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Test configuration for pins of electrical devices allowing loop-back operation as well as tester communication without changes in the test board

IP.com Disclosure Number: IPCOM000128868D
Original Publication Date: 2005-Oct-25
Included in the Prior Art Database: 2005-Oct-25
Document File: 3 page(s) / 97K

Publishing Venue

Siemens

Related People

Juergen Carstens: CONTACT

Abstract

For testing high speed electronic devices (DUT - Device Under Test) it is common to use a so-called loop-back approach (often also called IO BIST (Input Output Built-In-Self-Test)) for testing of the output driver (output transmitter, Tx) and the input receiver (Rx). The two corresponding device signals (Tx/Rx), which are connected in loop-back configuration, are not accessible to the external tester. In particular, it is not possible to transfer data from the tester to the DUT via the Rx receiver. This yields significant disadvantages for the test execution, e.g. if input pins, needed for starting the test, are already consumed by loop-back wiring, or if loop-back and conventional tests (tester to DUT) have to be performed on the same test board. The following approach potentates to perform a Tx/Rx performance test without high speed test equipment, modifying the IO loop-back test such that tester signals may be injected to the DUT without changing the test board configuration. The idea shows how to implement a loop-back configuration covering all pins even if the number of transmitters is different to the number of receivers. Therefore, a passive resistive network (power-splitter) on the load board close to the DUT is introduced. Resultants are the following advantages:

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Test configuration for pins of electrical devices allowing loop-back operation as well as tester communication without changes in the test board

Idea: Dr. Wolfgang Spirkl, DE-Munich

For testing high speed electronic devices (DUT - Device Under Test) it is common to use a so-called loop-back approach (often also called IO BIST (Input Output Built-In-Self-Test)) for testing of the output driver (output transmitter, Tx) and the input receiver (Rx). The two corresponding device signals (Tx/Rx), which are connected in loop-back configuration, are not accessible to the external tester. In particular, it is not possible to transfer data from the tester to the DUT via the Rx receiver. This yields significant disadvantages for the test execution, e.g. if input pins, needed for starting the test, are already consumed by loop-back wiring, or if loop-back and conventional tests (tester to DUT) have to be performed on the same test board.

The following approach potentates to perform a Tx/Rx performance test without high speed test equipment, modifying the IO loop-back test such that tester signals may be injected to the DUT without changing the test board configuration.

The idea shows how to implement a loop-back configuration covering all pins even if the number of transmitters is different to the number of receivers. Therefore, a passive resistive network (power- splitter) on the load board close to the DUT is introduced. Resultants are the following advantages:

1. The receivers being subjected to loop-back wiring are accessible to the external tester.

2. The resistive network reduces the voltage swing at the input of Rx. In loop-back tests this is desirable.

3. Neither load board changes nor relays are needed during the test.

4. The approach is flexible enough to implement all-pin loop-back approaches even for cases where a strong mismatch in the number of transmitters and receivers is present (see DRAM example below).

In Fig. 1 the basic configuration is shown with a resistive divider that loops back the Tx signal to the receiver Rx. The receiver's input voltage is

[R1*V(Tx) + R2*V(tester)] / (R1+R2).

Two different operation modes are possible:

a) If Tx is off (high impedance), it follows that R2 has a very large value, and the receiver's voltage is equal to the tester's voltage with a little bandwidth reduction due to the additional parasitic capacitance from Tx. The input of Rx is fully controllable. For example it is to perform accurate DC (Direct Current) measurements.

b) If Tx is enabled, loop back operation from Tx to Rx is possible. The Tx signal is fed back to R...