AutoFocus User’s Guide
11
©1989-2018 Lauterbach GmbH
External Termination PCB (shipped before 2006)
Most AutoFocus preprocessors shipped in 2005 came with two pairs of termination daughter PCBs. One
pair labeled “1.5 … 5 V”, the other labeled “1.5 … 3.3 V’ or “1.5 … 2.5 V” for early versions of the
preprocessor.
How to choose the proper termination PCB:
•
Complete range version (1.5 … 5 V)
The complete range version cuts the signal amplitude roughly in half. Hence it is save to use,
even for 5 V targets, but it might not be optimal for target voltages below 2.5 V.
•
Low voltage version (1.5 … 3.3 V or 1.5 … 2.5 V)
The low voltage version does not affect the signal amplitude significantly. This module usually
shows better results in terms of data eye width, especially for target voltages below 2.5 V. For
early versions of this termination module, the signal amplitude after the termination PCB was
conservatively specified for a maximum of 2.5 ,V which is why these modules were labeled
“1.5 … 2.5 V”. As more data became known, the maximum voltage could be increased to 3.3 V,
so this module is now labeled “1.5 … 3.3 V”.
You must not use the low-voltage termination for target voltages above 3.3 V!
Termination PCB (shipped after 2006)
•
Integrated low-voltage termination (1.5 … 3.3 V)
The low-voltage termination is now integrated in the main PCB. For target voltages greater 3.3 V
a voltage converter (LA-7922) has to be used. However, this voltage converter might reduce the
maximum trace frequency. You should always contact [email protected] to
discuss solutions for target voltages outside the specified range of 1.8 … 3.3 V or if you require a
customized termination module.
Don’t connect any JTAG signals on the trace connector if a separate debug
connector is used. Electrical reflections will impact the JTAG communication.
The preprocessor itself does not use any JTAG-signal, they are simply routed to the
back end connector.
Termination daughter PCB
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