4 Mbit async SRAM for the byte-wide bus
The 1.65V to 2.2V supply range places this squarely in the 1.8V logic ecosystem — common in battery-powered handhelds, portable instruments, and low-power industrial controllers.
15 ns access — timing margin for the board
In a typical 8-bit microcontroller system with a 40 MHz bus clock (25 ns period), a 15 ns access leaves 10 ns of margin for address decoding, PCB trace delay, and setup time at the memory controller. That margin shrinks if the board uses multiple chip-select gates or long traces — but for a single-device layout within 100 mm of the controller, 15 ns is comfortable. If your bus runs at 66 MHz (15 ns period), the 15 ns access leaves zero margin for decode logic; you would need a faster SRAM or a pipelined bus.
512K x 8 organization — byte-wide fit
The 512K x 8 organization (byte-wide data bus) is the natural fit for 8-bit microcontrollers (e.g., 8051, AVR, PIC18) that need external data memory. For 16-bit or 32-bit processors, two of these devices can be paired — one for the low byte, one for the high byte — with shared address lines and separate chip enables.