The WAKE terminal is a bi-directional high-voltage reverse-battery protected input which can be used for local wake-up (LWU) requests via a voltage transition. A LWU event is triggered on either a low-to-high or high-to-low transition since it has bi-directional input thresholds. The WAKE pin could be used with a switch to V_SUP or to ground. If the terminal is unused it should be pulled to V_SUP or ground to avoid unwanted parasitic wake-up events.

Figure 9-9 WAKE Circuit Example

Figure 9-9 shows two possible configurations for the WAKE pin, a low-side and high-side switch configuration. The objective of the series resistor, R_SERIES, is to protect the WAKE input of the device 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:

With absolute maximum voltage, V_SUPMAX, of 45 V and maximum allowable I_IO(WAKE) of 3 mA, the minimum required R_SERIES value is 15 kΩ.

The R_BIAS resistor is used to set the static voltage level of the WAKE input when the switch is released. 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 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:

With V_SUPMAX of 45 V, V_IH of 44 V at I_IH of 3 µA, the R_BIAS resistor value must be less than 330 kΩ. It is recommended to use R_Series less than 50 kΩ to provide better margin for the WAKE pin voltage to rise above V_IH when the switch is released.

The LWU circuitry is active in sleep mode.

The WAKE circuitry is switched off in normal mode.