AN-1027 Datasheet, PDF (1/3 Pages) Cymbet Corporation – Ultra Low Power Microcontroller Backup Using the EnerChip

Preliminary
AN-1027
Application Note
Ultra Low Power Microcontroller Backup Using the EnerChip™ CC
Introduction
Cymbet EnerChips are solid state rechargable batteries having distinguishing characteristics compared to
conventional rechargeable batteries. EnerChips have a high charge/discharge cylce 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. EnerChips are used in applications requiring backup, bridging,
or transition power to maintain real-time clock 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.
In MCU-based applications demanding ultra low power consumption, it is essential to reduce or eliminate the
power drawn by components peripheral to the MCU. This Application Note describes a method to completely
eliminate the power drawn by the EnerChip CC integrated battery management circuitry when the system is in
the normal operating mode. This approach enables a backup battery solution that does not draw power when
in normal run mode, thus maximizing the main battery life in battery powered systems.
VDD
Q1A
1
6
CBC3112 or CBC3150
4 _VCHG
CP ⁹
1 _VBAT
6 _VMODE
CN ¹⁰
5 _EN
RESET ⁸
3 _VDD
VOUT ²
C5
0.1uF
5
Q1B
C4
10uF
C6
10uF
GPIO
GPIO
GPIO
GPIO
GPIO
GPIO
GPIO
GPIO
MCU with Supply Supervisor
VDD
GND
Figure 1. Typical Application Circuit Using the EnerChip CC and Microcontroller for Ultra Low Power Operation.
©2008 Cymbet Corporation • Tel: [phone] • www.cymbet.com
Doc AN-72-1027 Rev01
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