Dut Board Design Consideration - Agilent Technologies 93000 SOC Series Training Manual

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DUT Board Design Consideration

Analog signals can be easily disrupted by pulses (for example clocks and
digital signals). To avoid this problem, both signal types must be physically
separated.
Therefore, designing a DUT board for a mixed-signal device requires more
effort than designing a DUT board for a purely digital device.
If you develop a DUT board, you should pay attention to not only the
signals but also the signal return paths (digital ground and analog ground).
General Guidelines
The following issues should always be considered:
If you are using an IC socket, place it at the center of the DUT board. This
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helps to create signal lines of equal length which in turn support identical
travelling times of generated signals, sync pulses, and response signals.
Put a mark at pin 1 of the socket to ensure that the device is always inserted
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correctly.
Take care that input and output signal lines are physically separated (they
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must not be conducted in parallel).
Ensure that relays and active components can be easily replaced. This
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means: Use sockets and mark the correct insertion position.
Problems will occur: Ensure that the DUT board can be easily changed and
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debugged.
Ensure that the required auxiliary components do not interfere with the IC
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handler or waver prober. If possible, consider mounting the components on
the rear of the DUT board.
Additional Mixed-Signal Guidelines
The following issues are essential for mixed-signal devices:
Use two separate and fairly large ground planes for connecting the digital
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and analog ground of the device. On the DUT board, connect the two
ground planes via an inductor. An inductor protects the analog ground from
spikes on the digital ground.
Ensure that all connections between digital and analog signals to their
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respective grounds are as short as possible.
Separate analog and digital signals physically.
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Use impedance-matching coaxial cables at least for all high frequency or
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low amplitude signals. Coaxial cables will shield the signals from radiating
Lesson 2 – DUT Board Design Considerations
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