MICROCHIP 25LC256-I/SN

The 25XX256 are 256k-bit Serial Electrically Erasable PROMs. The memory is accessed via a simple Serial Peripheral Interface (SPI) compatible serial bus. The bus signals required are a clock input (SCK) plus separate data in (SI) and data out (SO) lines. Access to the device is controlled through a Chip Select (CS) input. Communication to the device can be paused via the hold pin (HOLD). While the device is paused, transitions on its inputs will be ignored, with the exception of Chip Select, allowing the host to service higher priority interrupts. The 25XX256 is available in standard packages including 8-lead PDIP and SOIC, and advanced packaging including 8-lead DFN and 8-lead TSSOP. Pb-free (Pure Sn) finish is also available.

The 25XX256 is a 32768 byte Serial EEPROM designed to interface directly with the Serial Peripheral Interface (SPI) port of many of today’s popular microcontroller families. It may also interface with microcontrollers that do not have a built-in SPI port by using discrete I/O lines programmed properly in firmware to match the SPI protocol. The 25XX256 contains an 8-bit instruction register. The device is accessed via the SI pin, with data being clocked in on the rising edge of SCK. The CS pin must be low and the HOLD pin must be high for the entire operation. Data (SI) is sampled on the first rising edge of SCK after CS goes low. If the clock line is shared with other peripheral devices on the SPI bus, the user can assert the HOLD input and place the 25XX256 in ‘HOLD’ mode. After releasing the HOLD pin, operation will resume from the point when the HOLD was asserted.

The device is selected by pulling CS low. The 8-bit read instruction is transmitted to the 25XX256 followed by the 16-bit address, with the first MSB of the address being a don’t care bit. After the correct read instruction and address are sent, the data stored in the memory at the selected address is shifted out on the SO pin. The data stored in the memory at the next address can be read sequentially by continuing to provide clock pulses. The internal address pointer is automatically incremented to the next higher address after each byte of data is shifted out. When the highest address is reached (7FFFh), the address counter rolls over to address 0000h allowing the read cycle to be continued indefinitely. The read operation is terminated by raising the CS pin.

• Max. clock 10 MHz
• Low-power CMOS technology - Max. Write Current: 5 mA at 5.5V, 10 MHz - Read Current: 5 mA at 5.5V, 10 MHz - Standby Current: 1 μA at 5.5V
• 32,768x8-bit organization
• 64 byte page
• Self-timed ERASE and WRITE cycles (5 ms max.)
• Block write protection - Protect none, 1/4, 1/2 or all of array
• Built-in write protection - Power-on/off data protection circuitry - Write enable latch - Write-protect pin
• Sequential read
• High reliability Endurance: 1,000,000 erase/write cycles - Data retention: >200 years - ESD protection: >4000 V
• Temperature ranges supported; - Industrial (I): -40℃ to +85℃ - Automotive (E): -40℃ to +125℃
• Standard and Pb-free packages available