Word line overdrive in memory and method therefor

Abstract

Higher word line voltages facilitate write operations in spin-torque magnetic memory devices, but overdriving the gate of a selection transistor with such higher word line voltages can damage the selection transistor if the gate-to-source voltage for the selection transistor is too high. Therefore in order to support the word line voltage needed on the gate of the select transistor for an up-current write operation without exceeding limits on the gate-to-source voltage for the select transistor, the gate of the selection transistor can be driven in a two-step process. The gate of the selection transistor is first driven to a lower voltage within the limits of the gate-to-source voltage for the transistor when the source of the transistor is grounded or at a voltage near ground. A voltage is then applied across the memory cell, which results in the source of the selection transistor being raised above its initial ground or near-ground state. After the source of the selection transistor has been raised, the gate voltage of the selection transistor can also be raised at least as much as the source of the selection transistor has been elevated without violating the limits on the gate-to-source voltage for the selection transistor.