Circuitry and a method for regulating voltages applied to source and bit lines of a spin-torque magnetoresistive random access memory (ST-MRAM) reduces time-dependent dielectric breakdown stress of the word line transistors. During a read or write operation, only the selected bit lines and source lines are pulled down to a low voltage and/or pulled up to a high voltage depending on the operation (write 0, write 1, and read) being performed. The unselected bit lines and source lines are held at the voltage while separately timed signals pull up or pull down the selected bit lines and source lines during read and write operations.