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Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2002-Jan-03

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James E. Berry Frank Fernandez


Many products today arc implementing volatile memory systems with rechargeable battery backup for those periods of time when the main system power sup- ply is turned off. This is especially true in systems where main cell battery life is a critical concern, such as in a digital pager. Since the products on time may be rela- tively short (i.e., the length of one business day or less), it is required for the backup source to be charged to its full potential as soon as possible. Under certain condi- tions, such as the case when the backup ceil is deeply discharged, conditions may arise that stress the current sourcing capability of the memory's main power source. For instance if the backup cell is recharging from a deep discharge, the system may be required to speed up the microprocessor and at the same time turn on high cur- rent peripheral devices such as a display, memory, etc. The added current required to quickly recharge the backup cell may push the system load beyond the limi- tations of the power source. This can easily occur in systems with a low power DC/DC converter, such as in a digital pager.