A phase change random access memory on aspect includes a memory cell array block including a plurality of phase change memory cells, a column decoder, a row decoder, a column selector, and a write driver. The memory further includes a write boosting unit having a plurality of internal charge pumps which boost a first voltage to generate a write driving voltage which drives the write driver, where the number of internal charge pumps that are activated during a write operation is varied according to a number of phase change memory cells which are selected during the write operation. The memory still further includes a column boosting unit which boosts the first voltage to generate a column driving voltage which drives the column decoder, and a row boosting unit which boosts the first voltage to generate a row driving voltage which drives the row decoder.