lmk03000c National Semiconductor Corporation, lmk03000c Datasheet - Page 16

• Manufacturer Part Number: lmk03000c
• Description: Precision Clock Conditioner With Integrated Vco
• Manufacturer: National Semiconductor Corporation

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2.4 REGISTER R11
This register only has one bit and only needs to be programmed in the case that the phase detector frequency is greater than 20
MHz and digital lock detect is used. Otherwise, it is automatically defaulted to the correct values.
2.4.1 DIV4 -- High Phase Detector Frequencies and Lock Detect
This bit divides the frequency presented to the digital lock detect circuitry by 4. It is necessary to get a reliable output from the
digital lock detect output in the case of a phase detector frequency frequency greater than 20 MHz.
2.5 REGISTER R13
2.5.1 VCO_C3_C4_LF[3:0] -- Value for Internal Loop Filter Capacitors C3 and C4
These bits control the capacitor values for C3 and C4 in the internal loop filter.
2.5.2 VCO_R3_LF[2:0] -- Value for Internal Loop Filter Resistor R3
These bits control the R3 resistor value in the internal loop filter. The recommended setting for VCO_R3_LF[2:0] = 0 for optimum
phase noise and jitter.
DIV4
0
1
VCO_C3_C4_LF[3:0]
VCO_R3_LF[2:0]
12 to 15
5 to 7
10
11
0
1
2
3
4
5
6
7
8
9
0
1
2
3
4
Not divided; Phase Detector Frequency
Divided by 4; Phase Detector Frequency > 20 MHz
Digital Lock Detect Circuitry Mode
16
0 (default)
C3 (pF)
100
100
100
150
150
50
50
50
0
0
0
Loop Filter Capacitors
Low (~600 Ω) (default)
R3 Value (kΩ)
Invalid
Invalid
10
20
30
40
≤
10 (default)
20 MHz (default)
C4 (pF)
110
110
110
160
160
110
60
10
10
60
60