Tektronix DTG5078, User Manual

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Timing Parameters
1-42
DTG5078 & DTG5274 & DTG5334 Data Timing Generator User Manual 2
Figure 1-27: Selecting a clock source
External PLL Input Specifies that the external signal connected to PHASE LOCK IN is used
as the input signal to the PLL circuit.
You can use the following signals: Frequency range 1 to 200 MHz, Input
voltage swing 0.2 to 3 Vp-p, Maximum input voltage
±
10 V, Impedance
50
Ω
, and AC coupled.
When you use the External PLL Input signal, the DTG5000 software
measures the frequency of the input signal and shows the result in PLL
Input: in the Timing window. The output frequency basically varies in
steps of the amount that is n times larger than the frequency of the
External PLL Input signal. The step size varies, depending on the data
format and Long Delay On/Off setting.
External Clock Input Specifies that the external clock signal is fully used as the clock signal.
You can use the following signals: Frequency range 1 to 750 MHz for
DTG5078 (1 MHz to 2.7 GHz for DTG5274), Input voltage swing 0.2 to
2 Vp-p, Duty cycle 50
±
10%, Impedance 50
Ω
, and AC coupled.
When you use the External Clock Input signal, the DTG5000 software
measures the frequency of the input signal and shows the result in Clock
Input: in the Timing window. The output frequency is basically fixed to
the frequency of the External Clock Input signal. However, it varies,
depending on the data format or Long Delay On/Off setting.
Table 1-7: Clock source (cont.)
Clock Source Description
10MHz Ref
Ext 10MHz Ref In
DDS
Divider
Ext PLL In
PLL
Ext Clock In
Internal
H/W Clock