This paper presents a temperature sensor for remote temperature sensing that achieves the required resolution and variation tolerances by: 1) chopping the input current to the remote BJT pair 2) deriving a voltage reference from the same BJTs 3) making multiple current ratio measurements to eliminate parasitic resistance and 4) using digital demodulation to eliminate analog offsets. Besides, trimming a sensor for each hot-spot is costly. Increases in transistor variations and switching noise make static measurements difficult, and having multiple local temperature sensors for each hot-spot location is impractical. The requirements for absolute inaccuracy are modest (≪8☌), but good relative inaccuracy (≪3☌) is needed. Furthermore, in a large multicore microprocessor, multiple-location hot-spot temperature measurements are critical to limit leakage through load balancing. Accurate temperature measurements are required to reliably maximize microprocessor performance under a thermal envelope.
In the multicore era, thermal/power management is essential in order to meet platform-performance and energy-efficiency requirements. Bipolar transistors are so named because the controlled current must go through two types of semiconductor material: P and N.
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