Specifications

145
Chapter 8: Theory of Operation
connector. The mate to this Samtec connector must be designed into and
installed in the system under test. Analysis of single-ended or differential signals
is performed depending on whether the single-ended or differential probe
adapter is used.
A Mictor-compatible probe adapter is also available. Like the Samtec probe
adapter, the Mictor probe adapter is used for single-ended signal analysis through
a Mictor connector designed in and installed into a system under test. Note that
the performance of the logic analyzer module is limited when a Mictor-compatible
probe adapter is used.
A threshold voltage input is provided through the probe adapter and pod for the
user to configure the logic analyzer threshold voltage using the threshold voltage
of the system under test. The logic analyzer module will then utilize the threshold
voltage input to determine the logic high and logic low state of the incoming
signals. The logic analysis system user interface allows the user to select the
threshold voltage input. The threshold voltage input is designed with safeguards
to protect the logic analyzer module from destructive effect of electro-static
discharge (ESD).
The serial I2C lines are used to communicate with the probe adapter for
identification. Periodic polling allows hot insertion of the probe adapter to the
16760A pod. When the probe adapter is installed at the end of the pod, the logic
analyzer module polls the ID of the probe adapter. The module then configures
itself for either single-ended or differential signal analyzer. The serial I2C lines
are also designed with ESD safeguards.
The pods provide a 5 Vdc +
5% auxiliary power to the end of the cable. A thermal
protection circuit senses any over-current and automatically disables the
auxiliary power. The auxiliary power circuit is designed wit safeguards to protect
the logic analyzer module from the effects of electro-mechanical interference
(EMI). Diatonically, a voltage ramp circuit allows an analysis probe to be hot
inserted onto the end of the pod cable. Note that there are currently no analysis
probes or other accessories utilizing this auxiliary power that are designed for the
16760A logic analyzer module as of the printing of this service manual.
Comparators. The comparators are differential input/differential output devices
that interpret the incoming data and clock signals as either high or low. Threshold
voltage, programmed by the user through the user interface, is set by a digital-to-
analog converter (DAC) coupled to the negative side of the differential signal
through a precision resistor. There are separate DAC-driven threshold voltages
for the data and for the clock. In addition, the comparator contains a diode in
which the junction temperature is monitored to ensure the module is being
properly cooled.
Much of the performance optimization for the module is accomplished by the
comparators, including channel delay setting (EyeFinder), programming of input
resistance, and frequency compensation adjustment. Module operation such as