Linux/BQ32002: RTC time lag

Deepanraj Anbarasan

Expert 1140 points

Part Number: BQ32002

Tool/software: Linux

Hi,

Please let us know, the formula to convert ppm from frequency.

Thank you,

Deepanraj

over 7 years ago

0 Lane Boyd over 7 years ago

TI__Genius 16845 points

Hi Deepanraj,

For speeding (S=1), the formula is:
Offset [ppm] = - CAL *1e6 / 245760 = - CAL / 4.069

For slowing (S=0), the formula is:
Offset [ppm] = +CAL * 1e6 / 491520 = + CAL / 2.035

See datasheet Tables 11 & 12 for more information.

Kind regards,
Lane

0 Deepanraj Anbarasan over 7 years ago in reply to Lane Boyd

Expert 1140 points

Hi Lane,

Please let us know the same calibration value can be used if the crystal for the lot are same for all the devices.

Or will the ppm value change for each of the board with respect to temperature.

Thank you,

Deepanraj.A

0 Deepanraj Anbarasan over 7 years ago in reply to Lane Boyd

Expert 1140 points

Hi Lane,

During mass production it will be difficult to calibrate each board for the RTC. So please let us know is there any software tool available to calibrate across the RTC during mass production.

Thank you,
Deepanraj

0 Deepanraj Anbarasan over 7 years ago in reply to Lane Boyd

Expert 1140 points

Hi Lane,

Please update us on the above queries.

Thank you,

Deepanraj.A

0 Dean Banerjee over 7 years ago in reply to Deepanraj Anbarasan

TI__Mastermind 28031 points

Deepanraj,

I'm not the expert on this device, but it seems to me that the ppm adjustment should be very similar for devices from the same lot. But depending on your expectations for frequency accuracy, it would seem that at some point, part specific might be necessary.

Lane is out this week on vacation, but will be back next week and maybe he has more to add.

Regards,
Dean

0 Deepanraj Anbarasan over 7 years ago in reply to Dean Banerjee

Expert 1140 points

Hi,

Please let us know the below query,

We will configure the IRQ bit to 1Hz.is it possible to read the frequency of the IRQ and correct the error through software.

so that it will easy for us to calibrate the device during mass production.

0 Dean Banerjee over 7 years ago in reply to Deepanraj Anbarasan

TI__Mastermind 28031 points

Hi,
I can't answer this, but we have several members of our team on vacation next week, so I am hoping that someone else can.
Regards,
Dean

0 Lane Boyd over 7 years ago in reply to Dean Banerjee

TI__Genius 16845 points

Hi Deepanraj,

Thanks for your patience. No, it is not possible to read the frequency through software; you must use measurement equipment. I highly recommend to use a precision frequency counter for calibration.

Kind regards,
Lane

0 Deepanraj Anbarasan over 7 years ago in reply to Lane Boyd

Expert 1140 points

Hi Lane,

Can you please let us know, How to calculate the ppm value from the delay.

For example:

if we are getting 5 secs delay in time what is the ppm value to be calculated.Is there any formula to calculate ppm from the seconds

Thank you,

Deepanraj

Clock & timing

Clock & timing forum

Linux/BQ32002: RTC time lag