Die having embedded circuitry with test and test enable circuitry
Timely testing of die on wafer reduces the cost to manufacture ICs. This disclosure describes a die test structure and process to reduce test time by adding test pads on the top surface of the die. The added test pads allow a tester to probe and test more circuits within the die simultaneously. Also, the added test pads contribute to a reduction in the amount of test wiring overhead traditionally required to access and test circuits within a die, thus reducing die size.
1. A die of semiconductor material, comprising:
A. die pads arranged at the periphery of the die;
B. an embedded circuit having functional inputs and outputs, at least one of the functional inputs and outputs being unconnected to a die pad, the embedded circuit also having a test enable input;
C. test pads;
D. first test circuitry connected between the at least one of the functional outputs and a first test pad; and
E. test enable circuitry having an input connected to an enable test pad, separate from the first test pad, and an output connected to the test enable input.
2. The die of claim 1 in which functional inputs and outputs of the embedded circuit, other than the at least one of the functional inputs and outputs, are connected with the die pads.
3. The die of claim 1 in which the embedded circuit is one of a digital signal processor core, a microprocessor core, mixed signal circuitry, peripheral circuitry, and memory circuitry.
4. The die of claim 1 in which the test pads carry only test signals and provide no functional communication to circuits external the die.