1 Kbit I2C EEPROM for parameter storage
The Microchip 24LC21A/SN is a 1 Kbit serial EEPROM organized as 128 x 8 bits, communicating over an I2C bus at up to 400 kHz. It stores configuration data, calibration constants, or small lookup tables in a non-volatile memory that retains content without power. The 900 ns access time is the read-cycle window the master must respect; at 400 kHz the bus clock period is 2.5 µs, so the EEPROM's output data is valid well within one clock cycle, leaving margin for bus capacitance and trace delay.
Write cycle time and endurance considerations
Firmware must poll the acknowledge polling or wait the full 10 ms before initiating the next write.
Housed in an 8-pin SOIC with 3.90 mm body width (the 0.154" narrow SOIC), surface-mount soldered directly to the PCB. The tube shipment is typical for engineering samples or low-volume production; for reel quantities, check the alternate 24LC21A/SN-G or similar tape-and-reel suffix variants.