AN-1008 Application Note Using Cymbet™ EnerChip™ Batteries Instead of Coin Cells and Super Capacitors Introduction Benefits of Using Cymbet Enerchips™ Primary and secondary (i.e., rechargeable) coin cell batteries, Instead of Coin Cells and Super as well as super capacitors, have been in use for years as Capacitors auxiliary power sources for applications including SRAM, real-time clocks, and microcontrollers. Now, a new type of rechargeable battery is available from Cymbet Corporation, the leader in thin film rechargeable micro-batteries. Cymbet™ EnerChip™ thin film, solid state batteries feature all solid state construction, are packaged in standard integrated circuit packages, and can be reflow soldered for high volume PCB assembly. They are ideal as rechargeable backup power sources for clocks, memories, microcontrollers and other lowpower circuits where data or timing information must be retained in the absence of primary power. These new energy storage devices present significant advantages over conventional coin-type batteries and super capacitors in applications requiring backup power. Features: • • • • • • Solid state reliability Low profile surface mount packaging Simple charge control Very high charge/discharge cycle life High temperature solder reflow tolerant Component class Benefits: • • • • Reduced size Fewer parts Lower overall cost Higher reliability Applications: • • • • • • • • • Utility meters Digital video recorders Set-top decoders PABX hubs RAID controllers Point-of-sale terminals Clock radios Microwave ovens Cellular phones The high charge/discharge cycle capability makes these rechargeable batteries ideal as backup power sources for low power circuits in cellular phones, pagers, point-of-sale terminals, office equipment, home appliances, and other devices where protecting data or timing information is either essential to the enterprise, or simply gives convenience to the consumer. Another key advantage to using EnerChips is realized in total energy savings, particularly in battery operated equipment. For example, consider the case where a super capacitor is used to provide backup power for a device operated by a primary coin cell. This could be a home thermostat, a remote sensor, a portable RFID reader, portable medical instruments, or any other device operating from a user-replaceable battery. The coin cell or prismatic battery is used to power the system under normal operating conditions, while the super capacitor provides a short-term supply of energy to maintain memory or real-time clock operation while the main battery is being replaced or recharged. Because of the high self-discharge of many types of super capacitors, and because the capacitor must always be fully or nearly charged so that it will have a ready supply of charge when needed unexpectedly, the main battery must be continuously or regularly charging the capacitor. As shown in Table 1, this results in a significant current drain on the battery, diminishing its service life. A Cymbet EnerChip is a preferred solution, as the selfdischarge of these batteries is substantially lower than that of the super capacitor. This results in negligible wasted energy and thus increases the useful life or time between recharge cycles of the main battery. Moreover, the EnerChip provides the backup energy equivalent to or greater than the super capacitor while occupying less volume – an advantage in space-constrained devices. © Cymbet Corporation • 18326 Joplin Street, Elk River, MN 55330 • 763-633-1780 • www.cymbet.com DOC-111008 RevA Page 1 AN-1008: Using Cymbet EnerChip™ Batteries Instead of Coin Cells and Super Capacitors Table 1. Amount of Wasted Energy in Maintaining Charge on Super Capacitors. Device Equivalent Charge (µAh) Self-Discharge (%/day) 12 50 20 80 0.1 0.1 30 30 CBC012 CBC050 0.047 F 0.2 F Supplemental Charge Required (µAh) per 10 years CR2032 Capacity (mAh) % of CR2032 Used in Compensating for SelfDischarge 43.2 180 21600 86400 225 225 225 225 0.0192 0.08 9.6 38.4 A summary of the key advantages of using EnerChips instead of primary coin cells, rechargeable coin cells, and capacitors, is given in Table 2. It is clear that the Cymbet EnerChip offers the ease of implementation, low cost assembly, performance advantages and service life necessary to support the backup power requirements of today’s electronic systems. Table 2. Features and Benefits of Cymbet EnerChip Thin-Film Batteries Feature Capacitor Primary Coin Cell Rechargeable Coin Cell Cymbet Cymbet Advantage Solder reflow tolerance Select products No Select products Yes Low cost assembly Fast recharge No N/A No Yes Always ready for use High cycle life Yes N/A No Yes Component class Charge circuit Simple N/A Simple Simple Low cost, small footprint control circuit Self-discharge High Low Low Low Longer back-up time © Cymbet Corporation • 18326 Joplin Street, Elk River, MN 55330 • 763-633-1780 • www.cymbet.com DOC-111008 Rev01 Page 2