Application Note
EnerChip™ CC as Backup Power for a Microchip MCP79410 RTC
Introduction
Cymbet EnerChips are solid state rechargeable batteries having distinguishing characteristics compared to
conventional rechargeable batteries. EnerChips have a high charge/discharge cycle life; low self-discharge;
simple voltage controlled charging; flat discharge voltage profile; have no flammable solvents to leak or catch
fire; are solder reflow tolerant; and are offered in low profile surface mount packages.
The EnerChip CC is a surface mount package containing a rechargeable solid state battery - the EnerChip -
with integrated battery management that includes charge control, discharge cutoff circuitry, and a battery
switchover (i.e., supply supervisory) function. EnerChip storage (discharge) capacity varies by product.
EnerChips are used in applications requiring backup, bridging, or transition power to maintain real-time clock
(RTC) operation or SRAM data retention in the event of main power interruption; wireless sensing as the main
power source when energy can be harvested from the ambient power and used to constantly trickle charge the
EnerChip; and as a power source to perform housekeeping for microcontrollers (MCUs) and peripherals when
main power is interrupted, to ensure an orderly shutdown or transition to low power modes.
Many applications demand ultra low power consumption from the various system components, particularly
when system power is derived from primary or rechargeable batteries. In systems utilizing RTCs, it is essential
that the standby power of the RTC be very low in order to achieve maximum run time from the backup power
source when main power is interrupted. A full-featured RTC now available from Microchip is the MCP79410. The
device has a VBAT auxiliary power pin to which a backup power source can be connected. This Application Note
describes use of the surface mount EnerChip CC as the backup power source for the MCP79410 RTC.
A typical application circuit is shown in Figure 1. Main power is fed to both the CBC3150 and MCP79410. When
the supply voltage drops below a specific threshold as detected by the CBC3150 and MCP79410, the EnerChip
solid state battery embedded in the EnerChip CC delivers power to the RTC through the CBC3150 VOUT pin.
AN-1046
Preliminary
Figure 1. Typical Application Circuit Using the EnerChip CC and MCP79410 Real-Time Clock.
Doc AN-72-1046 Rev A
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