Datasheet

MAX2831/MAX2832
2.4GHz to 2.5GHz 802.11g/b
RF Transceivers with Integrated PA
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Calculating Integer and Fractional Divider Ratios
The desired integer and fractional divider ratios can be
calculated by dividing the RF frequency (f
RF
) by f
COMP
.
For nominal 802.11g/b operation, a 40MHz reference
oscillator is divided by 2 to generate a 20MHz compari-
son frequency (f
COMP
). The following method can be
used when calculating divider ratios supporting various
reference and comparison frequencies:
LO Frequency Divider = f
RF
/ f
COMP
= 2437MHz /
20MHz = 121.85
Integer Divider = 121 (d) = 0111 1001 (binary)
Fractional Divider = 0.85 x (2
20
- 1) = 891289 (decimal)
= 1101 1001 1001 1001 1001
See Table 13 for integer and fractional divider ratios for
802.11g/b systems using a 20MHz comparison frequency.
Table 11. Integer Divider Register (A3:A0 = 0011)
BIT RECOMMENDED DESCRIPTION
D13:D8 00000 6 LSBs of 20-Bit Fractional Portion of Main Divider
D7:D0 01111001 8-Bit Integer Portion of Main Divider. Programmable from 64 to 255.
Table 12. Fractional Divider Register (A3:A0 = 0100)
BIT RECOMMENDED DESCRIPTION
D13:D0 11011001100110 14 MSBs of 20-Bit Fractional Portion of Main Divider
Table 13. IEEE 802.11g/b Divider-Ratio Programming Words
INTEGER DIVIDER FRACTIONAL DIVIDER
f
RF
(MHz)
(f
RF
/ f
COMP
)
A3:A0 = 0011, D7:D0 A3:A0 = 0100, D13:D0 A3:A0 = 0011, D13:D8
2412 120.6 0111 1000b 2666h 1Ah
2417 120.85 0111 1000b 3666h 1Ah
2422 121.1 0111 1001b 0666h 1Ah
2427 121.35 0111 1001b 1666h 1Ah
2432 121.6 0111 1001b 2666h 1Ah
2437 121.85 0111 1001b 3666h 1Ah
2442 122.1 0111 1010b 0666h 1Ah
2447 122.35 0111 1010b 1666h 1Ah
2452 122.6 0111 1010b 2666h 1Ah
2457 122.85 0111 1010b 3666h 1Ah
2462 123.1 0111 1011b 0666h 1Ah
2467 123.35 0111 1011b 1666h 1Ah
2472 123.6 0111 1011b 2666h 1Ah
2484 124.2 0111 1100b 0CCCh 33h