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#1
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frequency precision
Have a kind of difficult question.
im looking for RTC chips for a micro controller project, i need an accurat way of keeping time as well as interrupt alarms and can use I2C or SPI for the application, my problem is understanding the precision of these chips from there technical specification. For example the sheet http://www.rapidonline.com/netalogue/specs/90-0398.pdf Page 4, frequency characteristics shows 5 +- 23 * 10^-6. Just exaclty how does one interpret this? Any help is much appreciated. Thanks for your time Richard |
#3
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frequency precision
On Thu, 05 Jul 2007 08:18:41 -0500, John Fields
wrote: On Thu, 05 Jul 2007 05:22:15 -0700, wrote: Have a kind of difficult question. im looking for RTC chips for a micro controller project, i need an accurat way of keeping time as well as interrupt alarms and can use I2C or SPI for the application, my problem is understanding the precision of these chips from there technical specification. For example the sheet http://www.rapidonline.com/netalogue/specs/90-0398.pdf Page 4, frequency characteristics shows 5 +- 23 * 10^-6. Just exaclty how does one interpret this? --- That means that the oscillator frequency can be anywhere between 32768Hz + 28ppm and 32768Hz - 18ppm. That is, anywhere between 32768.9175Hz and 32767.4102Hz. --- With a Vdd of 3.0V and an ambient temp of 25C. -- JF |
#4
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frequency precision
On 5 Jul, 14:20, John Fields wrote:
On Thu, 05 Jul 2007 08:18:41 -0500, John Fields wrote: On Thu, 05 Jul 2007 05:22:15 -0700, wrote: Have a kind of difficult question. im looking for RTC chips for a micro controller project, i need an accurat way of keeping time as well as interrupt alarms and can use I2C or SPI for the application, my problem is understanding the precision of these chips from there technical specification. For example the sheethttp://www.rapidonline.com/netalogue/specs/90-0398.pdf Page 4, frequency characteristics shows 5 +- 23 * 10^-6. Just exaclty how does one interpret this? --- That means that the oscillator frequency can be anywhere between 32768Hz + 28ppm and 32768Hz - 18ppm. That is, anywhere between 32768.9175Hz and 32767.4102Hz. --- With a Vdd of 3.0V and an ambient temp of 25C. -- JF Thanks very much, got it now |
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