MEMORY DATABOOK - Al Kossow's Bitsavers

-----------------------. APPLICATIONS.Figs. 4 and 5 are examples of circuits capable of generatinga POWER FAIL output signal. In these circuits, theC2 capacitance must be rather large, the importantpoint being the need for a smooth gradual change inCMOS Vee when the system power is cut. See next pagefor further details.TTL VeeSystem j 0,CMOS Veebattery 0, : 2N2907 or 2SA495c,l+ V... Rc --l +lc,0, : 2N2222 or 2SC372R, R. --; R. : lK R2 : 100l-POWER D, /0,1 Rs : 500 R4 : 47K... ~FAIL D, : 3.6V Rc : 200R.Ni-Cad : 3.6V0,Rs,l(70mAH)"*'Fig. 4.-------..... POWER FAIL signal.-----~----_r-_+------__+ TTL Vee or system VeeSystem ...--t--.........battery+ C,;;:..=-+-_r--~-~~---t___+ CMOS Vee-=-Ni-Cad1500mAHFig. 55V4.5~ Determined by CTCT = C2 + (another decoupling capacitor)..:.. BatteryI3VCE? 3VGNDt=O2.5V'1------- Example.3V? 2.0V'i------- CMOS Vee-0.1 - 0.2V? 1.5VrnFig_ 6455