30
SNAU126A
LMK04906 Family: Low-Noise Clock Jitter with Dual Loop PLLs
Revised - December 2013
Copyright © 2013, Texas Instruments Incorporated
TIP:
Right-clicking any register name in the
Bits/Pins
tab will display a Help prompt
with the register address, data bit location/length, and a brief register description.
Table 9: Register Controls and Descriptions on Bits/Pins tab
Group
Register Name
Description
M
ode C
on
tr
ol
RESET
Resets the device to default register values.
RESET must be cleared for normal operation to
prevent an unintended reset every time R0 is
programmed.
POWERDOWN
Places the device in powerdown mode.
MODE
Selects the operating mode (topology) for the
LMK04906 device.
PD_OSCin
Powers down the OSCin buffer. For use in Clock
Distribution mode if OSCin path is not used.
FEEDBACK_MUX
Selects the feedback source for 0-delay mode.
OSCin_FREQ
Must be set to the OSCin frequency range for
PLL2. Used for proper operation of the internal
VCO calibration routine.
Entering a reference oscillator frequency on PLL2
tab will automatically update OSCin_FREQ to the
proper frequency range.
VCO_MUX
Selects between VCO and VCO divider to drive the
clock distribution path. The VCO divider is only
valid if MODE is selecting the Internal VCO.
uWire_LOCK
When checked, no other uWire programming will
have effect. Must be unchecked to enable uWire
programming of registers R0 to R30.
CL
K
in
CLKin_Select_MODE
Selects operational mode for how the device
selects the reference clock for PLL1.
EN_CLKin1
Enables CLKin1 as a usable reference input during
auto switching mode.
EN_CLKin0
Enables CLKin0 as a usable reference input during
auto switching mode.
CLKinX_BUF_TYPE
Selects the CLKinX input buffer to Bipolar (internal
0 mV offset) or MOS (internal 55 mV offset).
EN_LOS
Enable the Loss-Of-Signal (LOS) detect circuitry.
LOS_TIMEOUT
Sets the timeout value for the LOS detect circuitry
to assert a loss of signal state on a clock input.
Crystal
EN_PLL2_XTAL
Enables Crystal Oscillator
XTAL_LVL
Sets peak amplitude on the tunable crystal.
Values listed are for a 20.48 MHz crystal.
IO C
o
n
tr
o
l
LD_MUX
Sets the selected signal on the Status_LD pin.
LD_TYPE
Sets I/O pin type on the Status_LD pin.
HOLDOVER_MUX
Sets the selected signal on the
Status_HOLDOVER pin.
HOLDOVER_TYPE
Sets I/O pin type on the Status_Holdover pin.