Texas Instruments LMK04906 Series User manual

LMK04906 Evaluation Board
User's Guide
January 2012
Literature Number SNAU126A
Revised – December 2013

2SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
LMK04906 Family
Low-Noise Clock Jitter Cleaner with Dual Loop PLLs
Evaluation Board Instructions

Revised - December 2013 LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs SNAU126A 3
Copyright © 2013, Texas Instruments Incorporated
Table of Contents
TABLE OF CONTENTS ..............................................................................................................................................................3
GENERAL DESCRIPTION ..........................................................................................................................................................5
Evaluation Board Kit Contents..................................................................................................................5
Available LMK04906 Evaluation Boards .................................................................................................5
Available LMK04906 Family Devices......................................................................................................5
QUICK START ..........................................................................................................................................................................6
Default CodeLoader Modes for Evaluation Boards...................................................................................7
EXAMPLE: USING CODELOADER TO PROGRAM THE LMK04906B ............................................................................................8
1. Start CodeLoader 4 Application ............................................................................................................8
2. Select Device .........................................................................................................................................8
3. Program/Load Device............................................................................................................................9
4. Restoring a Default Mode......................................................................................................................9
5. Visual Confirmation of Frequency Lock.............................................................................................10
6. Enable Clock Outputs..........................................................................................................................10
PLL LOOP FILTERS AND LOOP PARAMETERS .........................................................................................................................12
PLL 1 Loop Filter ....................................................................................................................................12
25 MHz VCXO PLL............................................................................................................................12
PLL2 Loop Filter .....................................................................................................................................13
EVALUATION BOARD INPUTS AND OUTPUTS........................................................................................................................14
RECOMMENDED TEST EQUIPMENT ......................................................................................................................................21
APPENDIX A: CODELOADER USAGE.......................................................................................................................................22
Port Setup Tab..........................................................................................................................................22
Clock Outputs Tab...................................................................................................................................23
PLL1 Tab .................................................................................................................................................26
Setting the PLL1 VCO Frequency and PLL2 Reference Frequency...................................................27
PLL2 Tab .................................................................................................................................................28
Bits/Pins Tab............................................................................................................................................29
Registers Tab ...........................................................................................................................................34
APPENDIX B: TYPICAL PHASE NOISE PERFORMANCE PLOTS..................................................................................................35
PLL1 ........................................................................................................................................................35
25 MHz VCXO Phase Noise ...............................................................................................................35
Clock Output Measurement Technique...............................................................................................36
Clock Outputs (CLKout)..........................................................................................................................37

4SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
LMK04906B CLKout Phase Noise.....................................................................................................37
APPENDIX C: SCHEMATICS....................................................................................................................................................38
Power Supplies.........................................................................................................................................38
LMK04906B Device with Loop Filter and Crystal Circuits ...................................................................39
Reference Inputs (CLKin0, CLKin1 & CLKin2), External VCXO (OSCin) & VCO Circuits...............40
Clock Outputs (OSCout0, CLKout0 to CLKout5) ..................................................................................41
uWire Header, Logic I/O Ports and Status LEDs....................................................................................42
APPENDIX D: BILL OF MATERIALS .........................................................................................................................................43
APPENDIX E: PCB LAYERS STACKUP .....................................................................................................................................47
APPENDIX F: PCB LAYOUT.....................................................................................................................................................48
Layer #1 – Top.........................................................................................................................................48
Layer #2 – RF Ground Plane (Inverted)..................................................................................................49
Layer #3 – Vcc Planes .............................................................................................................................50
Layer #4 – Ground Plane (Inverted)........................................................................................................51
Layer # 5 – Vcc Planes 2 .........................................................................................................................52
Layer #6 – Bottom...................................................................................................................................53
Layers #1 and 6 – Top and Bottom (Composite).....................................................................................54
APPENDIX G: PROPERLY CONFIGURING LPT PORT ................................................................................................................55
LPT Driver Loading.................................................................................................................................55
Correct LPT Port/Address........................................................................................................................55
Correct LPT Mode...................................................................................................................................56
Legacy Board Port Setup.........................................................................................................................56
APPENDIX H: TROUBLESHOOTING INFORMATION................................................................................................................57
1) Confirm Communications................................................................................................................57
2) Confirm PLL1 operation/locking.....................................................................................................57
3) Confirm PLL2 operation/locking.....................................................................................................58
APPENDIX I: EVM SOFTWARE AND COMMUNICATION .........................................................................................................59
OPTION 1................................................................................................................................................59
OPTION 2................................................................................................................................................59

