I have a RTC base on DS1302, problem is it have drift 1 min/week which is not acceptable.
I know I need a high accuracy crystal 32khz to solve this problem.
How I choose which crystal? There is a parameter +/-ppm on the freq accurate.
What does +/- ppm mean? If I only allow 1 seconds/week drift or better, what ppm I need?
Or is there any method I can keep the RTC run accurately?
Btw, the RTC DS1302 is link to a PIC and display on LCD, running on room temp 25~30degC.
I know I need a high accuracy crystal 32khz to solve this problem.
How I choose which crystal? There is a parameter +/-ppm on the freq accurate.
What does +/- ppm mean? If I only allow 1 seconds/week drift or better, what ppm I need?
Or is there any method I can keep the RTC run accurately?
Btw, the RTC DS1302 is link to a PIC and display on LCD, running on room temp 25~30degC.