LMX2335L National Semiconductor Corporation, LMX2335L Datasheet - Page 13

• Manufacturer Part Number: LMX2335L
• Description: Pllatinum? Low Power Dual Frequency Synthesizer For Rf Personal Communications
• Manufacturer: National Semiconductor Corporation

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
f
B:
A:
f
R:
P:
VCO
OSC
= [(P x B) + A] x f
: Output frequency of external voltage controlled oscillator (VCO)
: Output frequency of the external reference frequency oscillator
Preset divide ratio of binary 11-bit programmable counter (3 to 2047)
Preset divide ratio of binary 7-bit swallow counter
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 ≤ P; A ≤ B)
OSC
o
LD pin. The prescaler and power down modes are selected with bits N19 and N20. The programmable
Note:
/R
Divide ratio: 3 to 2047 (Divide ratios less than 3 are prohibited)
B ≥ A
Divide
Ratio
2047
B
3
4
•
18
N
0
0
1
•
(Continued)
Notes:
17
N
0
0
1
•
Divide
Divide ratio: 0 to 127
B ≥ A
A
Ratio
127
<
A
0
1
•
P
16
N
0
0
1
•
N
7
0
0
1
•
15
N
0
0
1
•
N
6
0
0
1
•
14
13
N
0
0
1
N
•
5
0
0
1
•
N
4
0
0
1
•
13
N
0
0
1
•
N
3
0
0
1
•
12
N
0
0
1
N
•
2
0
0
1
•
o
LD output are shown in Table 2 and Table 3.
N
1
0
1
1
•
11
N
0
0
1
•
10
N
0
1
1
•
N
9
1
0
1
•
01280707
N
8
1
0
1
•
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