Wordline decoder circuits for embedded charge trap multi-time-programmable-read-only-memory

Abstract

Wordline decoder circuits for an embedded Multi-Time-Read-Only-Memory that includes a plurality of NMOS memory cells coupled to a plurality of wordlines in each row. The wordline decoder circuits control the charge trap behavior of the target NMOS memory array by the mode-dependent wordline high voltage (VWLH) and wordline low voltage (VWLL) trapping the charge in a programming mode by applying an elevated wordline voltage (EWLH) to one of the plurality of WLs, while de-trapping the charge in a reset mode by applying a negative wordline voltage (NWLL) to the entire array. The mode dependent voltage control is realized by switching to couple EWLH to VWLH in a programming mode, otherwise VDD to VWLH, while coupling NWLL to VWLL in a reset mode, otherwise, GND to VWLL. The switch includes plural gated diodes from VWLH with the wordline high protection voltage of VWLH_PR generated by lowering VWLH determined by gated diodes times threshold voltage. The switch includes a series of gated diodes from VWLL with a wordline low protection voltage of VWLL_PR generated by raising VWLL determined by the gated diodes by the threshold voltage, resulting in controlling the WL swing using thin-oxide devices.