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Errata 146 of nRF52832

Remo

Hi all

According to errata 146 of the nRF52832 Rev 1 errata sheet V1.5, the LFRC oscillator has a frequency tolerance of 500ppm instead of 250ppm.

What are the consequences of this errata regarding the BLE stack? Does this mean that the LF RC oscillator cannot be used anymore for the SoftDevice? By the way, I'm using the S132 V2.0.1.

The product specification states that the required frequency tolerance for the BLE stack is 250ppm (fTOL_LFXO_BLE)!

Many thanks in advance!

Kind regards

  • FormerMember
    0 FormerMember

    At some, very few nRF52832 devices, the frequency tolerance of the RC oscillator may/will exceed +/- 250 ppm. For the affected devices, the result is larger a packet loss rate, which can lead to a disconnect.

    For S132 v.2.0.1 with the RC oscillator, it is only possible to set the LFCLK accuracy to +/- 250 ppm. If you experience that most of the devices work fine, but a very few of the devices exhibit a disconnect problem, those very few devices are most likely affected by Errata 146.

    If you can live with having a few devices where the RC oscillator exceeds +/- 250 ppm, there shouldn't be any problem continue using the RC oscillator with a +/- 250 ppm setting.

    For BLE, the sleep clock accuracy should be within +/- 500 ppm (BT Core specification v.5.0, Vol 6, Part B, chapter 4.2.2).

  • 0 in reply to FormerMember

    Thank you for your response. I cannot live with that some devices would always lead to link terminations. This would be a worst-case scenario for us! Therefore, I have some further questions to clear things up a bit:

    1. How many percent are "some very few devices"?
    2. What calibration interval is necessary to mask this problem?
    3. This means that the accuracy is never 500ppm directly after a calibration?
    4. Why does Nordic state that for the BLE stack an accuracy of 250ppm is necessary while the BT core specification requires 500ppm?
  • FormerMember
    0 FormerMember in reply to FormerMember

    1) Unfortunately, I cannot comment on this one.

    2) It's not possible to mask this problem fully other than to update to a softdevice that support 500ppm tolerance for the RC clock.

    3) Unfortunately, I cannot comment on this one.

    4) The latest version of the softdevice should have an option for setting the RC-oscillator frequency accuracy to +/- 500 ppm

  • 0 in reply to FormerMember

    Thanks for your answer.

    I've got one last question just to be sure that I understood it correctly. When I use S132 V2.0.1 there may be some link terminations because the SD expects a LF RC oscillator accuracy of 250ppm instead of 500ppm, but when I would use S132 V4.0.3 and specify the RCOSC accuracy to 500ppm there will be NO problem. Is this correct?

  • FormerMember
    0 FormerMember in reply to FormerMember

    Yes, that's correct! When using S132 v.4.0.0 and specify the RCOSC accuracy to 500 ppm, the RCOSC should not cause any linkloss.

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