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Visitor II
March 30, 2022
Solved

Why do we choose LSE capacitance low?

  • March 30, 2022
  • 1 reply
  • 2087 views

STM32H7B3I-DK - Discovery kit use NX3215SA-32.768KHZ-EXS00A-MU00525 Crystal. Crystal Load Capacitance is 6, 9, 12.5 pF but STM32H7B3I-DK - Discovery kit use 1.5pF. Why it use different load capacitance.

0693W00000LwI0nQAF.png

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    Best answer by Freedom_Neo

    First, you must be sure that your crystal is compatible with the selected STM32 LSE. Then, it is highly recommended to use a crystal with low pullability, that is with CL ≥ 6 pF:

    7 pF is a good compromise between low drift and moderate power consumption

    9 and 12.5 pF can be used in noisy environments, but impact the power consumption.

    1 reply

    Graduate II
    March 30, 2022

    > Read AN2867.

    Which part of this sentence from the previous topic you do not understand?

    Freedom_NeoAuthorAnswer
    Visitor II
    March 30, 2022

    First, you must be sure that your crystal is compatible with the selected STM32 LSE. Then, it is highly recommended to use a crystal with low pullability, that is with CL ≥ 6 pF:

    7 pF is a good compromise between low drift and moderate power consumption

    9 and 12.5 pF can be used in noisy environments, but impact the power consumption.

    Graduate II
    March 30, 2022

    That quote doesn't even answer your question about the capacitors.

    I'll tell you a secret - to understand a load capacitance, you should at least read the section called "Load capacitance"!