LMX2572: Calculation of RAMP size for RAMPx_INC calculation in automatic ramping.

Vanshaj Kaistha

Part Number: LMX2572

Hi all,

I am trying to code the calculate of the RAMPx_INC for my device but i am not able to find the way how i can calculate the ramp size here.

I have considered the an example of calculating the ramp size that is: let's say the start freq is 3600 and end freq is 3700.

ramp size = efreq - sfreq, which makes ramp size 100.

Now if i try to calculatre the RAMPx_INC from the formula provided in the data sheet the output value varies. I verified it by putting the same value in the TICSpro.

Kindly, provide me the factors i am missing. Thanks

over 1 year ago

0 Noel Fung over 1 year ago

TI__Guru** 110330 points

Hi There,

You need to put fpd in your calculation.

Please also check the examples in the EVM user's guide.

0 Vanshaj Kaistha over 1 year ago in reply to Noel Fung

Prodigy 40 points

Hi noel, i concluded that how to calculate the RAMP_INC but what i actually need to know is that how we are calculatating the actual end freq in the automatic ramping mode. As i put the desired end freq to 6020 MHz and the actual end freq is 6020.02716064 MHz.

Here how we calculate the ramp size,

Delta freq = (Actual endFreq - Actual startFreq)/RampLen

+1 Noel Fung over 1 year ago in reply to Vanshaj Kaistha

TI__Guru** 110330 points

HI Vanshaj,

Ramp function requires PLL DEN = 2^32.

Given RAMP_INC is an rounded-off integer, the actual frequency increment is therefore not necessary be exactly equal to theory.

0 Vanshaj Kaistha over 1 year ago in reply to Noel Fung

Prodigy 40 points

Hi Noel, thanks for the input this clears my doubt for the ramp0 end freq but will it be same for the actual start freq as i will use RAMP1 for latter operations for my device.

Thanks.