1Kbit EEPROM with 1-Wire interface — TO-92-3 package
The DS2431+T&R is a 1Kbit non-volatile EEPROM from Analog Devices, organized as 256 x 4 bits and accessed over a single-contact 1-Wire bus. The 2 µs access time means the host microcontroller reads or writes a byte within a few microseconds after the bus command completes — fast enough for calibration constants, serialization data, or small lookup tables that must survive power loss. No external Vcc is required for the EEPROM core; the 1-Wire master provides both communication and operating current through the data line pull-up resistor.
Listed as Active by Analog Devices with ROHS3 compliance. The EEPROM retains data for a minimum of 10 years at 85°C per the datasheet endurance specification.
1-Wire bus integration — what the 2 µs access means
The 1-Wire interface uses a single data line with an open-drain master and an external pull-up resistor (typically 4.7 kΩ for standard speed). The 2 µs access time is the time from the end of a read command to the data being available on the bus — it sets the minimum slot time for the master's bit-bang or UART-based protocol. For a microcontroller running at 16 MHz, this is about 32 instruction cycles; the firmware must not poll faster than the EEPROM can respond. Memory organization is 256 x 4 bits — four pages of 64 bytes each. The 4-bit wide internal architecture means the host reads or writes in byte-aligned chunks; the upper nibble of each byte is stored in a separate array. This is transparent to the 1-Wire command set but matters for wear-leveling: each page has a 100k erase/write cycle endurance, so a calibration constant updated every minute lasts about 69 days on one page before the first page wears out.