73M1903C-EVM Maxim Integrated Products, 73M1903C-EVM Datasheet - Page 45

• Manufacturer Part Number: 73M1903C-EVM
• Description: BOARD DEMO 73M1903C WORLDWIDE
• Manufacturer: Maxim Integrated Products

Specifications of 73M1903C-EVM

• Main Purpose: Interface, Analog Front End (AFE)
• Utilized Ic / Part: *
• Primary Attributes: *
• Secondary Attributes: *
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Embedded: -

DS_1903C_033
73M1903C Data Sheet
, where Nnco1 and Nnco2 must be < or equal to 8.
The ratio, Nnco1/Dnco1 = 1/7, is used to form a divide ratio for the NCO in prescaler and Nnco2/Dnco2 =
1/18 for the NCO in the PLL.
Prescaler NCO: From Nnco1/Dnco1 = 1/7,
Pdvsr = Integer [nco1/Nnco1] = 7;
Prst[2:0] = Nnco1 – 1 = 0; this means NO fractional divide. It always does ÷7. Thus Pseq becomes
“don’t care” and is ignored,
Pseq = {x,x,x,x,x,x,x,x} = xxh.
PLL NCO: From Nnco2/Dnco2 = 1/18,
Ndvsr = Integer [Dnco2/Nnco2] = 18;
Nrst[2:0] = Nnco2 – 1 = 0; this means NO fractional divide. It always does ÷18. Thus, Pseq becomes
“don’t care” and is ignored.
Nseq = {x,x,x,x,x,x,x,x} = xxh.
Example 2
Crystal Frequency = 24.576 MHz; Desired Sampling Rate, Fs = 10.971 kHz=2.4 kHz x 8/7 x4
Step 1. First compute the required VCO frequency, Fvco, corresponding to
Fs = 2.4 kHz x 8/7 x 4 =10.971 kHz.
Fvco = 2 x 2304 x Fs = 2 x 2304 x 2.4 kHz x 8/7 x 4 = 50.55634 MHz.
Step 2. Express the required VCO frequency divided by the Crystal Frequency as a ratio of two integers.
This is initially given by :
•
•
•
•
2
2304
2.4kHz
8/7
4
=
.
Fvco
/
Fxtal
24
.
576
MHz
Rev. 5.0
45