User Guide

NSD-5
3. System Module PAMS Technical Documentation
Page 52 Nokia Corporation Issue 1 05/02
f
OSC
: Output frequency of the external reference frequency oscillator
R: Preset divide ratio of binary 15-bit programmable reference counter (3 to 32767)
P: Preset modulus of dual modulus prescaler (for IF: P=8 or 16; for RF: P = 32 or 64)
N = (Px B)+A
Programmable Modes
Several modes of operation can be programmed with bits R16-R20, including the phase
detector polarity, charge pump TRI-STATE, and the output of the Fo LD pin. The prescaler
and powerdown modes are selected with bits N19 and N20. The programmable modes
are shown below. Truth table for the programmable modes and Fo LD output are shown
below.
Depending upon VCO characteristics, R16 bit should be set accordingly (see the following
figure):
When VCO characteristics are positive like (1), R16 should be set HIGH.
When VCO characteristics are negative like (2), R16 should be set LOW.
We used positive polarity VCO in our PLL circuits.
C1 C2 R16 R17 R18 R19 R20
0 0 IF phase
detector
polarity
IF I
CPo
IF D
o
TRI-STATE
IF LD IF F
o
01RF phase
detector
polarity
RF I
CPo
RF D
o
TRI-STATE
RF LD RF F
o
C1 C2 N19 N20
1 0 IF prescaler Pwdn IF
1 1 RF prescaler Pwdn RF
Phase Detector Polarity Do TRI-STATE I
CPo
IF
Prescaler
RF
Prescaler
Pwdn
0 Negative Normal
Operation
LOW 9/0 32/33 Pwdn Up
1 Positive TRI-STATE HIGH 16/17 64.65 Pwdn Dn