Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
1998-11-17
2001-01-30
Metjahic, Safet (Department: 2858)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S652000
Reexamination Certificate
active
06181152
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a testing circuit and, more particularly, to a method and system for testing an integrated circuit with contactless operation.
BACKGROUND OF THE INVENTION
FIG. 1
illustrates a schematic view of a structure of an integrated circuit
1
for contactless operation. This circuit is of a type mounted in contactless chip cards, electronic labels, and other portable devices that work without contact. The circuit
1
comprises an input stage
10
, a rectifier circuit
15
, a demodulator circuit
20
, a modulator circuit
21
, and a central processor unit (CPU)
22
. The CPU
22
comprises, for example, a microprocessor and an EEPROM. The input stage
10
is a parallel resonant circuit comprising an input capacitance C
in
integrated into the silicon, and at least one antenna coil
11
connected to the terminals of the capacitance C
in
by connection pads
12
. The resonant frequency or natural frequency Fp of the input stage
10
is governed by a regulation, and is generally equal to 13.56 MHz.
When the integrated circuit
1
is subjected to an alternating magnetic field Fld with a frequency Fp, an alternating voltage Vac is received in the antenna coil
11
by electromagnetic induction. The alternating magnetic field Fld is emitted, for example, by a station
30
fitted with a coil
31
. This voltage Vac could reach 40 volts and is converted by the rectifier circuit
15
into a direct voltage Vcc for the supply of the integrated circuit. Furthermore, the voltage Vac is demodulated by the circuit
20
for the reception of data DTIN. For the transmission of data DTOUT to the station
30
, the voltage Vac is modulated by the circuit
21
according to the standard technique of load modulation. Naturally, various other standard techniques may be implemented for the reception or transmission of data. For example, techniques using infrared, radioelectric or other signals are acceptable. In every case, however, activation of the integrated circuit
1
by induction requires that the input stage
10
be excited by a magnetic field.
Like other integrated circuits, the contactless circuits are manufactured in batches on a silicon wafer. However, at this stage of manufacture, the input stage
10
is not completed and does not include the antenna coil
11
. It is only after cutting of the wafer that the antenna coil
11
is connected to the capacitance C
in
before the input stage
10
becomes operational. After cutting the wafer, each integrated circuit is individually mounted on a support, such as a plastic card. The integrated circuits are then activated by a magnetic field and electrically tested to eliminate those that are defective.
The manufacturing output values for integrated circuits are mediocre, and a wafer generally contains various circuits that are defective. The sorting out of such defective circuits requires their assembly on supports and their connection to antenna coils. This effort leads to a waste of labor and raw materials which increases the cost of the portable contactless devices. Thus, the present invention proposes to implement a method of testing on wafer to assess the electrical characteristics of contactless circuits before they are cut out from the silicon wafers.
The implementation of an on wafer testing method requires application to the input stage of each circuit a test voltage simulating the alternating voltage Vac received by induction. This test voltage must be about 20 to 40 volts peak-to-peak with a frequency of about 13.56 MHz. Typically, the most efficient HF signal generators available in the market deliver voltages that do not exceed a few volts. They cannot be used to activate integrated circuits working by induction.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method and a system enabling application to the input stage of a contactless integrated circuit of an HF testing voltage that can go up to several tens of volts.
Another object of the of the present invention is to provide a test voltage having a high supply current that can go up to about a hundred milliamperes or more.
These objects are achieved by a method for testing an integrated circuit comprising an input capacitance designed to form, with an antenna coil, a resonant receiver circuit with a predetermined natural frequency. The method is applicable to the integrated circuit before being connected to the antenna coil. The method comprises the steps of connecting the input capacitance of the integrated circuit to a test inductance chosen to form, with the input capacitance, a resonant test circuit having a resonant frequency substantially equal to the natural frequency of the resonant receiver circuit. The resonant test circuit is then excited by an alternating signal through a transformer.
According to one aspect of the invention, a first transformer has at its secondary winding a leakage inductance that forms all or part of the test inductance. The first transformer may be a ring type transformer whose primary and secondary windings do not overlap.
According to yet another aspect of the invention, the test inductance comprises a parasitic inductance of an electrical link between the secondary winding of the first transformer and the input capacitance of the integrated circuit. The secondary winding of the first transformer may be connected to the terminals of the input capacitance by metal tips.
According to still another aspect of the invention, the method is applied to the testing of the input capacitance of the integrated circuit and/or to the testing of means for connecting the input capacitance to an antenna coil. This method comprises the steps of measuring the current that flows through the primary winding of the first transformer and measuring the voltage present across the terminals of the input capacitance.
According to yet another aspect of the invention, the current flowing through the primary winding of the first transformer is measured on the secondary winding of a second transformer whose primary winding is series-connected with the primary winding of the first transformer.
According to another aspect of the invention, the voltage present at the terminals of the input capacitance is measured on the secondary winding of a third transformer whose primary winding is connected to the terminals of the input capacitance.
The present invention also provides for a system to test an integrated circuit comprising an input capacitance designed to form, with an antenna coil, a resonant receiver circuit with a predetermined natural frequency. The system comprises a first transformer connected by its primary winding to a voltage source or alternating current source, and means for connecting the secondary winding of the transformer to the terminals of the input capacitance of the integrated circuit.
According to one aspect of the invention, the first transformer has a leakage inductance at its secondary winding which forms with the input capacitance of the integrated circuit a resonant test circuit whose resonant frequency is substantially equal to the natural frequency of the resonant receiver circuit.
According to another aspect of the invention, the resonant test circuit comprises a parasitic inductance that is present in the connection means.
According to yet another aspect of the invention, the first transformer is a ring type transformer.
According to another aspect of the invention, the connection means comprise a printed circuit card provided with metal tips.
According to still another aspect of the invention, the system comprises means to measure the current flowing through the primary winding of the first transformer and means to measure the voltage present at the terminals of the input capacitance. The means for measuring the current flowing through the primary winding of the first transformer comprises a second transformer whose primary winding is series-connected with the primary winding of the first transformer. The means for measuring the voltage present at the terminals of the input capa
Allen Dyer Doppelt Milbrath & Gilchrist, P.A.
Deb Anjan
Galanthay Theodore E.
Metjahic Safet
STMicroelectronics S.A.
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