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STTS2004：2.2 V memory module temperature sensor with a 4 Kb SPD EEPROM

The STTS2004 is targeted for DDR4 DIMM modules in servers, desktops, and mobile personal computing platforms (laptops and other industrial applications). The thermal sensor (TS) in the STTS2004 is compliant with the JEDEC specification TSE2004a2, which defines memory module thermal sensor requirements for use in DRAM DIMMs (Dual Inline Memory Modules) with Serial Presence Detect (SPD), in which all the information concerning the DRAM module configuration (such as access speed, size, and organization) can be kept write-protected in one or more of the blocks of memory. The 4-Kbit serial EEPROM (SPD) in the STTS2004 is organized as two pages of 256 bytes each, or 512 bytes of total memory. Each page is comprised of two 128-byte blocks. The SPD is able to selectively lock the data in any or all of the four 128-byte blocks. The STTS2004 can interface to buses which have multiple devices on a shared bus, and each device has its own unique address on this bus. The device can achieve substantial power savings by using the software-programmed shutdown mode.

The TS-SPD EEPROM combination provides space as well as cost savings for mobile and server platform dual inline memory modules (DIMM) manufacturers, as it is packaged in the compact 2 mm x 3 mm 8-lead TDFN package with a thinner maximum height of 0.80 mm. The DN package is compliant to JEDEC MO-229, variation W2030D.

The digital temperature sensor has a programmable 9-12 bit analog-to-digital converter (ADC) which monitors and digitizes the temperature to a resolution of up to 0.0625 °C. The default resolution is 0.25 °C/LSB (10-bit). The typical accuracies over these temperature ranges are: ±2 °C over the full temperature measurement range of –20 °C to 125 °C, ±1 °C in the +40 °C to +125 °C active temperature range, and ±0.5 °C in the +75 °C to +95 °C monitor temperature range.

The temperature sensor in the STTS2004 is specified for operating at supply voltages from 2.2 V to 3.6 V. Operating at 3.3 V, the typical supply current is 160 μA (includes I²C communication current).

The on-board sigma-delta ADC converts the measured temperature to a digital value that is calibrated in °C. For Fahrenheit applications, a lookup table or conversion routine is required. The STTS2004 is factory-calibrated and requires no external components to measure temperature.

The digital temperature sensor component has user-programmable registers that provide the capabilities for DIMM temperature-sensing applications. The open drain event output pin is active when the monitoring temperature exceeds a programmable limit, or it falls above or below an alarm window. The user has the option to set the event output as a critical temperature output. This pin can be configured to operate in either a comparator mode for thermostat operation or in interrupt mode.

The STTS2004 is protocol-compatible with the 2 Kbit SPD in the STTS2002 and uses a page selection method which is applied to the lower or upper pages of the 4 Kbit SPD. Unlike the STTS2002, the STTS2004 does not support the Permanently Set Write Protect (PSWP) feature.

Locking a 128-byte block of the EEPROM is accomplished by using a software write protection mechanism in conjunction with a high input voltage V_HVon the A0 input pin. A specific I²C sequence is used to protect each block from writes until write protection is electrically reversed using a separate I²C sequence which also requires V_HVon input A0 pin of the device.

Write protection for all four blocks is cleared simultaneously, and write protection may be re-asserted after being cleared.

Key Features

• 2.2 V memory module temperature sensor with integrated 4 Kb SPD EEPROM
• Fully compliant with JEDEC TSE2004B2 specifications
• Operating temperature range: –20 °C to +125 °C
• Single supply voltage 2.2 V to 3.6 V
• 2 mm x 3 mm TDFN8, height: 0.80 mm (max): JEDEC MO-229, W2030D compliant and RoHS compliant, halogen-free
• Temperature sensor
  • Temperature sensor resolution: programmable (9-12 bits) 0.25 °C (typ)/LSB - (10-bit) default
  • Temperature sensor accuracy (max) of: ± 1 °C (from +75 °C to +95 °C); ± 2 °C (from +40 °C to +125 °C); ± 3 °C (from –20 °C to +125 °C)
  • ADC conversion time: 125 ms (max) / 70 ms (typ) at default resolution (10-bit)
  • Typical operating supply current 160 μA (EEPROM standby)
  • Temperature hysteresis selectable set points from 0, 1.5, 3, 6.0 °C
• 4 Kb SPD EEPROM
  • Functionality identical to ST’s M34E04 SPD EEPROM
  • 4 Kbits organized as two pages of 256 bytes each
  • Each page is composed of two 128-byte blocks
  • Software data protection for each 128-byte block
  • Byte Write within 5 ms
  • 16 bytes Page Write within 5 ms
  • More than 1 million write cycles
  • More than 40-year data retention
• Two-wire bus
  • Two-wire I2 C compatible serial interface
  • Supports up to 1 MHz transfer rate (I2 C Fast Mode+)
  • Does not initiate clock stretching
  • Supports SMBus timeout 25 ms - 35 ms

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