fs6131 AMI Semiconductor, Inc., fs6131 Datasheet - Page 20

• Manufacturer Part Number: fs6131
• Description: Fs6131-01g Programmable Line Lock Clock Generator Ic
• Manufacturer: AMI Semiconductor, Inc.

FS6131-01/FS6131-01g Programmable Line Lock Clock Generator IC
Table 9: Crystal Loop Tuning Bits
Table 10: Crystal Loop Control ROM
6.1 VCXO Coarse Tune
The VCXO may be coarse tuned by a programmable adjustment of the crystal load capacitance via XCT[3:0]. The actual amount of
frequency warping caused by the tuning capacitance will depend on the crystal used. The VCXO tuning capacitance includes an
external 6pF load capacitance (12pF from the XIN pin to ground and 12pF from the XOUT pin to ground). The fine tuning capability of
the VCXO can be enabled by setting the XLVTEN bit to a logic-one, or disabled by setting the bit to a logic-zero.
Name
XLCP[1:0]
(Bits 53-52)
XLROM[2:0]
(Bits 51-49)
XLVTEN
(Bit 61)
XLSWAP
(Bit 54)
XLPDEN
(Bit 55)
XCT[3:0]
(Bits 59-56)
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XLROM
[2]
0
0
0
0
1
1
1
1
Specifications subject to change without notice
XLROM
– Rev. 3.0, Jan. 08
[1]
0
0
1
1
0
0
1
1
Description
Crystal Loop Charge Pump current
Bit 53 = 0
Bit 52 = 0
Bit 53 = 0
Bit 52 = 1
Bit 53 = 1
Bit 52 = 0
Bit 53 = 1
Bit 52 = 1
Crystal Loop Divider ROM select and Crystal Oscillator Power-Down
(see Error! Reference source not found.)
Crystal Loop Voltage fine Tune ENable
Bit = 0
Bit = 1
Crystal Loop SWAP polarity
Bit = 0
Bit = 1
Crystal Loop Power Down Enable
Bit = 0
Bit = 1
Crystal Coarse Tune (see Table 11)
XLROM
[0]
0
1
0
1
0
1
0
1
Crystal oscillator power-down
Current = 1.5µA
Current = 5µA
Current = 8µA
Current = 24µA
Disabled (fine tune is inactive)
Enabled (fine tune is active)
Use with an external VCXO that increases in
frequency in response to an increasing voltage at
the XTUNE pin.
Use with a VCXO that increases in frequency in
response to a decreasing voltage at the XTUNE
pin.
Use this setting for Internal VCXO
Disabled (crystal loop operates)
Enabled
(crystal loop is powered down)
VCXO Divider
3072
3156
2430
2500
4000
3375
1
20
Crystal Frequency (MHz)
24.576
25.248
19.44
20.00
32.00
27.00
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Data Sheet