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

 

[John Fields]

On Thu, 05 Jul 2007 05:22:15 -0700, RichardJHarris2@gmail.com 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.


--
JF

 

[John Fields]

On Thu, 05 Jul 2007 08:18:41 -0500, John Fields
<jfields@austininstruments.com> wrote:

On Thu, 05 Jul 2007 05:22:15 -0700, RichardJHarris2@gmail.com 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

 

On 5 Jul, 14:20, John Fields <jfie...@austininstruments.com> wrote:

On Thu, 05 Jul 2007 08:18:41 -0500, John Fields



jfie...@austininstruments.com> wrote:
On Thu, 05 Jul 2007 05:22:15 -0700, RichardJHarr...@gmail.com 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