The MAX6690 is an accurate digital thermometer that reports the temperature of the remote P-N junction and its own mold. Using a small 16-pin QSOP surface-mount package, the remote junction can be a diode-connected transistor -- usually a low cost, easy to install 2N3904 NPN type or 2N3906 PNP type -- in place of a traditional thermistor or thermocouple.
Typical Operating Circuit
Remote accuracy is ±2°C for multiple transistor manufacturers, no calibration required. The remote junction may also be a common collector PNP, such as a substrate PNP for a microprocessor (µP). The 2-wire serial interface accepts standard system management bus (SMBusTM), write byte, read byte, send byte, and receive byte commands to program alarm thresholds and read temperature data.
Pin Configuration
Measurement can be done automatically and autonomously, with conversion rates programmed by the user, or programmed to operate in single shot mode. The adjustable conversion rate allows users to optimize the power supply current and temperature update rate to match system requirements. When the conversion rate is faster than 1Hz, the conversion result is available as a 7-bit plus byte of 1°C LSB. When the rate is lower than 1Hz, the MAX6690 enters expansion mode. In this mode, there are three additional bits of temperature data in the extended resolution register, providing 10-bit plus resolution and 0.125°C LSB.
Typical Operating Characteristics
The resolution per LSB for a single shot conversion is also 0.125°C at a conversion rate of 1Hz or slower. Parasitic Resistance Offset (PRC) mode can also invoke a conversion rate of 1Hz or slower by setting bit 4 of the configuration register to 1. In PRC mode, the effect of the series resistance on the external diode leads is cancelled out. 11 bit conversion in PRC mode in < 500ms: Disable when the conversion rate is higher than 1Hz. A conversion is also 11 bits < 500 ms. MAX6690 The default low-temperature measurement limit is 0 ° C. This can be extended to -64°C by setting bit 5 of the configuration register to 1.
Functional Diagram
Features
● High Accuracy ±2°C (max) from +70°C to +100°C (Remote)
● 11-Bit, 0.125°C Resolution
● Dual Channel: Measures Remote and Local Temperature
● No Calibration Required
● Programmable Under/Overtemperature Alarms
● I2C-Compatible/SMBus Interface
● +3V to +5.5V Supply Range
Applications
● Desktop Computers
● Notebook Computers
● Servers
● Thin Clients
● Workstations
● Test and Measurement
● Multichip Modules
