AN202 View Datasheet(PDF) - Philips Electronics
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Description
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AN202 Datasheet PDF : 5 Pages
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Philips Semiconductors
Testing and specifying FAST logic
Application note
AN202
AC TEST LOADS FOR THE
PHILIPS SEMICONDUCTORS JIG
As stated previously, the Network Analyzer was also used to design
and optimize AC test loads to be used with the universal jig. FAST
product loads require 50pF load capacitance and 500Ω resistance to
ground.
Philips Semiconductors meets the 50pF requirement through the
use of a 45pF load, 4pF jig capacitance, and 3pF probe
capacitance. The result, 52pF, is slightly more stringent than
required.
A few words about load capacitors are in order. All capacitors have
an associated inductance. Due to this inductance, a capacitor will
form a series resonant circuit at some frequency. For single 50pF
capacitors, this typically occurs between 200 and 600MHz
depending on the type of capacitor. Above this resonant frequency,
the capacitor has inductive characteristics and does not present a
capacitive load. this is very important with FAST because harmonics
due to the sharp edge transition rates occur at 600MHz and above.
The Philips Semiconductors FAST loads solve this problem by
reducing the load capacitor lead inductance by paralleling three
15pF chip capacitors. The resulting load is 45pF. At the same time,
since smaller value caps are used to build up the capacitive load,
the associated series resonant point is above 1.2GHz.
The load resistors are 1/8W selected 510Ω ± 10Ω chip resistors.
The entire load assembly is constructed on the jig PCB along with
the input termination, and the jumpers which select an input or
output path. The load circuit is detailed on the FAST data sheets for
3-State parts.
CORRELATION
While numerous ATE systems are available and are very efficient, it
is imperative that the ATE correlate to a user’s bench setup. Since
the Philips Semiconductors FAST parts are all characterized on the
setup described in this note, it is just as important that the user’s
bench jigs meet the same performance criteria. Without similar jigs,
it will be very difficult to correlate AC data.
June 1987
Figure 3.
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