LMX1501 National Semiconductor, LMX1501 Datasheet - Page 10

• Manufacturer Part Number: LMX1501
• Description: PLLatinumTM 1.1 GHz Frequency Synthesizer for RF Personal Communications
• Manufacturer: National Semiconductor

Functional Description
The simplified block diagram below shows the 19-bit data register the 14-bit R Counter and the S Latch and the 18-bit
N Counter (intermediate latches are not shown) The data stream is clocked (on the rising edge) into the DATA input MSB first
If the Control Bit (last bit input) is HIGH the DATA is transferred into the R Counter (programmable reference divider) and the
S Latch (prescaler select 64 65 or 128 129) If the Control Bit (LSB) is LOW the DATA is transferred into the N Counter
(programmable divider)
PROGRAMMABLE REFERENCE DIVIDER (R COUNTER) AND PRESCALER SELECT (S LATCH)
If the Control Bit (last bit shifted into the Data Register) is HIGH data is transferred from the 19-bit shift register into a 14-bit
latch (which sets the 14-bit R Counter) and the 1-bit S Latch (S15 which sets the prescaler 64 65 or 128 129) Serial data
format is shown below
14-BIT PROGRAMMABLE REFERENCE DIVIDER RATIO
(R COUNTER)
Notes Divide ratios less than 3 are prohibited
Divide
16383
Ratio
R
3
4
Divide ratio 3 to 16383
S1 to S14 These bits select the divide ratio of the programmable
reference divider
C Control bit (set to HIGH level to load R counter and S Latch)
Data is shifted in MSB first
14
S
0
0
1
13
S
0
0
1
12
S
0
0
1
11
S
0
0
1
10
S
0
0
1
S
9
0 0 0 0 0 0 0 1 1
0 0 0 0 0 0 1 0 0
1 1 1 1 1 1 1 1 1
S
8
S
7
S
6
S
5
S
4
10
S
3
S
2
S
1
1-BIT PRESCALER SELECT
(S LATCH)
Prescaler
128 129
Select
64 65
P
TL W 12340 – 20
15
S
0
1
TL W 12340 – 19