lmx2522lq1635 National Semiconductor Corporation, lmx2522lq1635 Datasheet - Page 11

• Manufacturer Part Number: lmx2522lq1635
• Description: Pllatinum Frequency Synthesizer System With Integrated Vcos
• Manufacturer: National Semiconductor Corporation

Programming Description
R0 REGISTER
The R0 register address bits (R0 [1:0]) are “00”.
The SPI_DEF bit selects between using the default IF counter values and user programmable values. The use of the default
counter values requires that only words R0 to R3 (registers R3, loaded first, to R0, loaded last) be sent after initial power up.
The RF_LD bit activates the lock detect output of the LD pin (pin 19). The lock detect mode shows the lock status of the RF PLL.
The waveform of the lock detect mode is shown in Figure 1, in the Functional Description section on LOCK DETECT.
The SPUR_CRL bit is set to 1 only in the GPS mode with the LMX2532LQ1065 when a 19.68 MHz reference oscillator is used.
The RF N counter consists of the 4-bit programmable counter (RF_B counter), the 3-bit swallow counter (RF_A counter) and the
11-bit delta sigma modulator (RF_FN counter). The equations for calculating the counter values are presented below.
R0
(Default)
Name
SPI_DEF
RF_SEL
RF_LD
SPUR_CRL
RF_B [3:0]
RF_A [2:0]
RF_FN [10:0]
MSB
23
SPI_
DEF
Device Type
LMX2522
LMX2532
22
RF_
SEL
21
RF_
LD
20
SP
UR_
CRL
19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1
RF_B
[3:0]
Functions
Default Register Selection
0 = OFF (Use values set in R0 to R6)
1 = ON (Use default values set in R0 to R3)
RF Select Configuration
See Table 8. RF_SEL Configuration below
RF Lock Detect
0 = Hard zero (GND)
1 = Lock detect
Spur Control
1 = LMX2532LQ1065 in GPS mode with 19.68 MHz reference oscillator only
0 = All other options
RF_B Counter
4-bit programmable counter
2 ≤ RF_B ≤ 15
RF_A Counter
3-bit swallow counter
0 ≤ RF_A ≤ 7 for LMX2522
0 ≤ RF_A ≤ 5 for LMX2532
RF Fractional Numerator Counter
11-bit programmable counter
0 ≤ RF_FN
0 ≤ RF_FN
(Continued)
TABLE 8. RF_SEL Configuration
SHIFT REGISTER BIT LOCATION
<
<
1920 for f
1968 for f
R0 REGISTER
RF_SEL = 0
GPS
K-Cellular
Data Field
RF_A
[2:0]
11
OSC
OSC
= 19.20 MHz
= 19.68 MHz
RF_FN
[10:0]
RF_SEL = 1
K-PCS
GPS
www.national.com
0
Address
Field
LSB
0
0