DIMM thermal watchdog with on-chip EEPROM
The STTS2004B2DN3F is a temperature monitoring system from STMicroelectronics built specifically for DIMM DDR memory modules. It integrates a sigma-delta ADC, a register bank, and 4 Kbit of EEPROM — the EEPROM holds the module's SPD (Serial Presence Detect) data, while the sensor tracks the DIMM's thermal state and reports it over a 2-wire I²C bus. Accuracy is rated at ±3°C maximum across the full -20°C to 125°C sensing range, which covers the operating envelope of server, workstation, and desktop DIMMs. The supply rail accepts 2.2V to 3.6V, letting it run directly from a 3.3V or 2.5V DIMM power plane without an extra LDO. Packaged in an 8-TDFN with exposed pad (2x3 mm footprint), it mounts flush on the DIMM PCB — surface-mount only, no through-hole option. The part is active in ST's portfolio and ROHS3 compliant.
What the ±3°C accuracy means for the BOM
A ±3°C maximum error is the thermal tolerance your system sees at the worst-case corner — not a typical figure, but the guaranteed limit over temperature and supply.
I²C interface and DIMM compatibility
Communication is 2-wire I²C, the same bus used by the DIMM's SPD EEPROM. The STTS2004B2DN3F shares the I²C bus with the SPD data — the sensor has its own I²C address, so no collision. The part is designed for DDR memory modules, but the evidence does not specify DDR3, DDR4, or DDR5 explicitly; the supply range and temperature range are compatible with all three. The on-chip EEPROM stores the SPD content, so this single IC replaces a separate EEPROM plus a temperature sensor — a BOM consolidation move for memory module makers.
It is ROHS3 compliant. For a DIMM module builder or a server OEM qualifying this into a BOM, the active status means no forced redesign cycle.