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3. Power Specifications.
Power supply
The nRF51 supports three different power supply alternatives:
• Internal LDO setup
• DC/DC converter setup
• Low voltage mode setup
See
Table
for the voltage range on the different alternatives.
circuitry”
for details on the schematic used for the different power supply alternatives.
Internal LDO setup
In internal LDO mode the DC/DC converter is bypassed (disabled) and the system power is
generated directly from the supply voltage VDD. This mode could be used as the only option or in
combination with the DC/DC converter setup. See DC/DC converter section for more details.
DC/DC converter setup
The nRF51 DC/DC buck converter transforms battery voltage to lower internal voltage with minimal
power loss. The converted voltage is then available for the linear regulator input. The DC/DC
converter can be disabled when the supply voltage drops to the lower limit of the voltage range so
the LDO can be used for low supply voltages. When enabled, the DC/DC converter operation is
automatically suspended between radio events when only the low current regulator is needed
internally.
This feature is particularly useful for applications using battery technologies with nominal cell
voltages
higher than the minimum supply voltage with DC/DC enabled. The reduction in supply voltage level
from a high voltage to a low voltage reduces the peak power drain from the battery. Used with a 3 V
coin-cell battery, the peak current drawn from the battery is reduced by approximately 25%.
Low voltage mode setup Devices can be used in low voltage mode where a steady 1.8 V supply is
available externally.