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Copyright © 2013, Texas Instruments Incorporated
General Description
The LMK04906 Evaluation Board simplifies evaluation of the LMK04906B Low-Noise Clock
Jitter Cleaner with Dual Loop PLLs. Texas Instrument’s CodeLoader software can be used to
program the internal registers of the LMK04906B device through the USB2ANY-uWIRE
interface. The CodeLoader software will run on a Windows 2000/XP or Windows 7 PC and can
be downloaded from http://www.ti.com/tool/codeloader.
Evaluation Board Kit Contents
The evaluation board kit includes:
•(1) LMK04906 Evaluation Board from Table 1
•(1) CodeLoader and USB2ANY-uWIRE Interface uWire header on EVM
Available LMK04906 Evaluation Boards
The LMK04906 Evaluation Board supports any of the four devices offered in the LMK04906
Family. All evaluation boards use the same PCB layout and bill-of-materials, except for the
corresponding LMK04906B device affixed to the board. A commercial-quality VCXO is also
mounted to the board to provide a known reference point for evaluating device performance and
functionality.
Table 1: Available Evaluation Board Configurations
Evaluation Board ID
Device
PLL1 VCXO
LMK04906BEVAL LMK04906B
25 MHz Epson VCXO
Model VG-4231CA 25.0000M-FGRC3
Available LMK04906 Family Devices
Table 2: LMK04906B Devices
Device Reference
Inputs
Buffered/
Divided
OSCin
Outputs
Programmable
LVDS/LVPECL/
LVCMOS
Outputs
VCO Frequency
LMK04906B
3
1
6
2370 to 2600 MHz

6SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
Quick Start
Full evaluation board instructions are downloadable from the LMK04906B device product folder
at www.ti.com/product/LMK04906.
1. Connect a power supply voltage of 5 V to the Vcc SMA connector. The onboard LP3878-
ADJ LDO regulator will output a low-noise 3.3 V supply to operate the device.
2. Connect a reference clock from a signal source to the CLKin1 SMA port. Use 125 MHz
for default. The reference frequency depends on the device programming.
3. Connect the uWire header to a PC USB port using the USB2ANY-uWIRE interface.
4. Program the device with a default mode using CodeLoader. Ctrl+L must be pressed at
least once to load all registers. Alternatively click menu “Keyboard Controls” “Load
Device”. CodeLoader can be downloaded from www.ti.com/tool/codeloader.
5. Measurements may be made on an active output clock port via its SMA connector.
Figure 1: Quick Start Diagram
125 MHz
(Default)

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Copyright © 2013, Texas Instruments Incorporated
Default CodeLoader Modes for Evaluation Boards
CodeLoader saves the state of the selected LMK04906B device when exiting the software. To
ensure a common starting point, the following modes listed in Table 3 may be restored by
clicking “Mode” and selecting the appropriate device configuration, as shown in Figure 2 in the
case of the LMK04906B device. Similar default modes are available for each LMK04906B
device in CodeLoader. Choose a mode with CLKin0 or CLKin2 for differential clock signal or
CLKin1 for a single ended signal.
Figure 2: Selecting a Default Mode for the LMK04906 Device
After restoring a default mode, press Ctrl+L to program the device. The default modes also
disable certain outputs, so make sure to enable the output under test to make measurements.
Table 3: Default CodeLoader Modes for LMK04906
Default CodeLoader Mode Device Mode
CLKin
Frequency
OSCin
Frequency
122.88 MHz CLKin1, 122.88 MHz
VCXO
Dual PLL, Internal VCO
122.88
MHz
122.88
MHz
125 MHz CLKin1, 25 MHz VCXO
Dual PLL, Internal VCO
125 MHz
25 MHz
The next section outlines step-by-step procedures for using the evaluation board with the
LMK04906B. For boards with another part number, make sure to select the corresponding part
number under the “Device” menu.

8SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
Example: Using CodeLoader to Program the LMK04906B
The purpose of this section is to walk the user through using CodeLoader 4 to make some
measurements with the LMK04906B device as an example. For more information on
CodeLoader refer to Appendix A: CodeLoader Usage or the CodeLoader 4 instructions located
at http://www.ti.com/tool/codeloader.
Before proceeding, be sure to follow the Quick Start section above to ensure proper
connections.
1. Start CodeLoader 4 Application
Click “Start” “Programs” “CodeLoader 4” “CodeLoader 4”
The CodeLoader 4 program is installed by default to the CodeLoader 4 application group.
2. Select Device
Click “Select Device” “Clock Conditioners”
“LMK04906B”
Once started CodeLoader 4 will load the last
used device. To load a new device, click
“Select Device” from the menu bar. Then,
select the subgroup and finally device to
load. In this example, the LMK04906B is
chosen. Selecting the device does cause
the device to be programmed.
Figure 3 – Selecting the LMK04906B device

Revised - December 2013 LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs SNAU126A 9
Copyright © 2013, Texas Instruments Incorporated
3. Program/Load Device
Assuming the Port Setup settings are
correct, press the “Ctrl+L” shortcut or click
“Keyboard Controls” “Load Device” from
the menu to program the device to the
current state of the newly loaded
LMK04906 file.
Once the device has been initially loaded,
CodeLoader will automatically program
changed registers so it is not necessary to re-load the device upon subsequent changes in the
device configuration. It is possible to disable this functionality by ensuring there is no
checkmark by the “Options” “AutoReload with Changes.”
Because a default mode will be restored in the next step, this step is not really needed but is
included to emphasize the importance of pressing “Ctrl+L” to load the device at least once after
starting CodeLoader, restoring a mode, or restoring a saved setup using the File menu.
See Appendix A: CodeLoader Usage or the CodeLoader 4 instructions located at
http://www.ti.com/tool/codeloader for more information on Port Setup. Appendix H:
Troubleshooting Information contains information on troubleshooting communications.
4. Restoring a Default Mode
Click “Mode” “125 MHz CLKin1, 25 MHz VCXO”; then press Ctrl+L.
Figure 5: Setting the Default mode for LMK04906
For the purpose of this walkthrough, a default mode will be loaded to ensure a common starting
point. This is important because when CodeLoader is closed, it remembers the last settings
used for a particular device. Again, remember to press Ctrl+L as the first step after loading a
default mode.
Figure 4 – Loading the Device

