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Should we use a 1.8V LDO to power the Apollo 3 Blue on a CR2032 coin cell?



  • Andre Belanger

    Hello Etienne,

    For best battery life you should definitely NOT use an LDO between the coin cell and the Apollo3Blue.

    Apollo3Blue includes internal DC-DC regulators to generate the very low core voltages, and these internal DC-DC will be much more efficient that an external LDO.  The mW consumed by Apollo3Blue will be pretty consistent across the full voltage range 1.8V to 3.3V (slightly lower at 1.8V), but the mA will be higher much at 1.8V versus 3.3V.

    What that means is that Apollo3Blue current consumption at the battery will be roughly the same for these two options:

    Battery connected direct to Apollo3Blue

    Battery connected through efficient DC-DC Buck regulator which generates 1.8V for Apollo3Blue.


    However, if you use an LDO to drop the battery to 1.8V, the Apollo3Blue current consumption at the battery will be about 60% higher.


    In most systems, you will likely see lower overall system power if you use an efficient DC-DC Buck to generate a 1,8V system power.  However, this power savings will mostly be from the other components in your system, as well as lower power for any high speed interfaces (SPI, I2C, etc) since less energy will be spent toggling the pins.  If you have components in your system that require 3V then it may be easier to just run direct from the battery.


    Best regards,


  • Étienne Castanié

    Dear Andre,


    Thank you very much for your quick and detailed answer.


    Following your advice, we will try to evaluate whether the other peripherals and the communication buses impact the power consumption in the case where no dcdc is used. If the current consumption impact is reduced, we will connect directly the whole board to V_bat.


    Best regards,



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