Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2001-12-12
2003-10-21
Cuneo, Kamand (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C439S638000
Reexamination Certificate
active
06636058
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to signal probe adapters and more particularly to a adapter for connecting multi-channel, low input capacitance signal probes of a measurement test instrument, such as logic analyzers and the like, to multi-channel controlled impedance connector mounted on a device under test.
Logic analyzers have long been used to acquire multiple signals from a device under test to analyze and verify timing, detect glitches, and the like. Multi-channel signal probes couple signals to the device under test from the instrument and from the device under test to the instrument. Various types of connectors are provided on the device under test, such as a microprocessor mother board, for connecting the signal probes to the device being tested. Rows of square pin connectors have traditionally been used as the interface contacts between the device under test and the probes.
The increased speed of digital circuitry requires the use of connectors having high speed, controlled impedance transmission lines. One such connector is called a mictor connector, manufactured by Tyco Electronics, Corp., Harrisburg, Pa. A mictor connector is a high speed, controlled impedance connector having a plug and closely mating receptacle. Each plug and receptacle portion is configured for either 0.025 inch or 0.050 inch center line spacing of transmission lines and contain from 38 to 266 lines. The transmission lines are aligned in parallel rows on either side of center power ground connector. The center ground connector in the plug is a corrugated planar structure that mates with vertically positioned ground leads in the receptacle. The transmission lines in the plug and receptacle are contained in mating housings. Mictor connectors have both vertically and horizontally mounted plugs and receptacles. The ends of the transmission lines extending from the bottom of the vertically mounted plug or receptacle are bent at an angle to form contact pads for soldering to contact pads on the surface of a circuit board or the like. The ends of the transmission lines of the horizontally mounted plug or receptacle extend directly outward from the bottom of the plug or receptacle for soldering to contact pads formed on opposing surfaces of the circuit board or the like at the edge of the board. The ends of the transmission lines at the other end of the housing of the plug or receptacle form electrical contacts that mate with each other when the closely mating plug and receptacle are connected together. In logic analyzer probing applications, a 38 pin mictor connector is most often used. Up to 38 circuit board runs of the device under test are laid out in pattern that terminate in a pattern corresponding to the pattern of the pins on the mictor connectors. The mictor receptacle is soldered to conductive pads that terminate the runs. In most probing applications of microprocessor boards, multiple mictor connectors are mounted on the circuit board. The multi-channel logic analyzer probe head has the mating mictor plug. The transmission lines of the mictor plug are electrically coupled to center conductors of a multiple coaxial cable type ribbon cable. Electrical elements, such as resistors, may be included in the probe head to provide electrical isolation for the device under test.
The P6434 34-channel high density probe, manufactured and sold by Tektronix, Inc., Beaverton, Oreg., for use with the TLA family of logic analyzers is an example of a logic analyzer probe using mictor connectors. The P6434 probe head uses an edge mounted mictor connector that is soldered to contact pads on opposing sides of a circuit board. The circuit board has an additional row of interconnect contact pads formed on each opposing side of the circuit board that are electrically connected via conductive runs to the soldered contact pads of the mictor connector. The mictor connector and circuit board are inserted into a holder that also receives two probe cables. The probe cables are ribbon type cables having multiple lead wires. The lead wires of each probe cable are soldered to contact pads of a circuit board. The contact pads are electrically connected via conductive runs to another set of contact pads that match the interconnect contact pads of the mictor connector circuit board. The conductive runs preferably include resistive elements. The probe cable circuit boards are positioned on the mictor connector circuit board with electrically conductive elastomer contacts electrically connecting the contact pads on the probe cable circuit board to the interconnect contact pads of the mictor connector circuit board. The circuit boards and the mictor connector are secured in place in a housing made of opposing half shells that are screwed together.
There are drawbacks to using mictor connectors and similar type connectors, such as Samtec connectors, for high speed probing applications. The transmission lines of the mictor connector adds capacitive loading to the device under test which affects the fidelity of the signal being acquired. The input capacitance of the mictor connector/probe head combination can be in the range of 2 to 2.5 picofarads. The mictor connectors are permanently mounted on the circuit board, which increases the cost of board, especially when multiple mictor connectors are used. Additionally, the complexity of the device under test board layout is increased because of the need to layout trace runs to each of the mictor connector, which may result in sacrificing board space that may otherwise be used for component layout.
What is needed is a multi-channel, low input capacitance signal probe head for devices under test that reduces the capacitive loading associated with previous types of probe heads using existing high density connectors. In addition, the multi-channel, low input capacitance probe head should eliminate the need for permanently mounted connectors on circuit boards of the device under test. Further, the multi-channel, low input capacitance probe head should provide flexibility in device under test board layout. There is also a need for adapters that connect existing connectors to the new multi-channel, low input capacitance signal probe head and existing multi-channel probe heads to the new connecting elements on the device under test.
SUMMARY OF THE INVENTION
Accordingly, the present invention is to an adapter for connecting a multi-channel, low input capacitance signal probe to a multi-channel controlled impedance connector mounted on a device under test. The signal probe has a signal probe head having at least a first substrate having a plurality of input signal pads formed and exposed at one end of the substrate. The substrate is positioned in a housing having at least a first open end and a substrate support member that receives the substrate such that the input signal pads are exposed at the open of the housing. A removable signal contact holder mounts to the housing and supports electrically conductive elastomer signal contacts. The holder is disposed over the open end the housing such that the elastomer signal contacts engage the input signal pads. The multi-channel low input capacitance signal probe head is preferably configured with a second substrate having a plurality of input signal pads formed and exposed at one end of the substrate. The substrate support member receives the second substrate such that the support member is disposed between the first and second substrate and the input signal pads on the second substrate are exposed at the open end of the housing.
The housing preferably has opposing sidewalls walls separated by opposing front and back walls with each sidewall having a latching recess formed therein adjacent to the open end of the housing. The housing has bores formed on either side of the substrate that are perpendicular to the open end of the housing. The housing is preferably configured with a substrate carrier and a substrate carrier cover. The substrate carrier forms the substrate support member that receives the substrate with t
Bucher William K.
Cuneo Kamand
Tang Minh N.
Tektronix Inc.
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