10 SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
5. Visual Confirmation of Frequency Lock
After a default mode is restored and loaded, LED D5 should illuminate when PLL1 and PLL2 are
locked to the reference clock applied to CLKin1. This assumes LD_MUX = PLL1/2 DLD and
LD_TYPE = Active High, which are the default settings.
6. Enable Clock Outputs
While the LMK04906B offers programmable clock output buffer formats, the evaluation board is shipped
with preconfigured output terminations to match the default buffer type for each output. Refer to the
CLKout port description in the Evaluation Board Inputs and Outputs section.
To measure phase noise at one of the clock outputs, for example, CLKout0:
1. Click on the Clock Outputs tab,
2. Uncheck “Powerdown” in the Digital Delay box to enable the channel,
3. Set the following settings as needed:
a. Digital Delay value
b. Clock Divider value
c. Analog Delay select and Analog Delay value (if not “Bypassed”)
d. Clock Output type.
4. Depending on the configured output type, the clock output SMAs can be interfaced to a test
instrument with a single-ended 50-ohm input as follows.
a. For LVDS:
i. A balun (like ADT2-1T) is recommended for differential-to-single-ended
conversion.
b. For LVPECL:
i. A balun can be used, or
ii. One side of the LVPECL signal can be terminated with a 50-ohm load and the
other side can be run single-ended to the instrument.
c. For LVCMOS:
i. There are two single-ended outputs, CLKoutX
and CLKoutX*, and each output can be set to
Normal, Inverted, or Off. There are nine (9)
combinations of LVCMOS modes in the Clock
Output list.
ii. One side of the LVCMOS signal can be
terminated with a 50-ohm load and the other
side can be run single-ended to the
instrument.
iii. A balun may also be used. Ensure CLKoutX
and CLKoutX* states are complementary to
each other. That is, Norm/Inv or Inv/Norm.
Figure 7: Setting LVCMOS modes
Figure 6: Setting Digital Delay, Clock Divider, Analog Delay, and Output Format for CLKout0

Revised - December 2013 LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs SNAU126A 11
Copyright © 2013, Texas Instruments Incorporated
5. The phase noise may be measured with a spectrum analyzer or signal source analyzer.
See Appendix B: Typical Phase Noise Performance Plots for phase noise plots of the clock
outputs.
National’s Clock Design Tool can be used to calculate divider values to achieve desired clock
output frequencies. See: http://www.ti.com/tool/clockdesigntool.

12 SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
PLL Loop Filters and Loop Parameters
In jitter cleaning applications that use a cascaded or dual PLL architecture, the first PLL’s
purpose is to substitute the phase noise of a low-noise oscillator (VCXO or crystal resonator) for
the phase noise of a “dirty” reference clock. The first PLL is typically configured with a narrow
loop bandwidth in order to minimize the impact of the reference clock phase noise. The
reference clock consequently serves only as a frequency reference rather than a phase
reference.
The loop filters on the LMK04906 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: http://www.ti.com/tool/clockdesigntool.
PLL 1 Loop Filter
Table 4: PLL1 Loop Filter Parameters for Epson 25 MHz VCXO
25 MHz VCXO PLL
Phase Margin 49˚ Kφ (Charge Pump) 400 uA
Loop Bandwidth 21 Hz Phase Detector Freq 2083.33 MHz
VCO Gain 4.5 kHz/Volt
Reference Clock
Frequency 125 MHz Output Frequency 25 MHz (To PLL 2)
Loop Filter
Components C1_VCXO = 3300
nF C2_VCXO = 10000 nF C2A_VCXO = 10000 nF R2_VCXO = 1 kΩ
Note: PLL Loop Bandwidth is a function of Kφ, Kvco, N as well as loop components. Changing
Kφand N will change the loop bandwidth.

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Copyright © 2013, Texas Instruments Incorporated
PLL2 Loop Filter
Table 5: PLL2 Loop Filter Parameters for LMK04906B
LMK04906B
C1_VCO
0.082
nF
C2_VCO
5.6
nF
C3 (internal)
0.01
nF
C4 (internal)
0.01
nF
R2_VCO
0.68
kΩ
R3 (internal)
0.2
kΩ
R4 (internal)
0.2
kΩ
Charge Pump
Current, Kφ
3.2 mA
Phase
Detector
Frequency
50 MHz
Frequency
2500
MHz
Kvco
18.5
MHz/V
N
50
Phase Margin 69
degree
s
Loop
Bandwidth
132 kHz
Note: PLL Loop Bandwidth is a function of Kφ, Kvco, N as well as loop components. Changing
Kφand N will change the loop bandwidth.

