A Fully-Digital BIST Wrapper Based on Ternary Test Stimuli for the Dynamic Test of a 40 nm CMOS 18-bit Stereo Audio $\Sigma\Delta$ ADC

Abstract

This paper proposes a fully-digital BIST architecture for the dynamic test of $\Sigma\Delta$ ADCs. The proposed BIST relies on generating a ternary stream that encodes a high-linearity analog sinusoidal and injecting it directly at the input of the $\Sigma\Delta$ modulator. Compared to the well-known bitstream, the use of three logic levels in the ternary stream reduces the quantization noise and, thereby, results in a test with a higher dynamic range that covers the full scale of the ADC. The output response is analyzed on-chip using a simplified version of the sine-wave fitting algorithm to compute the SNDR. A standard SPI bus provides digital external access to the embedded test instruments. The proposed BIST wrapper has been integrated into a 40 nm CMOS 18-bit stereo audio $\Sigma\Delta$ ADC IP core provided by ST Microelectronics. It incurs an overall area overhead of 7.1% and the total test time is 28 ms per channel. Experimental results on fabricated chips demonstrate an excellent correlation between the BIST and the standard functional specification test.