An 8 µm period bubble memory device with relaxed function designs

A new design concept for 8 μm period bubble memory devices is proposed. Pattern periods and sizes in function designs are increased, keeping the storage cell size 8 μm × 8 μm. This can relax spacial restrictions for the function pattern designs and is remarkably effective in maintaining low drive fields for the functions. Chip organizations which match this function design are discussed and a 256 kbit 8 μm period chip organized with block replicate gates and true swap gates has been designed. The characteristics obtained for the drive field, replicate phase margin, swap current margin, etc., are as good as those of 16 μm period 3 μm bubble devices. A chip organization of a 1 megabit device with a short access time is also proposed.