14 SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
Evaluation Board Inputs and Outputs
The following table contains descriptions of the inputs and outputs for the evaluation board.
Unless otherwise noted, the connectors described can be assumed to be populated by default.
Additionally, some applicable CodeLoader programming controls are noted for convenience.
Refer to the LMK04906 Family Datasheet for complete register programming information.
Table 6: Evaluation Board Inputs and Outputs
Connector Name
Signal Type,
Input/Output
Description
Populated:
CLKout0, CLKout0*,
CLKout1, CLKout1*,
CLKout2, CLKout2*,
CLKout3, CLKout3*,
CLKout4, CLKout4*,
CLKout5, CLKout5*
Analog, Output
Clock outputs with programmable output buffers.
The output terminations by default on the evaluation board
are shown below, and the output type selected by default in
CodeLoader is indicated by an asterisk (*):
Clock output pair
Default Board Termination
CLKout0
LVPECL*
CLKout1
LVPECL
CLKout2
LVDS* / LVCMOS
CLKout3
LVDS / LVCMOS
CLKout4
LVDS* / LVCMOS
CLKout5
LVPECL
Each CLKout pair has a programmable LVDS, LVPECL, or
LVCMOS buffer. The output buffer type can be selected in
CodeLoader in the Clock Outputs tab via the
CLKoutX_TYPE control.
All clock outputs are AC-coupled to allow safe testing with
RF test equipment.
All LVPECL clock outputs are source-terminated using 240-
ohm resistors.
If an output pair is programmed to LVCMOS, each output
can be independently configured (normal, inverted, or off/tri-
state).

Revised - December 2013 LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs SNAU126A 15
Copyright © 2013, Texas Instruments Incorporated
Connector Name
Signal Type,
Input/Output
Description
Populated:
OSCout0, OSCout0*,
Analog,
Output
Buffered outputs of OSCin port.
The output terminations on the evaluation board are shown
below, the output type selected by default in CodeLoader is
indicated by an asterisk (*):
OSC output pair
Default Board Termination
OSCout0
LVDS* / LVCMOS
OSCout0 has a programmable LVDS, LVPECL, or LVCMOS
output buffer. The OSCout0 buffer type can be selected in
CodeLoader on the Clock Outputs tab via the
OSCout0_TYPE control.
OSCout0 is AC-coupled to allow safe testing with RF test
equipment.
If OSCout0 is programmed as LVCMOS, each output can be
independently configured (normal, inverted, inverted, and
off/tri-state).
Vcc Power,
Input
Main power supply input for the evaluation board.
A 3.9 V DC power source applied to this SMA will, by
default, source the onboard LDO regulators that power the
inner layer planes that supply the LMK04906B and its
auxiliary circuits (e.g. VCXO).
The LMK04906B contains internal voltage regulators for the
VCO, PLL and other internal blocks. The clock outputs do
not have an internal regulator, so a clean power supply with
sufficient output current capability is required for optimal
performance.
On-board LDO regulators and 0 
r
flexibility to supply and route power to various devices. See
schematics for more details.
Populated:
J1 Power, Input
Alternative power supply input for the evaluation board using
two unshielded wires (Vcc and GND).
Apply power to either Vcc SMA or J1, but not both.
Unpopulated:
VccVCO/Aux Power, Input
Optional Vcc input to power the VCO circuit if separated
voltage rails are needed. The VccVCO/Aux input can power
these circuits directly or supply the on-board LDO
regulators. 0 Ω resistor options provide flexibility to route
power.

