High Speed On-Chip Signal Generation for Debug and Diagnosis

This article presents methods and circuits for synthesizing test signals in the time/frequency domain. An arbitrary signal is first encoded using sigma–delta modulation in the digital amplitude-domain and converted to the time or frequency domain through a digital-to-time converter (DTC) or digital-to-frequency converter (DFC) operation realized in software. In hardware, the resulting bit-stream is inputted cyclically to a high-order phase-locked loop (PLL) behaving as a time-mode reconstruction filter in the appropriate domain (time or frequency). A high-speed prototype implementation consisting of a 4th order PLL built in 0.13 μm complementary metal oxide semiconductor (CMOS) process with an off-chip loop filter has been fabricated and used to generate signals at 4 GHz. The digital nature and portability of the phase/ frequency test signal generation process makes the proposed scheme compatible with the IEEE 1149.1 test bus standard and easily amenable to any testing environment: production, characterization, design-fortest (DFT), or built-in self-test (BIST).