AVTECH ELECTROSYSTEMS AVRQ-4-B, Instructions Manual

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The battery occupies a relatively large portion of the top side of the standard
daughterboard. It may be necessary to locate the footprints for large SMT DUTs (e.g., 32-
pin SOICs) on the bottom side of the PCB. It may also be possible to mount the battery
vertically to provide more DUT space on the top side.
Do not use coin batteries to power the floating side of the DUT. They are normally
severely restricted in their output current rating and can not supply the 2-20 mA
typically required to power the floating side of the DUT, regardless of their mA·hr rating.
The A23-style 12V battery has an appropriate combination of voltage output, current
rating, and physical size.
The sample daughterboard uses a simple DIP socket for the DUT, rather than the more
convenient ZIF-style of socket. This is done because ZIF sockets have higher parasitic
capacitance between the various pins, which can be very harmful to the DUT's CMTI
performance. Avoid ZIF sockets for the DUT.
DIFFERENTIAL PROBING
The mainframe uses a two-pin header near the DUT area door to transmit the output
waveform to a user-supplied Tektronix P6246 differential probe. The use of a differential
probe helps reduce spurious transient signal artefacts on the oscilloscope, which are
typically caused by ground bounce and interference in general.
When designing custom daughterboards, a similar approach should be used.
Please note that the P6246 has a maximum differential input voltage range of 7V. If higher
values of VCC2 will be used, a different probe will be required. Other probes may be used
by installing a matching two-pin socket as an extender.
INSTALLING THE DAUGHTERBOARDS
To install a daughterboard, first turn off the instrument. (The instrument will disable the
high-voltage circuitry automatically if the DUT door is opened, but it is better practice to
turn off the instrument entirely.)
Install the desired 8-pin DIP device in the DIP socket on the loose daughterboard.
If necessary for input biasing and/or VCC1 generation, install an A23-type battery on the
daughterboard. Confirm that it is generating >6V once it is installed in the battery holder.
Open the rear-panel DUT door.
Carefully lower the daughterboard into the pin sockets, aligning the pins as shown in the
image on page 35. Press the daughterboard into the socketing.
Close the DUT door. Turn on the instrument and proceed with your tests.
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