16 SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
Connector Name
Signal Type,
Input/Output
Description
Populated:
CLKin0, CLKin0*,
FBCLKin*/CLKin1*
CLKin2, CLKin2*
Not Populated:
FBCLKin/CLKin1
Analog,
Input
Reference Clock Inputs for PLL1 (CLKin0, 1, 2).
CLKin1 can alternatively be used as an External
Feedback Clock Input (FBCLKin) in 0-delay mode
or an RF Input (Fin) in External VCO mode.
Reference Clock Inputs for PLL1 (CLKin0, 1)
FBCLKin/CLKin1* is configured by default for a
single-ended reference clock input from a 50-ohm
source. The non-driven input pin
(FBCLKin/CLKin1) is connected to GND with a 0.1
uF. CLKin0/CLKin0* is configured by default for a
differential reference clock input from a 50-ohm
source.
CLKin1* is the default reference clock input
selected in CodeLoader. The clock input selection
mode can be programmed on the Bits/Pins tab
via the CLKin_Select_MODE control. Refer to the
LMK04906 Family Datasheet section “Input Clock
Switching” for more information.
AC coupled Input Clock Swing Levels
Input
Mode
Min
Max
Units
Differential
Bipolar or
CMOS
0.5
3.1
Vpp
Single
Ended
0.25
2.4
Vpp
External Feedback Input (FBCLKin) for 0-Delay
CLKin1 is shared for use with FBCLKin as an
external feedback clock input to PLL1 for 0-delay
mode. See section, Error! Reference source
not found. Error! Reference source not found.,
for more details on using 0-delay mode with the
evaluation board and the evaluation board
software.
RF Input (Fin) for External VCO
CLKin1 is also shared for use with Fin as an RF
input for external VCO mode using the onboard
VCO footprint (U3) or add-on VCO board. To
enable Dual PLL mode with External VCO, the
following registers must be properly configured in
CodeLoader:
•MODE = (3) Dual PLL, Ext VCO (Fin), (5)
Dual PLL, Ext VCO, 0-Delay, (11) PLL2,
Ext VCO (Fin)

Revised - December 2013 LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs SNAU126A 17
Copyright © 2013, Texas Instruments Incorporated
Connector Name
Signal Type,
Input/Output
Description
Not populated:
OSCin, OSCin* Analog, Input
Feedback VCXO clock input to PLL1 and
Reference clock input to PLL2.
By default, these SMAs are not connected to the
traces going to the OSCin/OSCin* pins of the
LMK04906B. Instead, the single-ended output of
the onboard VCXO (U2) drives the OSCin* input
of the device and the OSCin input of the device is
connected to GND with 0.1 uF.
A VCXO add-on board may be optionally attached
via these SMA connectors with minor modification
to the components going to the OSCin/OSCin*
pins of device. This is useful if the VCXO footprint
does not accommodate the desired VCXO device.
A single-ended or differential signal may be used
to drive the OSCin/OSCin* pins and must be AC
coupled. If operated in single-ended mode, the
unused input must be connected to GND with 0.1
uF.
Refer to the LMK04906 Family Datasheet section
“Electrical Characteristics” for PLL2 Reference
Input (OSCin) specifications.
Test point:
VTUNE1_TP
Analog,
Output
Tuning voltage output from the loop filter for PLL1.
Test point:
VTUNE2_TP
Analog,
Output
Tuning voltage output from the loop filter for PLL2.
Populated:
uWire
Test points:
DATAuWire_TP
CLKuWIRE_TP
LEuWIRE_TP
CMOS,
Input/Output
10-pin header for uWire programming interface
and programmable logic I/O pins for the
LMK04906B.
The uWire interface includes CLKuWire,
DATAuWire, and LEuWire signals.
The programmable logic I/O signals accessible
through this header include: SYNC,
Status_Holdover, Status_LD, Status_CLKin0, and
Status_CLKin1. These logic I/O signals also have
dedicated SMAs and test points.

