Temp-Log 3 Click is a temperature measuring Click board™ featuring the MCP9843 IC, an accurate temperature sensor IC with integrated EEPROM. Besides the thermal sensor, this IC is equipped with additional 256 bytes of EEPROM. This can be a very useful option for some applications: it allows any data to be stored within the same IC, so no additional EEPROM IC is required. This can simplify the design, reducing the number of additional components. The thermal sensor itself includes some great features such as the programmable interrupt engine, measurement range from -20°C to +125°C, accuracy up to ±1°C typically, and more.
Temp-Log 3 Click is supported by a mikroSDK compliant library, which includes functions that simplify software development.
The MCP9843 IC meets JEDEC specification JC42.4-TSE3000B3 and JC42.4-TSE2002B3, allowing it to be used as a thermal sensor for memory modules. The MCP9843 is designed specifically for DRAM DIMMs (Dual In-line Memory Modules), allowing the Serial Presence Detect (SPD) feature. However, its use is not limited only to memory modules. The presence of EEPROM can be utilized for many different tasks: recording of temperature peaks, storage of various thermal event alerts, and similar. This makes Temp-Log 3 a great choice for development of various embedded applications based on temperature measurement and data logging.
Temp-Log 3 Click is equipped with the MCP9843 IC, a temperature sensor with EEPROM, by Microchip. This IC is used to convert the temperature measurement into digital information. Besides the thermal sensor, this IC also features 256 bytes of EEPROM on the same die. It is compliant with the JEDEC specification JC42.4-TSE3000B3 and JC42.4-TSE2002B3 since it is designed specifically for DRAM DIMMs (Dual In-line Memory Modules), allowing the Serial Presence Detect (SPD) feature. However, it is not limited only to this role: it can be used as a very accurate general-purpose thermometer with the added benefit of integrated EEPROM, reducing the number of physical ICs required to design a temperature logging application. Temp-Log 3 Click utilizes the I2C serial interface (SMBus compatible), which allows it to be used in a wide range of applications.
The temperature sensor section includes all the features typically found on such ICs. Most of its interrupt engine features are very similar (or identical) to features found in Thermo 8 Click, which is based on the MCP9808 IC. This includes the interrupt and thermometer modes, alert pin configuration, hysteresis of the temperature thresholds, critical temperature alert feature, and so on. The EVENT pin of the IC is routed to the INT pin of the Click board™. It is pulled to a HIGH logic level by a resistor, so the polarity should be programmed accordingly, the same as in the case of Thermo 8 Click. However, there are some minor differences including the EEPROM section, which will be discussed.
The MCP9843 features the CAPABILITIES register, unlike the MCP9808 IC. This register is a read-only register and it provides some general information, such as the factory-specified accuracy in the upper-temperature range (+75°C to +95°C and +40°C to +125°C), measurement range, resolution, and other parameters of the sensor. Its description, along with the description of other registers, can be found in the MCP9843 datasheet.
Although the output temperature register is of the same width as the one used in MCP9808 (16 bits), there are 12 bits of thermal data available along with the sign bit, in the 2’s complement format. All the user-configurable registers in the MCP9843 are 16 bits wide. However, not all 16 bits are used, in most cases.
Both the temperature and the EEPROM section have their own I2C address. The I2C address is determined by four fixed bit values, while the last three bits (LSBs) are determined by the logic states applied to A2, A1, and A0. While A2 and A1 address are hard-wired to a LOW logic level on this Click board™, the value of the A0 address bit can be changed by switching the SMD jumper labeled as ADDR SEL to either 0 (tied to GND) or 1 (tied to VCC). The datasheet of the MCP9843 offers a table with the content of these four bits for each section of the IC.
By switching the SMD jumper labeled as VCC SEL, the logic voltage level of the I2C bus can be selected between 3.3V and 5V. This allows Temp-Log 3 Click to be interfaced with both 3.3V and 5V MCUs. Note, however, that the MCP9843 is supplied with power from the mikroBUS™ 3.3V rail, regardless of the VCC SEL jumper position.
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