ECO Load Capacitance Specification

[Anonymous]

Am having trouble sourcing the 24MHz ECO I have been using in my Production of PSoC4 BLE devices (we've been using the ECS-240-8-36CKM part), so am looking at alternatives.

   

In the spec document that Cypress have put out for Crystal Oscillator selection and tuning (AN95089), they list a number of key specs for the ECO.  One of these is that the load capacitance be 8pF.

   

Does anyone know how critical that value is?  I can find a heap of suitable ECO's, but they all have a load capacitance figure of 10pF.  Is that going to totally bugger my RF performance?  Or is it something I can tune out easily enough?

   

Cheers,

   

Mike

[Anonymous · Accepted solution]

Hi Mike,

   

Yes, it is highly recommended that the load capacitance of the selected crystal is 8 pF.

   

As you know, the  oscillator of PSoC4/PRoC BLE devices is designed to work with  8-pF load capacitance, which requires that the chosen crystal has 8-pF load capacitance.

   

But you can also tune the internal load caps to 10 pF for your 10 pf crystal using "Crystal Tuning Technique for ECO" explained in the AN. Upto 10 pF should not create much RF issues.