The internal LDO provides a regulated voltage to the internal digital core and analog circuitry. The internal LDO has a nominal output voltage of 2.5 V and can support up to 10 mA of external load. During EEPROM programming, the output voltage is elevated to 3.6 V as described in Section 8.5.1. Therefore, any external circuitry connected to INT_LDO must be capable of supporting that voltage.

When system power fails, the UVLO comparator triggers the power-down sequence. If system power drops below 2.3 V, the digital core is reset and all remaining power rails are shut down instantaneously and are pulled low to ground by their internal discharge circuitry (DCDC1-4 and LDO1).

The internal LDO reverse blocks to prevent the discharging of the output capacitor (C_{INT_LDO}) on the INT_LDO pin. The remaining charge on the INT_LDO output capacitor provides a supply for the power rail discharge circuitry to ensure the outputs are discharged to ground even if the system supply has failed. The amount of hold-up time specified in Section 7.5 is a function of the output capacitor value (C_{INT_LDO}) and the amount of external load on the INT_LDO pin, if any. The design allows for enough hold-up time to sufficiently discharge DCDC1-4, and LDO1 to ensure proper processor power-down sequencing.

Figure 8-10 Internal LDO and UVLO Sensing