The ADM1031 is an ACPI-compliant, three-channel digital thermometer and under/over temperature alarm for use in personal computers and thermal management systems. Optimized for the Pentium III, the part offers a 1C higher accuracy, which allows system designers to safely reduce temperature guardbanding and increase system performance. Two PWM fan control outputs control the speed of two cooling fans by varying output duty cycle. Duty cycle values between 33% and 100% allow smooth control of the fans. The speed of each fan can be monitored via TACH inputs, which can be reprogrammed as analog inputs to allow speeds for 2-wire fans to be measured via sense resistors. The device also detects a stalled fan. A dedicated fan speed control loop provides control without the intervention of CPU software. It also ensures that if the CPU or system locks up, each fan can still be controlled based on temperature measurements, and the fan speed is adjusted to correct any changes in system temperature. Fan speed can also be controlled using existing ACPI software. Two inputs (four pins) are dedicated to remote temperaturesensing diodes with an accuracy of 1C, and an on-chip temperature sensor allows ambient temperature to be monitored. The device has a programmable INT output to indicate error conditions, and a dedicated FAN_FAULT output to signal fan failure. The THERM pin is a fail-safe output for overtemperature conditions that can be used to throttle a CPU clock.