User Manual

PROGRAMMING

3-3

June 1997

Part No. 001-3412-002

3.2.4 B-WORD CALCULATION (24-BITS)

The B-Word programs the Fractional-N charge

pump current setting factor, the Binary acceleration

factors (CL/CK) and prescaler modulus.

The value of CN should be interpolated for fre-

quencies between the band edges. The recommended

value range of CN provides the fractional spurious

rejection required to meet adjacent channel specifica-

tions. The CN values could be changed on a channel-

by-channel basis for ultimate rejection of the Frac-

tional-N spurious responses close to the carrier fre-

quency. The DM-3412 has an adjustment (R823) for

fractional compensation current. The factory preset

value of R823 allows CN to be set to the following

ranges:

Lowest Tx Frequency 86

Highest Tx Frequency 90

Lowest Rx Frequency 96

Highest Rx Frequency 100

CN = (8-bit) (Frequency dependent)

(86-90 Tx) (96-100 Rx)

CK = 0000 Binary acceleration factor for integral

charge pump

CL = 00 Binary acceleration factor for

proportional charge pump

PR = 01 Select modulus 2 prescaler (64/65)

B-Word = 0x80 (8-bit CN) 0x02

Figure 3-3 B-WORD

321 141312111098765 2019181715 16 24232221

1 0 100000000000

ADDRESS

BITS

0/1 0/1 0/1 0/1 0/1 0/1 0/1 0/1 0 0

NOT USED

(ALWAYS 0000)

(CHANNEL DEPENDENT)

(CHARGE PUMP CURRENT SETTING)

CN CL

BINARY ACCELERATION

FACTOR (ALWAYS 000000)

PR (PRESCALER TYPE) (01=DUAL MODULUS)