Igor Orlovich

LSE oscillator: board parasitics and low load capacitance?

Discussion created by Igor Orlovich on Sep 26, 2017

Going by AN2867 for STM32L0 parts, I've selected a few crystals with 4pF load capacitance (based on size, price and availability). The question is, what do I assume board and chip parasitics to be when figuring out load caps? The 10pF number listed in datasheet is too large to be able to have two load caps in series plus parasitics all matching the 4pF load figure. LSE input pin is listed as 0.6pF, so do I assume something like a few puffs and use 4pF load caps, or go all the way up to 9-12pF load and risk oscillator startup issues?

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