Device for switching higher supply voltage for use in read-only memory store, comprising circuit for subjecting drop in gate voltage of switching transistor to voltage of output line

摘要

The switching device comprises a voltage-shift type switching circuit for switching a higher supply voltage (HV) on at least one output line (L1) of capacitve type, a transistor (M30) for switching a lower supply voltage Vcc(V1) on the same output line, and a control circuit (4) for controlling the drop of the gate voltage of the switching transistor (M30) from the higher supply voltage to the ground potential subjected to the drop of the output line voltage from the higher supply voltage in the lower supply voltage. The switchihng circuit comprises two branches; the first branch comprising a loading transistor (M10) connected to the higher supply voltage terminal (HV), a switching transistor (M13) connected to the ground and receiving as the gate voltage the inverse of control voltage (CTRL), one or more cascade transistors (M11,M12) connected between the two transistors, and a repeater transistor (M40) connected in series in the same branch and associated with the output line by the intermediary of node (N11) providing the gate signal to the lower supply voltage switching transistor (M30) directly connected to the output line; the second branch comprises a set of transistors starting with a loading transistor (M20); and a transistor (M50) is connected as a resistor between the two branches for favouring the polarization of the cascade transistors. The voltage-shift circuit (40) applies a biasing voltage (Vbias2) as the gate voltage to the repeater transistor (M40) of the first branch of the switching circuit. The circuit (40) comprises two branches; the first branch comprises a transistor (M41) with the gate and the drain connected together to a polarization node providing the first biasing voltage (Vbias1) and a transistor (M42) connected as a diode; the second branch comprises a transistor (M43) connected as a current mirror with the transistor (M41) of the first branch, and a set of transistors (M44,M45) connected as diodes between the transistor (M43) and the output line. The lower supply voltage (V1) is equal to the logic supply voltage (Vcr). In the second embodiment, the switching device comprises a supplementary loading transistor connected between the higher supply voltage terminal and the output line, and is controlled by the same signal as the loading transistor of the first branch of the switching circuit. The integrated circuit comprises the switching device associated with at least one current-conducting output line. The integrated circuit of a read-only memory store has output lines which are the lines for selecting memory cells. The memory store is of type FAMOS or FLASH-EPROM, and the selection lines are for rows of memory cells.