LMK04803BEVAL: regarding the crystek VCXO

Maitry Khambhati

Part Number: LMK04803BEVAL
Other Parts Discussed in Thread: LMK04803, LMK6C

Hello support team,

I have finalized LMK04803 with the PLL2 VCXO frequency =60 MHz to finally generate 110 MHz. but as I see that crystek VCXO is not available, could you please provide another alternate to crystek VCXO that we can use at the input of PLL2 ?

over 3 years ago

0 Connor Lewis over 3 years ago

TI__Genius 13250 points

Hi Maitry,

The LMK6C family can be used in some applications as a crystal replacement, but we do not offer an alternative VCXO at this time.

Regards,

Connor

0 Maitry Khambhati over 3 years ago in reply to Connor Lewis

Intellectual 450 points

Hello,

Thank you for the response.

But, LMK6C is also not available in the stock.

0 Connor Lewis over 3 years ago in reply to Maitry Khambhati

TI__Genius 13250 points

Hi Maitry,

We are planning on launching some fixed-frequency variants of LMK6C by the end of the year. Unfortunately, at this time we don't have VCXOs planned for production.

Regards,

Connor

0 Maitry Khambhati over 3 years ago in reply to Connor Lewis

Intellectual 450 points

Hello Connor,

Is there any specific phase noise performance requirement for the VCXO for LMK04803 to generate low jitter output? based on that, we will finalize the commercial available VCXO.

0 Connor Lewis over 3 years ago in reply to Maitry Khambhati

TI__Genius 13250 points

Hi Maitry,

I don't believe there is a specific VCXO phase noise requirement, but the output jitter measurements provided in the datasheet were taken with a Crystek CVHD-950-122.880 VCXO, which has the following phase noise performance at 100 MHz:

1 KHz	-140 dBc/Hz
10 KHz	-155 dBc/Hz
100 KHz	-164 dBc/Hz
1 MHz	-166 dBc/Hz

Since the external VCXO is mainly used to remove noise within a 50 KHz offset, the low frequency performance is more meaningful than RMS jitter which has a wider integration range. This thread has some more details about configuring the PLL bandwidth to optimize output jitter: https://e2e.ti.com/support/clock-timing-group/clock-and-timing/f/clock-timing-forum/259167/lmk048-detailed-performance

Note that we also have a tool called PLLatinum sim that allows you to estimate the output jitter given the input, PLL, and VCXO noise to see if it meets your design requirements.

Regards,

Connor

0 Maitry Khambhati over 3 years ago in reply to Connor Lewis

Intellectual 450 points

Hello,

Thank you for the response.

Actually, we are facing issue for unavailability of the VCXO that can be used with LMK04803. As we want to generate 110 MHz LVCMOS output from LMK04803.

So, the required freq. for external VCXO would be : 20, 30,55,60 MHz. all are standard freq. still we are not getting commercial VCXO for the same. So, if TI can support anything alternate that we can use instead of commercial VCXO with LMK04803 , then it would be helpful.

0 Connor Lewis over 3 years ago in reply to Maitry Khambhati

TI__Genius 13250 points

Hi Maitry,

Unfortunately, we don't have any other recommendations for VCXOs at this time.

Regards,

Connor

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LMK04803BEVAL: regarding the crystek VCXO