This is a Basic Flash Memory Programming Voltage Supply circuit. This circuit uses LT1072 switching regulator to generate high voltage by driving the L1. R2 and R2 provide DC feedback for this circuit. R3-C2 and C1 control the SC roll-off. This circuit can generate supply of 12V or 12.75V depended on the R1 values. To protect this circuit from the high command, this circuit uses 5.6V by returning the ouput to 0V. Here is the schematic diagram of the circuit:

Basic Flash Memory Programming Voltage Supply circuit schematic

The zener can be removed if 4.5V minimum output is acceptable. This circuit does not have trimming requirement because it is erased by The combination of LT1072’s tight internal reference and resistor. the trimmer and 1% resistor can be used. During the power down or up, the memory will not damaged because this circuit will not overshoot. The power dissipation of this circuit can be removed by using synchronous switch option. [Circuit’s schematic diagram source: Linear Technology Application Note]