DAC38RF87: IS VCO frequency lower than sample rate OK?

Kei Kuwahara

Part Number: DAC38RF87
Other Parts Discussed in Thread: LMX2582

Tool/software:

Hello team,

My customer is wondering that VCO center frequency is only up to 5.9GHz, but DAC38RF87 can operate in 6.2GSPS.
How can a DAC operate faster than internal clock?

Best Regards,
Kei Kuwahara

4 months ago

0 Kang Hsia 4 months ago

TI__Guru 72239 points

Kei-san,

If the customer chooses to use external clocking (i.e. with LMX2582), they can use the DAC38RF87 all the way to 6.2GSPS.

-Kang

0 Kei Kuwahara 4 months ago in reply to Kang Hsia

TI__Expert 6090 points

Hello Kang-san,

I am still confused.

LMX2582 can output only up to 5.5GHz.

My understanding is that, if you want to operate DAC38RF87 in 6.2GSPS, then external clock should be 6.2GHz. Is this correct?

Best Regards,
Kei Kuwahara

+1 Kang Hsia 4 months ago in reply to Kei Kuwahara

TI__Guru 72239 points

Kei Kuwahara said:
My understanding is that, if you want to operate DAC38RF87 in 6.2GSPS, then external clock should be 6.2GHz. Is this correct?

Kei-san,

Yes, correct.

0 Kei Kuwahara 4 months ago in reply to Kang Hsia

TI__Expert 6090 points

Hello Kang-san,

The customer would like to operate this device in 4GSPS.

The internal VCO range is between 5240 - 6720MHz.

Can internal PLL and VCO create 4GHz?
OR should they use external clock source?

Best Regards,
Kei Kuwahara

+1 Kang Hsia 4 months ago in reply to Kei Kuwahara

TI__Guru 72239 points

Hi Kei-san,

They will need to use external clock. The internal VCO do not have the range to support 4GSPS.

Also, Dalton Stringer had reached out to you. Please check his proposal. He is on the HSC team and can support your customers more efficiently as their product line has a dedicated T&M focus.

-Kang

RF & microwave

RF & microwave forum

DAC38RF87: IS VCO frequency lower than sample rate OK?