Thermal Management - English (1st edition):Using multichannel temperature sensors
to save space and cost When a circuit board includes multiple hot spots, standard practice is to monitor the temperatures of those locations to avoid performance degradation and even catastrophic failure.A conventional approach is shown in Figure 1, where a sensor is placed near each hot spot. Monitoring board hot spots can be done with standard local sensors (TS5–TS8). If a thermally sensitive component has a temperature-sensing transistor (also called a “thermal diode”) integrated on the die of a high-temperature IC, a remote-temperature sensor can use the IC’s thermal diode to accurately measure its die temperature (TS1–TS4).Figure 2 shows the same board, but in this case a single multichannel sensor IC monitors all of the hot spots. The circuit uses the MAX6581* (also see Figure 3), which can measure up to seven external temperatures as well as its own temperature. The device can monitor temperatures on ASICs, CPUs, and FPGAs using thermal diodes, or it can measure board hot spots using discrete diode-connected transistors and the internal local sensor.Using a single IC to monitor several locations reduces sensor cost. It also simplifies the design by allowing several channels of temperature data to be read from a single I2C slave address.