LMX2305 National Semiconductor, LMX2305 Datasheet - Page 7

• Manufacturer Part Number: LMX2305
• Description: PLLatinumTM 550 MHz Frequency Synthesizer for RF Personal Communications
• Manufacturer: National Semiconductor

Functional Description
PROGRAMMABLE DIVIDER (N COUNTER)
The N counter consists of the 7-bit swallow counter (A counter) and the 11-bit programmable counter (B counter) If the Control
Bit (last bit shifted into the Data Register) is LOW data is transferred from the 19-bit shift register into a 7-bit latch which sets
the 7-bit Swallow (A) Counter and an 11-bit latch which sets the 11-bit programmable (B) Counter Serial data format is shown
below
Note S8 to S18 Programmable counter divide ratio control bits (3 to 2047)
7-BIT SWALLOW COUNTER DIVIDE RATIO
(A COUNTER)
Note Divide ratio 0 to 127
Divide
Ratio
127
A
0
1
B
t
A
N
7
0
0
1
N
6
0
0
1
N
5
0
0
1
N
4
0
0
1
N
3
0
0
1
N
2
0
0
1
N
1
0
1
1
(Continued)
7
11-BIT PROGRAMMABLE COUNTER DIVIDE RATIO
(B COUNTER)
Note Divide ratio 3 to 2047 (Divide ratios less than 3 are prohibited)
PULSE SWALLOW FUNCTION
f
f
B
A
f
R
P
VCO
VCO
OSC
Divide
Ratio
2047
B
3
4
e
B
Output frequency of external voltage controlled oscil-
lator (VCO)
Preset divide ratio of binary 11-bit programmable
counter (3 to 2047)
Preset divide ratio of binary 7-bit swallow counter
(0
Output frequency of the external reference frequency
oscillator
Preset divide ratio of binary 14-bit programmable ref-
erence counter (3 to 16383)
Preset modulus of dual modulus prescaler (64 or 128)
t
(P
s
A
18
N
0
0
1
c
A
B)
s
17
N
0
0
1
127 A
a
16
N
0
0
A
1
c
15
s
N
0
0
1
f
OSC
B)
14
N
0
0
1
R
13
N
0
0
1
12
N
0
0
1
http
11
N
TL W 12459 – 15
0
0
1
www national com
10
N
0
1
1
N
9
1
0
1
N
8
1
0
1