I built the ubiquitous battery voltage monitor using the equally ubuiqutous LM3914. It monitors a 12V battery and controls a charger.
The datasheet mentions the IC can interface with TTL or CMOS logic, but I can't find how this is actually done anywhere. I want to do it properly.
Right now I connect the relevant IC's output pins to a 4013 Set/Reset flip-flop via a small-signal transistor, either a PNP or NPN to produce the required high and low signals for the CMOS. I also used small signal mosfets to the same effect.
However I feel the intermediary transistors are redundant. I tried direct connection to the flip-flop, and while the LM3914's output open state of course is at VCC, in the closed state (LED "on"), the output voltage is 9V, and if I undestand the datasheet correctly, the output is in fact a programmable current sink so this "low" voltage can vary with the programmed current. I feel this makes it hard to correctly interface with CMOS logic circuitry.
What am I missing? Many thanks in advance for insights. -Joe
Disclaimer: I am only a hobbyist but I think I have the basics down enough to undestand technical explanations.