Product category:
Sensors and Data Acquisition
News Release from: STMicroelectronics | Subject: STTS424 and STTS424E02
Edited by the Electronicstalk Editorial
Team on 05 September 2007
Temperature sensors protect PCs
The STTS424 is a stand-alone digital temperature sensor, while the STTS424E02 integrates the temperature sensor with a 2Kbit serial presence detect (SPD) EEPROM.
STMicroelectronics has released two digital temperature sensor chips that comply with the Jedec JC42.4 specification They are intended for monitoring the temperature of the DIMMs (dual in-line memory modules) used in personal computers
This article was originally published on Electronicstalk on 8 Nov 2004 at 8.00am (UK)
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The faster DDR2 and DDR3 (double-data-rate) DRAM memories installed in computers and other systems increase the risk of memory overheating, so temperature sensing, which allows the CPU to regulate the speed of the memory traffic or take further action to prevent overheating, has become more important in system design.
The STTS424 is a stand-alone digital temperature sensor, while the STTS424E02 integrates the temperature sensor with a 2Kbit serial presence detect (SPD) EEPROM that is used on DIMMs to store timing parameters and other information about the module, in accordance with Jedec requirements.
Both devices communicate with the CPU chipset through an I2C/SMBus-compatible serial bus, and are available in 2 x 3mm DFN8 and 4.4 x 3mm TSSOP8 packages.
The STTS424 sensor has a 50% lower operating current than competitive devices and the Jedec JC42.4 standard.
The integrated STTS424E02 can replace the 2Kbit SPD EEPROM of existing memory module implementations, thereby adding a temperature sensing capability with minimum board redesign cost, and with no increase in the number of components.
For programming ease, the temperature sensor and the EEPROM in the STTS424E02 each have their own I2C/SMBus address.
The new sensor chips integrate an analogue-to-digital convertor (ADC) which monitors and digitises the temperature with a resolution down to 0.25C, and an accuracy of +/- 1C, over the 75 to 95C temperature range.
The devices are factory calibrated and require no external components for temperature measurement.
They can operate on a supply voltage from 2.7V to 3.6V, and over a -40 to +125C temperature range.
The typical supply current at 3.3V is 100uA.
An open-drain EVENT output pin is active either if the monitored temperature exceeds a programmed limit or if it strays outside the upper or lower limit of a customer-programmed alarm window.
The pin can be configured to operate either in a comparator mode for thermostat operation, or in the interrupt mode.
The 2Kbit serial EEPROM in the STTS424E02 can permanently lock the data in the first 128byte, for use in DDR DIMMs with SPD.
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