Tektronix 80E07, User Manual, Page: 60 / 72

Reference
46
80E07, 80E08, 80E09, and 80E10 User Manual
Detecting Damaged Inputs
Because of their technology, high-bandwidth sampling modules are vulnerable to
damage through static discharge and overvoltages (EOS) to their inputs. Damage
can occur instantaneously. Under most conditions when EOS damage occurs, the
trace will be flat. It typically involves short-period, high-current discharge. The
damages can be blown diodes as indicated by a large offset or no response to
input.
To check for damage, use one of the following procedures:
H
If checking a TDR capable sampling module, attach a 50
Ω
termination to
the channel input and perform a TDR measurement of the attached fitting.
Adjust the HORIZONTAL SCALE to 500 ns per division. This should
display the entire TDR step from edge to edge. Display the step top at 40 m
ρ
per division and check for flatness. If the top is bowed, sagged, hooked, or
tilted, assume static has damaged the module and service is required. See
Figure 17
.
H
If checking a non-TDR sampling module, use a similar procedure as just
described, but use an external step source.
Figure 17: TDR step of undamaged sampling module
EOS (Electrical Overstress) Prevention
EOS occurs when an electronic device is subjected to an input voltage higher
than its designed maximum tolerable level. Similar to ESD (Electrical Static
Damage), EOS usually is also related to static charges generated by moving
elements. However, unlike ESD that typically deals with thousands of volts,
Checking For Damage