Battery Back Up Power Supply
Original Publication Date: 1980-Aug-01
Included in the Prior Art Database: 2005-Feb-13
A simple battery back-up power supply for a memory is shown in Fig. 1. When the system is switched on, the memory 1 is supplied with current from the supply terminal 2 through diode 3. A decoupling capacitor 4 is provided. In the event of supply power failure, the memory is powered by a battery 5 normally isolated by diode 6. The voltage drop across diode 3 means that the system supply voltage applied to terminal 2 must be greater than voltage required to operate the memory 1. Since in many systems only one voltage is available (5 volts +/-10 percent) and this is the memory operating voltage, this voltage drop presents a problem.