4Kbit Microwire EEPROM in an 8-MSOP
The ROHM BR93G66FVM-3AGTTR is a 4Kbit serial EEPROM using the Microwire interface, organized as 256 words by 16 bits.
Supply range and bus timing
The 1.7 V minimum supply is the key differentiator here — this EEPROM stays alive during a deep brown-out on a 3.3 V rail, and it can be powered directly from a 1.8 V MCU I/O bank. The 3 MHz clock is the Microwire bus speed; at 1.7 V the AC timing margins tighten, so keep the bus capacitance low and the trace short. The 5 ms write cycle time (word or page) sets the firmware polling interval — after a write command the host must wait at least 5 ms before addressing the part again.
ROHM lists the BR93G66FVM-3AGTTR as Active. That means the part is still in regular production, no last-time-buy notice, no EOL clock ticking. For procurement, this is a clean line item — no single-source flag, no allocation risk from a phase-out. The part is ROHS3 compliant.
Second-source and density options
The closest drop-in sibling is the BR93G46FVM-3AGTTR — same package, same 3 MHz clock, same supply range, but 1Kbit organized as 64 x 16. If the BOM needs more storage, the BR93H86RF-WCE2 offers 16Kbit (1K x 16) but runs at 1.25 MHz and requires 2.7 V minimum, so it is not a pin-for-pin swap without a layout and firmware update. For an automotive-grade variant, the BR93A46RFVT-WME2 is AEC-Q100 qualified, 1Kbit, 2 MHz, 2.5 V min, and rated to 105°C.