STAND_BY_POWER_FOR_NON_VOLATILE_CMOS_RAMs

Published:2009/7/2 4:46:00 Author:May | From:SeekIC

Circuit Notes To prevent loss of data when a CMOS RAM is switched from normal operation (VCC=5 volts) to stand-by mode (VCC=VgAT) it must be ensured that the CS pin goes near the VCC rail at all times. Ac coupling to the chip select is made through capacitor C, breaking the dc current path between Vgg (and hence VgAT) and the decoder output. So, whatever the impedance state of the decoder in power down, the battery will provide current only for the RAM, low enough to keep the voltage at CS near to VCC.



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