Write-inhibit circuit, semiconductor integrated circuit using the same, ink cartridge including the semiconductor integrated circuit, and ink-jet recording apparatus

摘要

Chip area and operating current is reduced in a chip having a write-inhibit circuit that uses a data-writing request signal WR and a write-control signal WRITE to inhibit data writing. By comparing a reference current Iref and a drive current ID, a current-mirror circuit CM can monitor the voltage of a power supply VDD. When the voltage of the power supply VDD is sufficiently high, the data-writing request signal WR is unchanged. Conversely, when the voltage of the power supply VDD is not sufficiently high, a transistor T6 producing reference-current I_D and a buffer B2 cause the write-control signal to be low L irrespective of whether the data-writing request signal WR is at H or at L. Thus, miswriting can be prevented when the power-supply voltage decreases, since writing by the data-writing request signal WR is impossible.