A simple built-in current sensor for IDDQ testing of CMOS data converters

This paper presents a simple built-in current sensor (BICS) design for quiescent current (IDDQ) testing of CMOS data converter circuits. The proposed BICS works in two modes: the normal mode and the test mode. In the normal mode, the BICS is isolated from the circuit under test (CUT) due to which there is no performance degradation of the circuit. In the testing mode, the BICS detects the abnormal current caused by permanent manufacturing defects and has negligible impact on the performance of the circuit under test. The dynamic current of the CUT does not affect the BICS output. The BICS is operated from power supply voltages of the CUT using the current reference configuration. A 10-bit charge scaling digital-to-analog converter and a first-order modulator of an 8-bit sigma delta analog-to-digital converter have been designed in standard 1.5 μm CMOS and tested using the present BICS for injected faults simulating manufacturing defects. It is shown that significant improvement in testing of mixed signal integrated circuits has been achieved using a simple fault injection technique combined with the BICS.