Hi there.
While reading the Art Of Electronics (3rd edition) I looked at the nice circuit at page 467,
fig. 7.65 using an
ltc6991 and some other components to create an "automatic shutdown" of the circuit after one hour from its power up.
I thought that was neat and tried doing my own version, only to make it go for half an hour. Only my circuit does not work at all. So, after three days of trial and failure I came here for support.
Here's what I have different:
- Instead of the LVC2G02 I have connected two NORs from a 74HC02N I had around
- Instead of the LVC1G04 I used one inverter from a 74HC04 I had around
- I used a 1M resistor as R5 (as suggested in the LTC datasheet) accurately measured among the ones I have
- I connected 880K of resistance, accurately measured (680k+ 2*100K series) as R4 – note that this is a measure I adopted in the later stages of the circuit, since nothing else worked – in order to be as much compliant to the datasheet as possible
- calculated and put in an 82K resistor as R3 to achieve my result
- used a different p-fet, an IRLIB9343 which is the only p-fet I had around
- hooked up an LED to the fet drain to see when the cycle is through
Well after all of that the result is that well after 40~50 minutes, the circuit is still on and does not want to switch off!
Do you think I made any mistakes? If you think I should post images about what I did, I'll pretty 'em up and do it when I can (it's night here unfortunately).
Thanks to anyone even only for reading this