As techniques for fabricating integrated circuits have advanced, the number of circuit components in integrated circuits has increased dramatically. It is well known that the increase in the number of circuit components placed on integrated circuits has led to an increase in temperature generated by such circuits.
Temperature gradients across the dies of conventional high performance very large scale integration (VLSI) components, such as a microprocessor, can adversely affect component performance. For example, a temperature variation between two clock driver circuits within a microprocessor often results in a skew in the system clock of the microprocessor. Moreover, the die of the microprocessor may reach an unacceptable temperature that causes the microprocessor to malfunction or stop functioning.
Many of the currently used sensing devices for monitoring temperature are based on bipolar devices. The base-emitter voltage of bipolar devices, however, does not scale in the same manner as the threshold of metal oxide semiconductor transistors used in many current integrated circuits. For example, many current CMOS devices operate with power supply voltage levels of less than 1 Volt and devices will operate with even lower voltages in the near future. Eventually, the supply voltages of these devices will be lower than the 0.4–0.5 Volt required to provide a forward bias for a conventional diode. Nonetheless, most prior art solutions for monitoring temperature involve bipolar devices because the base emitter voltage is typically more controlled.
In view of the shortcomings of the prior art, there is a need for a technique for monitoring temperatures in integrated circuits without the need for bipolar devices. Such a technique is provided by the method and apparatus of the present invention as described below.