Built-In Binary Code Inversion Technique for On-Chip Flash Memory Sense Amplifier With Reduced Read Current Consumption

Abstract

The bit-line sense amplifier (S/A) for on-chip flash memory compares cell current with reference current to identify data that are programmed. The S/A for 0 (erased) cell data consumes a large sink current, which is greater than off-current for 1 (programmed) cell data. This brief proposes a built-in write/read path based on binary inversion methods to reduce the sensing current of S/A. An original binary code is programmed into flash memory with an inverted binary code based on the proposed bit inversion techniques. The de-inversion hardware, which is implemented with small logic gates to restore original binary data, only consumes logic current instead of analog sink current in the S/A. The proposed techniques are evaluated for the DSPStone benchmark and are applied to the modified S/A for ARM Cortex-M3-based microcontroller with 128-kB on-chip flash memory based on a 0.18-um EEPROM technology. The circuit-level simulation result for the DSPStone benchmark shows that a newly implemented chip with the S/A based on the proposed technique consumes approximately less than 22% of the operating power that conventional S/A uses.