Texas Instruments SCAU020 manual Software Settings Description, Section Function

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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.

12 10.9MHz–1175MHz Low Phase Noise Clock Evaluation Board SCAU020 –March 2007

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