Audioguru, I'm aware of the specs of the battery in terms of the current restrictions. It's 3V @ 0.130mAh. I'm talking about pulling <10 microamps out of it. Not 190uA.
Just because the batteries discharge curve is spec'd at 190uA doesn't mean I have to go anywhere near that.
I'd like to pull the quiescent current of the ICs out of it without nuking some components which are 6v rated before the batteries start to deplete below 3v/piece, and in turn conserve battery life.
Richard
How many of these circuits are you going to make?
Is it commercial, automotive, defence, a one off and/or a hobby/college project? Will it be operated at high temperatures? Are other parameters being pushed to their limits, i.e. operating frequency, output current?
All of the ICs you've listed have an absolute maximum rating or 7V. They may not be guaranteed to operate properly at this voltage, over the full temperature range, but they should be able to withstand it for short periods of time, without damage. They're designed to operate properly up to 6V, at 125
oC, with no problems. It's pretty safe to say that operating at 125
oC, at 6V will be far more stressful to the IC, than 30
oC at 6.4V. Look at the table for the 74HC1G00, on the bottom left hand of page 2 the data sheet "DEVICE JUNCTION TEMPERATURE VERSUS TIME TO 0.1% BOND FAILURES". I'd be more worried about high temperatures, than slightly higher supply voltages, than recommended on the data sheet.
https://www.onsemi.com/pub/Collateral/MC74HC1G00-D.PDFThere's a myth going round that components automatically let out magic smoke, when their maximum operating specifications are exceeded. This is total nonsense. Whilst it's good design practise to not exceed maximum operating specifications and shouldn't be done lightly, it doesn't mean it shall never happen. The main risk is that reliability will be compromised, which can be a huge problem in a volume manufactured product, especially if it's operated in an adverse environment i.e. high operating temperature, but if you're only making a few, the components aren't being pushed to their other design limits, a slight over-voltage is no problem.
In short, if the components are run at room temperature, a low output current and you're only making a few, then don't worry about using a supply voltage of 6.4V, especially if it's just a hobby project. It's not worth trying to lower the voltage by 0.4V. All it will do is shorten the life of the batteries and add more components which could cause other problems.