LMX2306 Datasheet, PDF (8/19 Pages) National Semiconductor (TI) – PLLatinum™ Low Power Frequency Synthesizer for RF Personal Communications

1.0 Functional Description (Continued)
1.2 PROGRAMMABLE DIVIDER (N COUNTER)
The N counter consists of the 5-bit swallow counter (A counter) and the 13-bit programmable counter (B counter). If the Control
Bits are [C₁, C₂] = [1,0], data is transferred from the 21-bit shift register into a 5-bit latch (which sets the Swallow (A) Counter),
a 13-bit latch (which sets the 13-bit programmable (B) Counter), and the GO bit (See Section 1.3.4 FastLock MODES section)
MSB first. For the LMX2306 the maximum N value is 65535 and the minimum N value is 56. For the LMX2316/26, the maximum
N value is 262143 and the minimum N value is 992. Serial data format is shown below.
Note: Data is shifted in MSB first.
1.2.1 5-BIT SWALLOW COUNTER DIVIDE RATIO (A COUNTER)
LMX2316/26
LMX2306
DS100127-6
Divide
N
N
N
N
N
Ratio
5
4
3
2
1
0
0
0
0
0
0
1
0
0
0
0
1
•
•
•
•
•
•
31
1
1
1
1
1
Note: Divide ratio: 0 to 31
B≥A
Divide
N
N
N
N
N
Ratio
5
4
3
2
1
0
X
X
0
0
0
1
X
X
0
0
1
•
•
•
•
•
•
7
X
X
1
1
1
Note: Divide ratio: 0 to 7
B≥A
X denotes a Don’t Care condition
1.2.2 13-BIT PROGRAMMABLE COUNTER DIVIDE RATIO (B COUNTER)
Divide
N
N
N
N
N
N
N
N
N
N
N
N
N
Ratio
18
17
16
15
14
13
12
11
10
9
8
7
6
3
0
0
0
0
0
0
0
0
0
0
0
1
1
4
0
0
0
0
0
0
0
0
0
0
1
0
0
•
•
•
•
•
•
•
•
•
•
•
•
•
•
8191
1
1
1
1
1
1
1
1
1
1
1
1
1
Divide ratio: 3 to 8191 (Divide ratios less than 3 are prohibited) B≥A
1.2.3 PULSE SWALLOW FUNCTION
fvco = [(P x B) + A] x fosc/R
f_vco: Output frequency of external voltage controlled oscillator (VCO)
B: Preset divide ratio of binary 13-bit programmable counter (3 to 8191)
A: Preset divide ratio of binary 5-bit swallow counter (0 ≤ A ≤ 31; A ≤ B for LMX2316/26)
or (0 ≤ A ≤ 7, A ≤ B for LMX2306)
f_osc: Output frequency of the external reference frequency oscillator
R: Preset divide ratio of binary 14-bit programmable reference counter (3 to 16383)
P: Preset modulus of dual modulus prescaler
for the LMX2306; P = 8 for the LMX2316/26; P = 32
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