The module enters a brownout condition whenever the input voltage dips below V_BROWNOUT (see Figure 8-4 and Figure 8-5). This condition must be considered during design of the power supply routing, especially if operating from a battery. High-current operations, such as a TX packet or any external activity (not necessarily related directly to networking) can cause a drop in the supply voltage, potentially triggering a brownout. The resistance includes the internal resistance of the battery, contact resistance of the battery holder (four contacts for a 2× AA battery), and the wiring and PCB routing resistance.

Figure 8-4 Brownout and Blackout Levels (1 of 2)

Figure 8-5 Brownout and Blackout Levels (2 of 2)

In the brownout condition, all sections of the device shut down within the module except for the Hibernate block (including the 32-kHz RTC clock), which remains on. The current in this state can reach approximately 400 µA. The blackout condition is equivalent to a hardware reset event in which all states within the module are lost. V_brownout = 2.1 V and V_blackout = 1.67 V

Table 8-1 lists the brownout and blackout voltage levels.