Planar Semiconductor Temperature Sensor for Automotive Applications

The theory of silicon temperature sensor and the design of a planar sensing chip are discussed. The temperature-resistance function is essentially logarithmic with a TCR of 0.7%/°C near room temperature. Nominal, polarity-independent resistance values (@ 25°C) from 100 to 5000 ohms are attainable; the discussion, however, will be restricted to 1.0 and 3.3 K ohm devices. Resistance-temperature characteristics of planar silicon sensors are compared to those of currently available metal-wire sensors and thermistors. Due to the small size of the actual sensing chip (15 x 15 x 6 mil³) the heat-transfer characteristics of the sensor are determined almost entirely by the packaging configuration; thermal response and dissipation data are presented for an axial-lead glass diode package and a plastic (Silect^T) transistor package and comparison is made with the characteristics of conventional silicon sensors. The use of the silicon sensor in automotive applications is briefly discussed.

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