AVTECH ELECTROSYSTEMS AVRQ-4-B, Instructions Manual

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DO NOT CONNECT COAXIAL CABLING TO THIS OUTPUT. The capacitance
of the cabling will reduce the dV/dt rates noticeably.
11.LOGIC OUT Connector s . There are two possible positions where the logic probe can
be connected, “A” and “B”.
“A” is a two-pin header connector mounted on the motherboard. It connects internally
to the logic output of the DUT (and the associated ground). This is the output that is
normally monitored for “glitches” caused by high dV/dt rates on the common mode
voltage. It will mate directly to the Tektronix P6246 differential probe, or to standard
0.1” header sockets. When using the differential probe, install the probe so that the “-”
side is on the left, and the “+” side is on the right. A differential probe is used to help
eliminate noise coupled from the high-voltage signals. Please note that the P6246 has
a maximum differential input voltage range of 7V. If higher values of VCC2 are used, a
different probe will be required. Since it is mounted on the motherboard, it is affected
by the small parasitic inductance in the socketing arrangement. In demanding test
scenarios, it may be preferable to connect to probe points on the daughterboard
instead. “B” is provided for this purpose.
“B” provides access to the two-pin header connector mounted on the daughterboard.
By default, the sample daughterboards as shipped from the factory do not have this
two-pin header connected to any signals. They must be configured with appropriate
resistors and/or capacitors to enable this mode of operation. The “B” connector can be
configured with resistive divider circuits on the daughterboard, allowing a low-voltage
differential probe (like the P6246) to be used with a higher VCC2.
It is best to avoid measuring the low-voltage LOGIC OUT signal at the same time as a
probe is connected to the HV PULSE signal. Inter-channel interference in the probes
and oscilloscope may introduce significant noise on the low-voltage signal. Instead,
measure the signals separately, and use the memory storage function of the
oscilloscope if you wish to combine the signals on a single image.
12.V CC2 OUT Connector . (Optional feature. Present on units with the -V2 option only.)
This output is wired in parallel with the VCC2 connection on the DUT socket, and may
be used for monitoring purposes.
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