28.2 Automatically Enabled

The charge pump can also be enabled automatically. This allows the application to determine when to enable the charge pump. If the charge pump is enabled while V_DD levels are above a sufficient threshold, the charge pump does not improve analog performance, but also consumes additional current. Allowing hardware to monitor V_DD and determine when to enable the charge pump prevents unnecessary current consumption.

When the CPON bits are configured as ‘10’, charge pump hardware monitors V_DD and compares the V_DD levels to a reference voltage threshold (V_AUTO), which is set to 4.6V. When hardware detects a V_DD level lower than the threshold, the charge pump is automatically enabled. If V_DD returns to a level above the threshold, hardware automatically disables the charge pump.

When the CPON bits are configured as ‘01’, charge pump hardware waits for an analog peripheral, such as the ADC, to be enabled before monitoring V_DD. In this case, charge pump hardware monitors all analog peripherals, and once an analog peripheral is enabled, hardware begins to compare V_DD to V_AUTO. When hardware detects a V_DD level lower than the threshold, hardware enables the charge pump. If V_DD returns to a level above the threshold, or if the analog peripheral is disabled, the charge pump is automatically disabled.