Tektronix P7313SMA, Technical Reference

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Operating Basics
The P7313SMA probe is designed for compliance testing of high-speed, serial data standards such as PCI Express,
In
fi niBand, SerialATA, XAUI, Gigabit Ethernet, Fibre Channel, and others. All of these high-speed, differential data standards
de fi ne a common-mode voltage less than the +3.6 V/–2.5 V termination range of the P7313SMA probe.
The probe termination voltage can be set to the desired input signal common-mode voltage using one of three control modes:
Auto (the default mode at power-on), Internal, and External. The operation of these modes are described below.
Auto Mode
When the probe is fi rst connected to the oscilloscope, a self test runs, and the default termination voltage control mode
is set to Auto. When the probe is in Auto mode, the common-mode voltage of the input signal is monitored, and the DC
termination voltage is set to match the common-mode input voltage. Auto mode provides the minimum DC loading on the
input signal source.
With open inputs or a high DC source impedance, such as an AC-coupled input signal, the Auto mode select LED fl ashes,
indicating that the termination voltage has been set to zero volts.
This is the mode that you will likely use for most compliance testing of current serial data standards.
Internal (Int) Mode
The internal mode allows you to set the termination voltage with user controls that are available on some TekConnect-interface
oscilloscopes. You can adjust the DC termination voltage within the +3.6 V/–2.5 V range. See your oscilloscope manual for
details on using this mode.
External (Ext) Mode
When the probe is in external mode, it allows control of the DC termination voltage with an external power supply. You can
adjust the DC termination voltage within the +3.6 V/–2.5 V termination voltage range of the probe.
The external DC termination voltage control input is buffered by an internal ampli fi er with 100 K Ω input impedance.
WARNING. Do not exceed the ±15 V maximum external mode voltage for the probe. Excess voltage will damage the probe.
P7313SMA Technical Reference 9