AN199
Rev0.7 | 4
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Table 3. Correspondence between PLL Analysis Parameters and Target Frequencies
Target Frequency Band
FREQ_DIVX_CODE <2:0>
DIVIDER
FREQ_VCO_BANK<2:0> = 110
FREQ_VCO_BANK<2:0> = 001
758
– 840 MHz
840
– 1020 MHz
000
2
379
– 420 MHz
420
– 510 MHz
001
4
189.5
– 210 MHz
210
– 255 MHz
010
8
126.33
– 140 MHz
140
– 170 MHz
011
12
252.67
– 280 MHz
280
– 340 MHz
101
6
Then calculate the frequency of the LO (local oscillator). In the formula below, FREQ_RF is the target RF frequency in MHz.
FREQ_LO is the calculated local oscillator frequency in Hz.
FREQ_LO = FREQ_RF x 10^6 + 26 MHz/92
Then calculate the value of the frequency word N.K.
N.K = FREQ_LO x DIVIDER / 26 MHz
Obtain the integer part of N.K and convert it to binary, which is the value of FREQ_RX_N <7:0>. The fractional part is multiplied
by 2^20 and rounded off
,
which is the value of the register FREQ_RX_K <19:0>.
The last step is to get the value of AFC_OVF_TH <7:0>. This register is not in the frequency area. As an key parameter of the
receiver AFC algorithm, it is calculated based on such parameters of receivers as RX RF frequency, data rate, deviation, and
crystal PPM. When the calculation completes, the result displays on the RFPDK screen as shown in the below figure.
