LMX2331A National Semiconductor, LMX2331A Datasheet - Page 11

• Manufacturer Part Number: LMX2331A
• Description: PLLatinum Dual 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
Bits are 10 or 11 (10 for IF counter and 11 for RF counter) data is transferred from the 22-bit shift register into a 4-bit or 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. For the IF N counter bits 5, 6, and 7 are don’t care bits. The RF N counter does not have don’t care
bits.
7-BIT SWALLOW COUNTER DIVIDE RATIO (A COUNTER)
RF
11-BIT PROGRAMMABLE COUNTER DIVIDE RATIO (B COUNTER)
Note: Divide ratio: 3 to 2047 (Divide ratios less than 3 are prohibited)
B
PULSE SWALLOW FUNCTION
f
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 F
grammable modes are shown in Table 1 . Truth table for the programmable modes and F
Table 3 .
VCO
f
B:
A:
f
R:
P:
VCO
OSC
A
Divide
Ratio
2047
= [(P x B) + A] x f
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 (for IF ; P = 8 or 16;
for RF ; LMX2330A: P = 32 or 64
Note: Divide ratio: 0 to 127
B
Divide
(0
Ratio
127
A
A
0
1
•
A
18
N
0
0
1
•
127 {RF}, 0
N
7
0
0
1
•
OSC
N
6
0
0
1
•
/R
N
17
5
0
0
1
•
N
0
0
1
•
N
4
0
0
1
•
o
A
LD pin. The prescaler and powerdown modes are selected with bits N19 and N20. The pro-
N
3
0
0
1
•
(Continued)
15 {IF}, A
16
N
0
0
1
•
N
2
0
0
1
•
N
1
0
1
1
•
LMX2331A/32A: P = 64 or 128)
15
N
0
0
1
•
B)
14
N
0
0
1
•
11
IF
13
N
0
0
1
•
X = DON’T CARE condition
Divide
Ratio
12
15
N
0
0
1
A
•
0
1
•
N
X
X
X
7
•
o
LD output are shown in Table 2 and
11
N
0
0
1
•
N
X
X
X
6
•
DS012331-15
N
X
X
X
5
•
N
4
0
0
1
•
10
N
0
1
1
•
N
3
0
0
1
•
N
2
0
0
1
•
N
N
9
1
0
1
1
0
1
1
•
•
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N
8
1
0
1
•