a pull up transistor 122 for pulling up to the power supply voltage vcc an isolation control signal isoil in response to the output of the nand gate 112 the other isolation control circuits 200 300 and 400 have the same structure as shown in the drawing referring to fig5 an ispc signal generation circuit for generating the isolation power control signal ispc according to the present invention is illustrated the ispc signal generation circuit includes a level conversion circuit 500 for receiving the burn in mode enable signal pbie during the burn in mode of operation a first output circuit 507 pulls the isolation power control signal ispc to the boost voltage vpp in response to the output of the level conversion circuit 500 an inverter 508 inverts the output of the level conversion circuit 500 and a second output circuit 509 pulls the isolation power control signal ispc to the power supply voltage vcc in response to the output of the inverter 508 the ispc signal generation circuit generates the power supply voltage vcc by the second output circuit 509 during the burn in mode of operation and the boost voltage vpp by the first output circuit 507 during a normal mode of operation with reference to fig6 a and 6b which illustrate the operational timing diagrams of fig4 and 5 operation of the present.