Analysis and Reduction of Supply Noise Fluctuations Induced by Embedded Via-Programming ROM

Various input addresses and accessed code-patterns of a via-programming read only memory (ROM) cause substantial fluctuations in peak current and supply noise across cycles. This work analyzes the fluctuations in the supply noise that are associated with the pattern-dependent current profile of embedded via-programming ROM on a QFN package with various decoupling capacitances. A pattern-insensitive (PI) technique is developed for via-programming ROM to reduce both fluctuations of peak current and cycle current across various input addresses and accessed code-patterns. The PI technique involves the arranging of the data patterns of a ROM-code and the adjustment of the structures of row decoders and peripheral circuits. Experiments based on the designed test-setup on fabricated 0.25 mum 256 kb ROM macros demonstrate the fluctuation in peak current of conventional ROM and its reduction by the PI technique. The fluctuations of measured peak and cycle currents of PI-ROM are only 0.7% and 13.1% of those of conventional ROM. The PI-ROM also has a 94.5% lower standby current than conventional ROM.