U3600BM_05 Datasheet, PDF (21/44 Pages) ATMEL Corporation – Single-chip Cordless Telephone IC

U3600BM
10. Tables for Programming of the Dividers (Refer to Block Diagram)
Table 10-1. Divider D1 for PLL2
D11 (bit)
D10 (bit)
0
0
0
1
1
0
1
1
Decimally
0
1
2
3
D1 (Block Diagram),if M12 = 0
2
8
6
4
D1 (Block Diagram),if M12 = 1
1
4
3
2
Table 10-2. Divider D2 between PLL1 and PLL2
D20 (bit)
Decimally
D2 (Block Diagram),if M12 = 0
0
0
6
0
1
8
D2 (Block Diagram),if M12 = 1
3
4
Table 10-3. Divider D3 for PLL1
D31 (bit)
D30 (bit)
0
0
0
1
1
0
1
1
Decimally
0
1
2
3
D3 (Block Diagram)
1
2
6
4
10.1
Divider M for Reference Frequency of PLL1
There are several countries like Spain, the Netherlands and Portugal with relatively low modula-
tor frequencies fMod. In case of modulation there will be a big maximum time shift between
pulses coming from fractional divider and pulses coming from reference frequency divider. As a
consequence the phase comparator enters an undesired operation mode. To avoid entering this
operation mode the reference frequency f_Ref1 has to be reduced by a factor M. Simultaneously,
keeping f_Mod constant, the factors of fractional dividers have to be changed as well.
The connection between the additional reference frequency divider M and the factors P_M and Q_M
of fractional divider is given below. The subscript M denotes which value of M refers to the fac-
tors P_M and Q_M of fractional divider. The formulas take into account that the numerator of the
fraction Q_M/223 must not exceed 223.
P_M = P₁ × M + integer (Q × M/223)
Q_M = Q₁ × M - 223 × integer (Q₁ × M/223)
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