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AD9910 crystal clock input

Question asked by harrycheung on Dec 11, 2012
Latest reply on Dec 17, 2012 by KennyG

Question 1)

I am using a TCXO (see attached) as the crystal REF_CLK input for AD9910. A passive crystal is used the evaluation board schematic, but the TCXO is a powered crystal. Do I need to change the suggested connection (a 39pF capacitor at each end of the crystal) to another connection?

 

Question 2)

The TXCO is a 26 MHz crystal with a 0.8 Vpp clipped sinewave output. Is it necessary to convert it to a square or sine output before feeding in the AD9910? If yes, how can I do it?

 

Question 3)

For AD9910 with crystal reference clock, should I enable the PLL multiplier (N) and set N = 40 to get a 1.04 GHz internal clock frequency? Also, should the VCO range be set at VCO5 ( 820 - 1150 MHz)?

 

Question 4)

For the PLL loop filter, what does the loop bandwidth (f_OL) represent? The datasheet gives a formula for the loop filter parameters (p.27) based on  the gain of phase detector (K_D) and gain of the VCO (K_V). How will K_D and K_V change the performance of the PLL loop filter?

 

P.S.

I found pin 2 (PLL_LOOP_FILTER) and pin 3 (AVDD(1.8V)) to be internally connected, is it normal?

 

Thanks

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