Where can I get the most up-to-date information on PSOC5lp clock accuracy ? I see AN80248 is obsolete but why ? Is there a follow-up ?

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pacr_284376
Level 5
Level 5
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I need to have more information on clock accuracy. In the past I used AN80248 for details but this document is now marked as OBSOLETE.

In my design I have no external clock. What is the best possible accuracy when using :

* USB port

* No USB port

Thanks

Patrick

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1 Solution
brockr0-S
Level 4
Level 4
First like received Welcome!

Updated information for IMO is available here <https://www.cypress.com/documentation/code-examples/ce219322-psoc-3-and-psoc-5lp-internal-main-osc...

ILO here <https://www.cypress.com/documentation/component-datasheets/ilo-trim >

From the family datasheets ILO accuracy for 24 MHz - non-USB mode is +/- 4%..

Accuracy for 24 MHz USB mode with oscillator locking to USB bus is +/- 0.25%.

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brockr0-S
Level 4
Level 4
First like received Welcome!

Updated information for IMO is available here <https://www.cypress.com/documentation/code-examples/ce219322-psoc-3-and-psoc-5lp-internal-main-osc...

ILO here <https://www.cypress.com/documentation/component-datasheets/ilo-trim >

From the family datasheets ILO accuracy for 24 MHz - non-USB mode is +/- 4%..

Accuracy for 24 MHz USB mode with oscillator locking to USB bus is +/- 0.25%.

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I see now AN80248 is indeed replaced by 002-19322 (=CE219322)

Thanks for this answer.

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I found this article useful.  It addresses clock tolerance for USB with 5LP external crystal added.

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Brock,

Yes, the 24MHz USB mode with the oscillator locking to the USB can achieve +/- 0.25% accuracy.  But this assumes the USB is connected to the PC and the PC is providing a 48MHz reference clock from its USB.  If the USB is disconnected or the PC is powered down and the power to the PSoC is not via USB, then the external reference clock is missing and the IMO will at best favor a +/- 4% tolerance.  Maybe someone from Cypress can weigh in on this.

Len

Len
"Engineering is an Art. The Art of Compromise."
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