LMX2572EVM: In case of FSK=Enable

Hi all

We guess that your days are so busy and your environment might not be happy.
However if you have some update could you let us know?

Kind regards,

Hirotaka Matsumoto

Noel san

Thank you so much for your reply!

The problem you have is you are trying to do a delta F of 62.2MHz.
This is not possible with the FSK function because the VCO will have to change its frequency by 124.4MHz.
This VCO frequency change is only possible with a VCO calibration. However, FSK does not do VCO calibration.
That's why you are not getting a correct output frequency.
->We got that the VCO will have to change its frequency by 124.4MHz in case of FSK function.
   Could you inform us the precedure with correct output frequency by 124.4MHz?
   FSK doesn't do VCO calibration, so how much of VCO's frequency does it use for FSK function?

Kind regards,

Hirotaka Matsumoto

Hi Matsumoto-san,

If deltaF of 124.4Mhz is required, you can use manual ramp and ramp between fo and fo + 124.4MHz. Ramp mode supports VCO calibration. Check datasheet section 8.1.7.1 for details.

Noel san

Thank you so much for your cooperation always!

We got that the problem is that we are trying to do a delta F of 62.2MHz.
And we also understand we have to choice the lower value of FSK_SPI_FAST_DEV.
So, we would like to confirm you two points finally.

<Question1>
How much is the range which VCO can do calibraton?
We understand that 62.2MHz is bigger, so we would like to know suitable value.

<Question2>
We would like to calculation formula.
If FSK_SPI_FAST_DEV is 1, how much will be the output frequnecy?

Kind regards,

Hirotaka Matsumoto

62.2MHz

Noel san

Thank you so much for your cooperation always.

And then, we are sorry that our explanation makes confuse you.

We would like to ask you about <Question1> and <Question2>.

What we would like to confirm on <Question1> is follow;
I suspect that, in FSK mode, if the frequency shift is small, the VCO calibration may not be necessary.
If it is true, how much frequency offset can the device be operational without VCO calibration?

What we would like to confirm on <Question2> is follow;
On the dault setting, if FSK_SPI_FAST_DEV increase +1, how much will the output frequency be?

Kind regards,

Hirotaka Matsumoto

Noel san

Thank you so much for your reply always!

We got it.
Just in case, we would like to confirm one point whether our recognition is correct or not.

On the default EVM setting;
fPDx=100MHz
2^FSK_DEV_SCALE=1
/ PLL_DEN =1000
/ CHDIV=1
delta F = 1 x fPD x 2^FSK_DEV_SCALE / PLL_DEN / CHDIV
->Δf=100kHz
In this case, this Δf is within the calibration's tunable range.

In case of 2^FSK_DEV_SCALE=662;
delta F = 1 x fPD x 2^FSK_DEV_SCALE / PLL_DEN / CHDIV
->Δf=66.2MHz
In this case, this Δf may be within of the calibration's tunable range. However, this value is no recommended tunable range.

Kind regards,

Hirotaka Matsumoto