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 VDD levels are above a sufficient threshold, the charge pump does not improve analog performance, but also consumes additional current. Allowing hardware to monitor VDD and determine when to enable the charge pump prevents unnecessary current consumption.
When the CPON bits are configured as ‘10’, charge pump
hardware monitors VDD and compares the VDD levels to a reference
voltage threshold (VAUTO), which is set to 4.6V. When hardware detects a
VDD level lower than the threshold, the charge pump is automatically
enabled. If VDD 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 VDD. In this case, charge pump hardware monitors all analog
peripherals, and once an analog peripheral is enabled, hardware begins to compare
VDD to VAUTO. When hardware detects a VDD level
lower than the threshold, hardware enables the charge pump. If VDD returns to
a level above the threshold, or if the analog peripheral is disabled, the charge pump is
automatically disabled.