Process Variation-Aware Multiple-Fault Diagnosis of Thermometer-Coded Current-Steering DACs

Abstract

Abstract-In this paper, we first introduce a process-variation aware test-point generation method. With this method, faults are not obscured by process variations and we are able to generate new test points by measuring a very limited number of current values on-chip and estimating values of the remaining currents. We furthermore introduce a multiple-fault diagnosis procedure where we use the process-variation aware test-point generation method. The proposed methods can also be used for structural test. For the application, we have used a thermometer coded current steering (TCCS) digital to analog converter, as they are widely used due to their suitability for high speed applications and the symmetric design is suitable for the application of our method. We introduce a DFT hardware for the diagnosis cost reduction, while implementing our methods. Experimental results show that parametric errors as small as 20% can be diagnosed with up to 97.8% accuracy.

A Model for Temperature Insensitive Trimmable MOSFET Current Sources

“…The temperature dependence of arises from the temperature dependence of the mobility [11], which has the form (2) where is the carrier mobility at temperature and is the process dependent mobility temperature exponent.…”

“…One of the main performance limitations when manufacturing this type of DAC in a CMOS process is the mismatch between individual current sources, which are a potential source of nonlinearities in the DAC response. These problems can be reduced by various techniques such as using a combination of large devices and very careful layout [1], fault diagnosis [2], random switching [3] or continuous trimming [4]. However, the improved performance is only achieved at the expense of increasing die area and/or power consumption.…”