LMX2335 National Semiconductor, LMX2335 Datasheet - Page 9

• Manufacturer Part Number: LMX2335
• Description: PLLatinum Dual Frequency Synthesizer for RF Personal Communications
• Manufacturer: National Semiconductor

Functional Description
PROGRAMMABLE DIVIDER (N COUNTER)
Each N counter consists of the 7-bit swallow counter (A counter) and the 11-bit programmable counter (B counter). If the Control
Bits are 10 or 11 (10 for RF2 counter and 11 for RF1 counter) data is transferred from the 20-bit shift register into a 7-bit latch
(which sets the Swallow (A) Counter) and an 11-bit latch (which sets the 11-bit programmable (B) Counter), MSB first. Serial data
format is shown below.
7-BIT SWALLOW COUNTER DIVIDE RATIO (A COUNTER)
11-BIT PROGRAMMABLE COUNTER DIVIDE RATIO (B COUNTER)
PULSE SWALLOW FUNCTION
f
PROGRAMMABLE MODES
Several modes of operation can be programmed with bits R16–R20 including the phase detector polarity, charge pump tristate
and the output of the F
modes are shown in Table 1 . Truth table for the programmable modes and F
VCO
Notes: Divide ratio: 3 to 2047 (Divide ratios less than 3 are prohibited)
B
f
B:
A:
f
R:
P:
VCO
OSC
A
Divide
= [(P x B) + A] x f
Ratio
2047
:
:
B
3
4
•
Output frequency of external voltage controlled oscillator (VCO)
Preset divide ratio of binary 11-bit programmable counter (3 to 2047)
Preset divide ratio of binary 7-bit swallow counter
Output frequency of the external reference frequency oscillator
Preset divide ratio of binary 15-bit programmable reference counter (3 to 32767)
Preset modulus of dual moduIus prescaler (P = 64 or 128)
(0
A
18
N
0
0
1
•
P; A
o
OSC
LD pin. The prescaler and power down modes are selected with bits N19 and N20. The programmable
/R
B)
17
N
0
0
1
•
(Continued)
16
N
0
0
1
•
Notes: Divide ratio: 0 to 127
B
A
Divide
Ratio
<
127
A
A
0
1
P
•
15
N
0
0
1
•
N
7
0
0
1
•
N
6
0
0
1
•
14
N
0
0
1
•
9
N
5
0
0
1
•
N
4
0
0
1
•
13
N
0
0
1
•
N
3
0
0
1
•
N
2
0
0
1
•
o
LD output are shown in Tables 2, 3 .
12
N
1
0
1
1
N
•
0
0
1
•
11
N
0
0
1
•
DS012332-5
10
N
0
1
1
•
N
9
1
0
1
•
www.national.com
N
8
1
0
1
•