Stanford Research Systems CG635, User Manual

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Operation 18
CG635 Synthesized Clock Generator
The user can easily switch between five standard output voltage levels by pressing the
CMOS
Ÿ
and
ź
keys in the OUTPUT LEVELS section of the front panel. When the
CMOS output is at a standard level, the CG635 will highlight the appropriate standard
level LED. The meaning of the five standard levels is summarized in the Table 9.
Table 9: CMOS Standard Output Levels
Label Description V
HIGH
(V) V
LOW
(V)
+5.0V 5 V CMOS 5.00 0.00
+3.3V 3.3 V CMOS 3.30 0.00
+2.5V 2.5 V CMOS 2.50 0.00
+1.8V 1.8 V CMOS 1.80 0.00
+1.2V 1.2 V CMOS 1.20 0.00
V
HIGH
and V
LOW
indicate the voltage driven by the CMOS output for the high and low
logic levels, respectively.
The user also has the ability to set the CMOS output to nonstandard levels. When the
output differs from the standard levels, the CMOS VAR LED in the OUTPUT LEVELS
section will turn on. In this case, the highlighted standard LED indicates the standard
level nearest the current output level. Pressing the CMOS
Ÿ
and
ź
keys when the VAR
LED is on will force the outputs to the nearest standard level in the direction indicated by
the key.
The voltages for CMOS high and low states can be viewed in the main display by
pressing ‘CMOS HIGH’ and ‘CMOS LOW’ keys in the DISPLAY section of the
front panel.
The CMOS high and low voltages may be set to arbitrary values, or stepped up and down
by configurable step sizes by following the instructions described in the Front-Panel User
Interface section at the beginning of this chapter. However, the limits summarized in
Table 10 apply.
Table 10: Limits for CMOS High and Low Voltages
Parameter Minimum Maximum Resolution
CMOS HIGH (V
HIGH
) –0.50 V 6.00 V 0.01 V
CMOS LOW (V
LOW
) –1.00 V 1.00 V 0.01 V
CMOS Amplitude(V
HIGH
–V
LOW
) 0.50 V 6.00 V 0.01 V
If the user tries to enter a value that violates the V
HIGH
or V
LOW
limit, the CG635 will
briefly display “Volt Error” and leave the current value unchanged. However, if the user
tries to enter a value that is valid in terms of the limits on V
HIGH
and V
LOW
, but violates
the amplitude limit, the CG635 will change both the requested voltage and its
complement. The requested voltage will be set to the desired level, and the
complementary voltage will be adjusted to satisfy the amplitude limits. The CG635 will
briefly display “lo is N.NN” or “hi is N.NN” to indicate the new complementary voltage
level. If V
HIGH
– V
LOW
would be > 6.00 V, V
LOW
will be set 6.00 V below V
HIGH
or V
HIGH
will be set 6.00 V above V
LOW
. If V
HIGH
– V
LOW
would be < 0.50 V, V
LOW
will be set
0.50 V below V
HIGH
or V
HIGH
will be set 0.50 V above V
LOW
.