CDCM6208: Can the crystal resonator, DSX321G(25MHz) be used for CDCM6208V1?

Kazuya Nakai59

Guru 21505 points

Part Number: CDCM6208
Other Parts Discussed in Thread: TMS320C6652,

Hello guys,

One of my customers is considering using CDCM6208V1 as the clock source for TMS320C6652.

They have a few questions as the follows. Could you please give me your reply?

Q1. Can the following crystal resonator, DSX321G(25MHz) be used for CDCM6208V1?

DSX321G

www.kds.info/.../

Q2. If Q1 answer is yes, do you have any design procedure for peripheral parts

(especially capacitor and resistor)?

Your reply would be much appreciated.

Best regards,

Kazuya.

over 4 years ago

0 Hao Z over 4 years ago

TI__Mastermind 18070 points

Hi Kazuya,

Yes this XTAL should be fine. No resistor is needed. For this device, you can assume 12pF of internal + PCB load capacitance (single ended) to start with. For example, if you choose 8pF load cap XTAL, then that means you need 16pF on each side. 16 - 12 = 4pF so you can place 4pF on both P and N now. Similarly, if you choose the 12pF load cap version, then place 24 - 12 = 12pF on each side. You can refer to below app note for more background knowledge on XTAL

https://www.ti.com/lit/ds/symlink/cdce6214-q1.pdf?ts=1615256545432&ref_url=https%253A%252F%252Fwww.google.com%252F

Regards,
Hao

0 Kazuya Nakai59 over 4 years ago in reply to Hao Z

Guru 21505 points

Hi Hao,

Thank you very much for your reply.

Could I ask you the following additional questions?

Q1. Is the app note you mentioned the follow?

https://www.ti.com/lit/an/snaa331/snaa331.pdf

Q2. Should they use equation 6 in the app note?

Q3. What is Cint_L1 of the equation 6 in case of CDCM6208V1?

Is it 7.25pF or 7.34pF as typical value?

Q4. The customer uses the secondary clock only. In the case, how treat is the primary input?

Could you please give me your reply?

Thank you again and best regards,

Kazuya.

0 Hao Z over 4 years ago in reply to Kazuya Nakai59

TI__Mastermind 18070 points

Hi Kazuya,

Yes that is the right appnote and you can use equation 6.

Yes you can use those values for internal load cap.

You can keep PRIREF floating if it's unused.

Regards,
Hao

0 Kazuya Nakai59 over 4 years ago in reply to Hao Z

Guru 21505 points

Hi Hao,

Could I ask you one more question?

If the customer use PRIREF not SECREF, can SEC_REFP and SEC_REFN be left open (floating) as same as PRIREF case?

Thank you very much and best regards,

Kazuya.

0 Aaron Black over 4 years ago in reply to Kazuya Nakai59

TI__Genius 11800 points

Hello Kazuya,

Yes, Inputs if unused in general should be left floating.

Clock & timing

Clock & timing forum

CDCM6208: Can the crystal resonator, DSX321G(25MHz) be used for CDCM6208V1?