Texas Instruments LMK04131 Clock Jitter Cleaner with Cascade PLL LMK04131EVAL/NOPB LMK04131EVAL/NOPB 데이터 시트
제품 코드
LMK04131EVAL/NOPB
L M K 0 4 1 X X - R E V 3 E V A L U A T I O N B O A R D O P E R A T I N G I N S T R U C T I O N S
SNLU099
4
PLL Loop Filters and Loop Parameters
The loop filters on the LMK041xx evaluation board are setup using the approach above. The
loop filter for PLL1 has been configured for a narrow loop bandwidth (< 100 Hz), while the loop
filter of PLL2 has been configured for a wide loop bandwidth (> 100 kHz). The specific loop
bandwidth values depend on the phase noise performance of the oscillator mounted on the board.
The following tables contain the parameters for PLL1 and PLL2 for each oscillator option.
National‟s Clock Design Tool can be used to optimize PLL phase noise/jitter for given
specifications. See:
loop filter for PLL1 has been configured for a narrow loop bandwidth (< 100 Hz), while the loop
filter of PLL2 has been configured for a wide loop bandwidth (> 100 kHz). The specific loop
bandwidth values depend on the phase noise performance of the oscillator mounted on the board.
The following tables contain the parameters for PLL1 and PLL2 for each oscillator option.
National‟s Clock Design Tool can be used to optimize PLL phase noise/jitter for given
specifications. See:
http://www.ti.com/tool/clockdesigntool
PLL 1 Loop Filter
Table 1. PLL1 Loop Filter Parameters for Crystek 122.88 MHz VCXO and 12.288 MHz Vectron Crystal
Phase Margin
50º
Kφ (Charge Pump)
100 uA
Loop Bandwidth
12 Hz
Phase Detector Freq
1.024 MHz
VCO Gain
2.5 kHz/Volt
Reference Clock
Frequency
122.88 MHz
Output Frequency
122.88 MHz (To PLL 2)
Loop Filter Components
C1 = 100 nF
C2 = 680 nF
R2 = 39 kΩ
PLL2 Loop Filter
122.88 MHz VCXO (Reference Input)
LMK041x0B
LMK041x1B
LMK041x2B
LMK041x3B
Units
C1
Open
C2
12
nF
C3
0
nF
C4
0.01
nF
R2
1.8
kΩ
R3
0.6
kΩ
R4
0.2
kΩ
Charge Pump
Current, K
3.2
mA
Phase Detector
Frequency
61.44
MHz
Frequency
1228.8
1474.56
1720.32
1966.08
MHz
Kvco
8
9
13
19
MHz/V
N
20
24
28
32
Phase Margin
85.5
85.5
85.0
84.0
degrees
Loop Bandwidth
366
343
424
542
kHz
Note: PLL Loop Bandwidth is a function of K , Kvco, N as well as loop components. Changing
K and N will change the loop bandwidth.