Performance Evaluation
48
CG635 Synthesized Clock Generator
Table 18: Power-On Self Tests
Test
Description
Test Fail Symptoms
ROM
ROM checksum
Flash memory is corrupted. Unit may behave
unpredictably
1
24V Power
Power supply is not providing stable 24 volts.
2
19.44 MHz tuning
The crystal can’t tune to ±100 ppm. The CG635 may
not be able to lock at all frequencies.
3
19.40 MHz tuning
The crystal can’t tune to ±100 ppm. The CG635 may
not be able to lock at all frequencies.
4
RF VCO
The VCO can’t tune from 960MHz to 2.05 GHz. The
CG635 may not be able to lock at all frequencies.
5
CMOS output
The CG635 is unable to drive the front-panel CMOS
output to the correct voltage. Check that the output is
not connected to a voltage source.
6
Q / Q
¯ outputs
The CG635 is unable to drive the Q/Q
¯ outputs to the
correct voltages. Check that the outputs are terminated
into 50
and not connected to a voltage source.
7
Clock symmetry
Output duty cycle is not 50 %. Output driver may be
damaged.
8
Option detection
Optional oscillator is installed, but not oscillating. The
CG635 will use its internal oscillator.
The CG635 self test is automatically executed at power-on. It may also be executed by
sending the command
*TST?
over the remote interface. If the unit passes it will return 0
over the remote interface. If it fails, it will return 72. Refer to the user guide for more
information about communicating with the CG635 over a remote interface.
Output Level Tests
The output level tests are intended to test the accuracy and integrity of the CG635 output
drivers. They test the accuracy of the DC voltage levels at each of the supported
communication standards. They also test the speed with which transitions between levels
occurs.
Q/Q
¯ Level Tests
The Q/Q
¯ ouput level tests require the setup shown in Figure 4.
Figure 4: Q/Q
¯ output level test setup
The Q/Q
¯ outputs should be terminated into 50
. The terminator connected to the Agilent
DVM should be accurate to 1%. To test the Q output, configure the CG635 as follows:
1.
Press ‘SHIFT’, ‘INIT’, ‘Hz’ to return the CG635 to default settings.
Q
Q
CMOS
CG635
Agilent 34401A
6½ Digit DVM
50
Ω
termination
50
Ω
termination
