High Density EEPROM Memories with Fast Serial Interface

SGS-THOMSON Microelectronics has introduced a family of high speed, high density serial EEPROMs compatible with all four modes of the Motorola SPI bus. The ST95010/11, ST95020/21, ST95040/41 and ST95080 are 1Kbit, 2Kbit, 4Kbit and 8Kbit devices organized as 128x8, 256x8, 512x8 and 1024x8, respectively, and their key features include both hardware and software write protection mechanisms, 2MHz clock frequency and excellent erase/write endurance.

The Serial Peripheral Interface (SPI) protocol defines a 3-wire bus (Serial Clock, Serial Data In and Serial Data Out) and the ST950xx family supports clock rates up to 2MHz. The ST950xx family supports all of the defined SPI clock modes; positive SPI clock modes are supported by ST950x0 devices, while the ST950x1 parts support negative SPI clock modes. A device connected to the SPI bus is selected when the Chip Select pin is brought low and a /HOLD pin allows communications between the selected EEPROM and the bus master to be interrupted without resetting the serial sequence.

The SP950xx family incorporates self-timed programming with a maximum erase/write cycle time of 10ms. To protect against spurious write operations, a Write Protect pin (/W) is provided; no programming cycle can be initiated while /W is low. In addition, two non-volatile status bits allow the whole memory, the upper half, the upper quarter or none of the memory to be selectively write- protected, while a page write mode allows up to 16 bytes to be programmed in one operation.

Other features of the new family include operation from a single 4.5 to 5.5V supply, ESD protection to 4000V (Human Body Model), DIP8 and SO8 package options, and a minimum data retention of ten years. Typical applications include automotive and telecom products, especially those using single-chip microcontrollers, where the SPI interface allows high speed data transfer with as few as four I/O pins.

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