eefelix
Junior Member level 1
eefelix
Hello everyone,
Recently I've a real time clock project, the objective is to generate an accurate 1Hz output using 32768Hz crystal.
At first I think it's a simple project, all I've to do is to create a 15-bit prescaler circuit ( 32768/(2^15)=1Hz ).
The problem is: our customer want to include a digital circuit to fine-tune the output frequency that may due to the environment variation impacting the crystal frequency. What's more they want the circuit to generate 1024Hz test output to make fine-tunning faster.
Here's my questions:
- Typically how accurate is 32768Hz crystal (e.g. +/-1Hz ? +/-0.1Hz ?) ?
- Does the crystal accuracy affect much by environment (e.g. 32767Hz@-25C & 32769Hz@125C) ?
- Is it practical to generate 1024Hz test output for fine-tunning ? (e.g. if crystal freq. = 32769Hz, then test freq. = 1024.03Hz, that mean it require ~50sec. to detect this 1Hz crystal freq. variation. The situation even get worst when detecting smaller crystal freq. variation)
Pls. feel free to reply If you've any suggestion. Thanks!
Felix.
Hello everyone,
Recently I've a real time clock project, the objective is to generate an accurate 1Hz output using 32768Hz crystal.
At first I think it's a simple project, all I've to do is to create a 15-bit prescaler circuit ( 32768/(2^15)=1Hz ).
The problem is: our customer want to include a digital circuit to fine-tune the output frequency that may due to the environment variation impacting the crystal frequency. What's more they want the circuit to generate 1024Hz test output to make fine-tunning faster.
Here's my questions:
- Typically how accurate is 32768Hz crystal (e.g. +/-1Hz ? +/-0.1Hz ?) ?
- Does the crystal accuracy affect much by environment (e.g. 32767Hz@-25C & 32769Hz@125C) ?
- Is it practical to generate 1024Hz test output for fine-tunning ? (e.g. if crystal freq. = 32769Hz, then test freq. = 1024.03Hz, that mean it require ~50sec. to detect this 1Hz crystal freq. variation. The situation even get worst when detecting smaller crystal freq. variation)
Pls. feel free to reply If you've any suggestion. Thanks!
Felix.