Preliminary
CBC34813 EnerChip™ RTC
Important Reference Documents
For complete specifications of the integrated AM0813 Real-Time Clock, see here:
http://ambiqmicro.com
For complete specifications of the Cymbet 5µAh EnerChip and integrated power management circuit, reference
the CBC3105 datasheet here: http://www.cymbet.com/pdfs/DS-72-21.pdf .
The EnerChip and power management functions within the CBC34813 are configured as in Mode 1 (VMODE =
GND) as described in the CBC3105 DS-72-21 data sheet.
For guidelines regarding crystal selection and other important information pertaining to the AM0813, see here:
http://ambiqmicro.com/resource-center/
Functional Description of Integrated AM0813 Real-Time Clock
The AM0813 serves as a full function RTC for host processors such as microcontrollers. The AM0813 includes 3
distinct feature groups: 1) baseline timekeeping features with 32.768 kHz oscillator and 2) advanced
timekeeping features, and 3) basic power management features. Functions from each feature group may be
controlled via memory mapped registers. These registers are accessed using either an I2C serial interface (e.g.,
in the AM0803) or a SPI serial interface (e.g., in the AM0813). For more information on the AM0813, see here:
http://ambiqmicro.com/0800-series.
Low Power Operation
Minimum power operation will be achieved by turning off the charge pump in the power management circuit by
driving ENABLE low once the internal EnerChip has been charged - typically one hour to full charge at room
temperature.
The RTC has 3 low power modes, allowing the designer to make appropriate trade-offs between power
consumption and timing accuracy. Operating current drawn by the RTC is as follows:
<15 nA with RC oscillator
<20 nA with RC oscillator and autocalibration
<55 nA with crystal oscillator
In addition to the RTC current, the integrated power management circuit typically draws 20-25nA from the
EnerChip storage device at room temperature.
DS-72-38 V.01
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