lmx2515 National Semiconductor Corporation, lmx2515 Datasheet - Page 14

• Manufacturer Part Number: lmx2515
• Description: Pllatinum? Frequency Synthesizer System With Integrated Vco
• Manufacturer: National Semiconductor Corporation

www.national.com
Programming Description
Pulse Swallow Function
f
f
f
RF_B: Preset divide ratio of binary 4-bit programmable counter (2 ≤ RF_B ≤ 15)
RF_A: Preset divide ratio of binary 3-bit swallow counter (0 ≤ RF_A ≤ 7 for LMX2515LQ1321 and 0 ≤ RF_A ≤ 3 for
LMX2515LQ0701)
RF_FN: Preset numerator of binary 10-bit modulus counter (0 ≤ RF_FN
FD: Preset denominator for modulus counter (FD = f
f
R: Internal reference oscillator frequency divider
The value of the denominator (FD) is depended on the channel spacing and reference oscillator frequency. Table 6 summarizes
the denominator values based on the settings of the Rx/Tx, RF_SEL, and OSC_FREQ [1:0] bits.
VCO
VCO
VCO
OSC
LMX2515LQ0701
LMX2515LQ1321
Part Number
: Output frequency of voltage controlled oscillator (VCO)
: Reference oscillator frequency
= {8 x RF_B + RF_A + (RF_FN / FD)} x f
= {4 x RF_B + RF_A + (RF_FN / FD)} x f
OSC_FREQ [1:0]
00
01
10
11
RF_SEL
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Rx/Tx
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
OSC_FREQ [1:0]
(Continued)
OSC
OSC
Reference Oscillator Frequency (MHz)
TABLE 6. Demonimator Values
/ R where (RF_A
/ R where (RF_A
OSC
00
01
10
11
00
01
10
11
00
01
10
11
00
01
10
11
/(R x f
14
CH
12.6
14.4
25.2
26.0
) where f
Reference Oscillator
Frequency (MHz)
<
<
RF_B) for LMX2515LQ1321
RF_B) for LMX2515LQ0701
<
CH
FD)
12.6
14.4
25.2
26.0
12.6
14.4
25.2
26.0
12.6
14.4
25.2
26.0
12.6
14.4
25.2
26.0
is the channel spacing)
R
1
1
2
2
1
1
2
2
1
1
2
2
1
1
2
2
f
CH
22.22
22.22
22.22
22.22
25.0
25.0
25.0
25.0
20.0
20.0
20.0
20.0
25.0
25.0
25.0
25.0
(kHz)
R Divider
Denominator
1
1
2
2
(FD)
504
576
504
520
630
720
630
650
504
576
504
520
567
648
567
585