_IO is present.

Figure 8-8 Local Wake Up – Falling Edge