I am using BNO055 chip for custom PCB module

I could not find a proper crystal oscillator for this ic for the given spec in the datasheet.

datasheet mention only 32.768Khz crystal oscillator with 22pF load capacitors

enter image description here

  • 1
    \$\begingroup\$ You are not looking for a crystal oscillator. You are just looking for a crystal. \$\endgroup\$
    – TimWescott
    Nov 13 '19 at 18:54
  • \$\begingroup\$ @TimWescott you mean crystal resonator or radial crystal will do the work? \$\endgroup\$
    – oppo
    Nov 16 '19 at 14:16
  • \$\begingroup\$ I'm not sure what you mean by "radial crystal", but that schematic signal in between the caps and the IC is a crystal (which I suppose is what you mean by "crystal resonator", but absolutely every English-speaking engineer in the word calls them "crystals" and has done so since 1920). \$\endgroup\$
    – TimWescott
    Nov 16 '19 at 21:35

This is mis-leading.

Their "load capacitors" are actually in series (with gnd.) in the circuit loop so their "Equivalent" Load Capacitance,(Ceq=1/2C) is one-half (1/2) of the C value. Then the IC input and trace capacitance to ground is summed to this Ceq to get the total or "Load Capacitance" the rating you will find on 32.768 kHz (or any ) Crystals.

So it seems they, Bosch are suggesting you choose a crystal rated for 12.5 pF with 1.5pF allotted for Cinput + stray. This implies you put the parts close to the pins and do not use a ground plane under the traces which adds a few pF but depends on details. (0.5pF/mm typ)

This is not the only choice as 12,11,10 pF is also avail,

Other common choices are 7 pF, 9 pF, which may be useful for reducing dynamic load dissipation in micropower applications.


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