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PSoC™ 4 Forum Discussions

ToKi_1339406
Level 2
Level 2
10 questions asked 5 replies posted 5 questions asked

Regarding, the CY8CKIT-142 PSoC 4 BLE Module Schematic.pdf, looking at the psoc 4 ble module schematic as attached, the values ​​of load cap C23 and C24 at 32.768KHz are 36pF and 18pF, so I'm wondering why used it differently, although I generally know by using the same load cap value.

Thank you!

Tony Kim

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1 Solution
VenkataD_41
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi Tony Kim,

A higher C1/C2 ratio results in a higher current consumption but improved duty cycle. Based on extensive characterization, a ratio of 2:1 (C1= 2×C2) for the external capacitors is found to be optimal with respect to the performance and power consumption. The tradeoff for using a 2:1 ratio is slightly higher ICC (Integrated Chip Current) of up to 100 nA. For a 2:1 ratio, the recommended external capacitor values are: C1 = 37.5 pF, C2 = 18.75 pF (for CL = 12.5 pF) C1 = 18 pF, C2 = 9 pF (for CL = 6 pF).

For more information, please go through the following application note:

https://www.cypress.com/documentation/application-notes/an95089-psoc-4proc-ble-crystal-oscillator-se...

Thanks

Ganesh

View solution in original post

1 Reply
VenkataD_41
Moderator
Moderator
Moderator
750 replies posted 500 replies posted 250 solutions authored

Hi Tony Kim,

A higher C1/C2 ratio results in a higher current consumption but improved duty cycle. Based on extensive characterization, a ratio of 2:1 (C1= 2×C2) for the external capacitors is found to be optimal with respect to the performance and power consumption. The tradeoff for using a 2:1 ratio is slightly higher ICC (Integrated Chip Current) of up to 100 nA. For a 2:1 ratio, the recommended external capacitor values are: C1 = 37.5 pF, C2 = 18.75 pF (for CL = 12.5 pF) C1 = 18 pF, C2 = 9 pF (for CL = 6 pF).

For more information, please go through the following application note:

https://www.cypress.com/documentation/application-notes/an95089-psoc-4proc-ble-crystal-oscillator-se...

Thanks

Ganesh