The MAX6655/MAX6656 are precise voltage and temperature monitors. The digital thermometer reports the temperature of two remote sensors and its own die temperature. The remote sensors are diode-connected transistors - typically a low-cost, easily mounted 2N3906 PNP type - that replace conventional thermistors or thermocouples. Remote accuracy is +-1C for multiple transistor manufacturers with no calibration necessary. The remote channels can also measure the die temperature of other ICs, such as microprocessors, that contain a substrate-connected PNP with its collector grounded and its base and emitter available for temperature-sensing purposes. The temperature is digitized with 11-bit resolution. The MAX6655/MAX6656 also measure their own supply
voltage and three external voltages with 8-bit resolution. Each voltage input's sensitivity is set to give approximately 3/4-scale output code when the input voltage is at its nominal value. The MAX6655 operates at +5V supply and its second voltage monitor is 3.3V. The MAX6656 operates on a +3.3V supply and its second voltage monitor is 5V. The 2-wire serial interface accepts standard SMBus Write Byte, Read Byte, Send Byte, and Receive Byte commands to program the alarm thresholds and to read data. The MAX6655/MAX6656 also provide SMBus alert response and timeout functions. The MAX6655/MAX6656 measure automatically and autonomously, with the conversion rate programmable.
The adjustable rate allows the user to control the supply current. In addition to the SMBus ALERT output, the MAX6655/MAX6656 feature an OVERT output, which is used as a temperature reset that remains active only while the temperature is above the maximum temperature limit. The OVERT output is optimal for fan control or for system shutdown.