AT21CS11Microchip TechnologySerial EEPROM · SOIC-8AT21CS11 is a Microchip Technology 1-Kbit (128 x 8) single-wire, I/O-powered serial EEPROM with a unique factory-programmed 64-bit serial number — for identifying and authenticating remote items such as cartridges, cables and disposable attachments where only two wires (SI/O plus ground) can reach the device. The single-wire interface is the selection point: one SI/O pin carries both power (drawn from the pull-up) and data, so a detachable accessory needs no extra connector pins, battery or regulator — and the 2.7 V to 4.5 V self-powered range suits Li-ion-powered devices, versus the AT21CS01 which covers 1.7 V to 3.6 V. It runs up to 125 kbps in high-speed mode, with 8-byte page writes, a 5 ms self-timed write cycle, 1,000,000 write-cycle endurance, 100-year data retention, IEC 61000-4-2 Level 4 ESD protection, and -40°C to +85°C operation. Four 256-bit zones can each be permanently locked read-only, and the 256-bit security register carries the factory serial number plus user-programmable lockable bytes, which is what makes the part an anti-counterfeit and warranty-tracking device rather than a plain memory. Selection advice: choose AT21CS11 over AT21CS01 when the pull-up rail is 2.7 V to 4.5 V; choose it over a 2-wire I2C EEPROM when pin count, connector cost or detachable-assembly simplicity matters more than bus speed. The base MPN covers several packages (2-pad XSFN, 3-lead SOT-23, 8-lead SOIC, 4-ball WLCSP), so quote the full ordering code (e.g. SSH10 for SOIC-8) to match your footprint and assembly process. Featured on Mouser New Products (2026-10-15). Parameters verified against Microchip Technology documentation. State quantity, packing and date-code requirements in your RFQ; we reconfirm the offered lot before quotation and reply within 24 hours.