Part Number: SN74LV123A
Hello Experts,
My customer would like to design 1 sec timer by SN74LV123A. Customer tested the device almost 1 sec timer, using RT=100Kohm/CT=10uF. Customer got a good result but customer would like to know whether it is a reasonable value for RT and CT. Or do you have any recommendation?
Cext and Cext/Rext terminals have ESD protection diode inside the chip, correct?
Best Regards,
Fujiwara
Hello Fujiwara-san,
Yes, the Cext and Cext/Rext terminals do have internal ESD protection.
The capacitor value is not limited, so 10 μF is no problem.
The resistor value will depend on the temperature range of operation. The leakage value given is 2.5 μA for up to 85C, or 25 μA for up to 125C:
There is no problem with using 100 kΩ for RT up to 85C. However, I would recommend to keep RT less than 20 kΩ for operation up to 125C. This is to keep the leakage current from producing too much of a voltage drop across the resistor at high temperatures and under some possible process variations.