18 SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
Connector Name
Signal Type,
Input/Output
Description
Test point:
LD_TP
Not populated:
Status_LD
CMOS,
Output
Programmable status output pin. By default, set
to output the digital lock detect status signal for
PLL1 and PLL2 combined.
In the default CodeLoader modes, LED D5 will
illuminate green when PLL lock is detected by the
LMK04906B (output is high) and turn off when
lock is lost (output is low).
The status output signal for the Status_LD pin can
be selected on the Bits/Pins tab via the LD_MUX
control.
Refer to the LMK04906 Family Datasheet section
“Status Pins” and “Digital Lock Detect” for more
information.
Note: Before a high-frequency internal signal (e.g.
PLL divider output signal) is selected by LD_MUX,
it is suggested to first remove the 270 ohm
resistor to prevent the LED from loading the
output.
Test point:
Holdover_TP
CMOS,
Output
Programmable status output pin. By default, set
to the output holdover mode status signal.
In the default CodeLoader mode, LED D8 will
illuminate red when holdover mode is active
(output is high) and turn off when holdover mode
is not active (output is low).
Refer to the LMK04906 Family Datasheet section
“Status Pins” and “Holdover Mode” for more
information.
Note: Before a high-frequency internal signal (e.g.
PLL divider output signal) is selected by
HOLDOVER_MUX, it is suggested to first remove
the 270 ohm resistor to prevent the LED from
loading the output.

Revised - December 2013 LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs SNAU126A 19
Copyright © 2013, Texas Instruments Incorporated
Connector Name
Signal Type,
Input/Output
Description
Test point:
CLKin0_SEL_TP
CLKin1_SEL_TP
CMOS,
Input/Output
Programmable status I/O pins. By default, set as input
pins for controlling input clock switching of CLKin0 and
CLKin1.
These inputs will not be functional because
CLKin_Select_MODE is set to 0 (CLKin0 Manual) by
default in the Bits/Pins tab in CodeLoader. To enable
input clock switching, CLKin_Select_MODE must be 3
or 6 and Status_CLKinX_TYPE must be 0 to 3 (pin
enabled as an input).
Input Clock Switching – Pin Select Mode
When CLKin_SELECT_MODE is 3, the
Status_CLKinX pins select which clock input is active
as follows:
Status_CLKin1
Status_CLKin0
Active Clock
0
0
CLKin0
0
1
CLKin1
1
0
CLKin2
1
1
Holdover
Input Clock Switching – Auto with Pin Select
When CLKin_SELECT_MODE is 6, the active clock is
selected using the Status_CLKinX pins upon an input
clock switch event as follows:
Status_CLKin1 Status_CLKin0
Active
Clock
X
0
CLKin0
1
0
CLKin1
0
0
Reserved
Refer to the LMK04906 Family Datasheet section
“Input Clock Switching” for more information.
Status Outputs
When Status_CLKinX_TYPE is 3 to 6 (pin enabled as
an output), the status output signal for the
corresponding Status_CLKinX pin can be programmed
on the Bits/Pins tab via the Status_CLKinX_MUX
control.
Refer to the LMK04906 Family Datasheet section
“Status Pins” for more information.

20 SNAU126A LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs Revised - December 2013
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Connector Name
Signal Type,
Input/Output
Description
Test point:
SYNC_TP CMOS,
Input/Output
Programmable status I/O pin. By default, set as
an input pin for synchronize the clock outputs with
a fixed and known phase relationship between
each clock output selected for SYNC. A SYNC
event also causes the digital delay values to take
effect.
In the default CodeLoader mode, SYNC will
asserted when the SYNC pin is low and the
outputs to be synchronized will be held in a logic
low state. When SYNC is unasserted, the clock
outputs to be synchronized are activated and will
be initially phase aligned with each other except
for outputs programmed with different digital delay
values.
A SYNC event can also be programmed by
toggling the SYNC_POL_INV bit in the Bits/Pins
tab in CodeLoader.
Refer to the LMK04906 Family Datasheet section
“Clock Output Synchronization” for more
information.
Status Output
When SYNC_MUX is 3 to 6 (pin enabled as
output), a status signal for the SYNC pin can be
selected on the Bits/Pins tab via the SYNC_MUX
control.