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ChronosGUI
Table 1
lists the various menu items in this screen.
Table 1. Software Settings Description
Section
Function
VCO Select
Selects between VCO1 and VCO2. Only one VCO can be used
during operation. See
CDCE421 data sheet
for VCO tuning ranges.
Prescalar
The prescalar selection is determined in conjunction with VCO and
output divider selection. See the
CDCE421 data sheet
to determine
the proper setting.
Output Divider
The output divider is determined in conjunction with the VCO and
prescalar settings. See the
CDCE421 data sheet
to determine the
proper setting.
Driver Select
Selects between LVPECL or LVDS output.
PECL Config
This option should be activated when using LVPECL output. When
selected, the USB controller enables the onboard LVPECL
termination.
Charge Pump Current
Selects appropriate charge pump current. See
Figure 6
and
Figure 7
for recommended configurations.
Loop Filter Bias Select
Bias 0 should be used at all times. Bias 1 is a test mode reserved for
factory use.
Loop Filter
Selects the loop filter C and R values. See
Figure 6
and
Figure 7
for
recommended configurations.
VCO Calibration
When Enable VCO Calibration is selected, the CDCE421 uses its
internal calibration circuit to lock the PLL loop. VCO Calibration
Override should not be checked. TI uses manual calibration for test
modes.
TI Test Use
Setting should be kept at
0000 ibias_100ua
. Other settings are for
TI use only.
Chronos IC Config
Select Use U13 programming socket for rapid programming of
Chronos-enabled devices.
Select Use U8 DIE/U9 QFN socket if the EVM is using a
direct-mounted die or a QFN-mounted device (typical configuration).
Select Use U12XTAL EVAL if using the optional 6-pin XO mounting
pads (for Chronos-enabled oscillators).
Chronos Control
Select Enable Power to run the entire board from the host USB
voltage. In this mode, the EVM does not need an external 3.3V
power supply. If this option is not selected, then an external 3.3V
supply and ground connection must be attached.
Select Output Enable to provide a clock output. When not selected,
the output goes to a high-Z state.
Push Write Chronos settings to RAM to download settings into the
CDCE421 on-chip volatile SRAM. These settings are lost upon
device power-down.
Push Write Chronos settings to EEPROM NO LOCKING when ready
to store the configuration in the CDCE421 nonvolatile EEPROM. The
settings are available after device power-down. The settings can be
changed at a later time.
Push Write Chronos settings to EEPROM LOCKING only if the
settings are permanent and final. After this selection, the
EEPROM is locked and cannot be altered at a later time.
USB Communication
A bright red light indicates that USB is not connected or not
communicating properly. A green light indicates that a proper USB
connection exists.
10.9MHz–1175MHz Low Phase Noise Clock Evaluation Board
12
SCAU020 – March 2007
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