Abstract:
A thermal sensing system allowing the measurement of the temperature of multiple integrated circuit devices using a single thermal sensor. The thermal sensor is positioned proximally to a first integrated circuit device to obtain ambient temperature readings from the device. The thermal sensor also includes remote sensing capability to measure the temperature of a second integrated circuit device positioned away from the thermal sensor. The thermal sensing system may be used to monitor a microprocessor module for an overheat condition and respond accordingly.

Description:
BACKGROUND INFORMATION 
     Integrated circuit devices comprise many circuit elements arranged compactly in a single physical structure (a “chip”). When operating, these chips tend to generate heat in the course of processing electrical signals. The amount of heat generated by an integrated circuit is dependent on several factors, including the density of circuit elements on the chip, the signal switching speed and the signal power. Chips used in, for example, computers and embedded systems, are likely to generate large amounts of heat, because such integrated circuits generally comprise a very large number of circuit elements arranged on a single chip and are generally operated at high signal switching speeds. Examples of such devices are central processing unit (CPU) chips (such as “microprocessors” or “coprocessors”), memory chips, system control chips (also known as “chipsets”), and others. Excessive heat can degrade performance of these devices, as well as result in permanent physical damage which may cause the chip to fail completely. 
     Microprocessors have been found to be particularly prone to overheating problems, as microprocessors generally comprise the highest densities of circuit elements and are operated at the highest switching speeds. As a result, microprocessors are typically used in conjunction with a “heat sink” or “cooling fan” to help dissipate the heat generated by the chip. Other integrated circuits have likewise been used in conjunction with heat sinks or cooling fans for similar purposes. 
     These heat dissipation steps, however, may not be sufficient to completely counteract the heat generated by the device, particularly as the density of circuit elements in integrated circuits and the speed at which integrated circuits are operated continues to increase. Furthermore, the ambient temperature of the surrounding environment may be such that the cooling measures implemented (such as heat sinks) are inadequate. In such instances, it is desirable to avoid catastrophic failure of the chip by taking more active measures, for example, by placing the device in a low power mode, reducing clock speed or shutting down the device completely. In previous systems, for example, microprocessors have been used in conjunction with thermal monitoring systems that cause certain actions to be taken (e.g., clock “throttling” or shut down) once a critical temperature has been sensed. 
     In the area of, for example, computer design, microprocessor “modules” have been developed that incorporate a microprocessor chip, cache memory chip(s) and system chipset chip(s) on a single printed circuit board. FIG. 1 illustrates a hypothetical arrangement of these components for such a microprocessor module. Printed circuit board  1  includes a microprocessor  2  with heat sink  6 , a system chipset  3  (indicated by the dashed line) and one or more cache chips  4 . The system chipset  3  comprises one or more integrated circuit chips including, for example, a system controller device  7 . A thermal sensor  5  is provided adjacent to microprocessor  2 . In particular, thermal sensor  5  is coupled to electrical ground connections for microprocessor  2 , such that heat generated by microprocessor  2  may be sensed by thermal sensor  5  via an ambient heat sensing capability (see FIG.  2 ). 
     In previous designs, the non-microprocessor chips (the chipset  3  and the cache chips  4 ) were unlikely to experience heat problems. However, as the circuit density and speed of non-microprocessor chips have increased, and as non-microprocessor chips have been located in closer proximity to the microprocessor (particularly as part of a microprocessor module), these non-microprocessor chips have become prone to heat problems in a similar manner as the microprocessor  2 . For example, as shown in FIG. 1, the system controller  7  of chipset  3  may be located in close proximity to microprocessor  2  on the microprocessor module, such that heat generated by microprocessor  2  becomes “coupled” to system controller  7  and contributes to the overall temperature of system controller  7 . 
     Previous responses to similar heat problems in other “thermally critical” devices have been to implement a second thermal sensor proximate to the device. However, the use of an additional thermal sensor in the microprocessor module would not only increase the cost of the module, but also increase the complexity of the design, as multiple thermal sensors must now be controlled and located proximate to the devices to be sensed. Thus, there is a need to monitor the thermal characteristics of multiple integrated circuit chips in a simple and cost effective manner. 
     SUMMARY OF THE INVENTION 
     According to an exemplary embodiment of the present invention, a thermal sensing system is implemented, comprising a first integrated circuit device having a heat sensing element, a second integrated circuit device, and a thermal sensor. The thermal sensor is thermally coupled to the second integrated circuit device to measure the temperature of the second integrated circuit device. The sensor is also electrically coupled to the heat sensing element to measure the temperature of the first integrated circuit device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a top side view of microprocessor module. 
     FIG. 2 shows a cross-sectional view of the microprocessor module of FIG. 1 along the line  2 — 2 . 
     FIG. 3 shows a top side view of an exemplary microprocessor module according to the present invention. 
     FIG. 4 shows a bottom side view of the microprocessor module of FIG. 3, according to the present invention. 
     FIG. 5 shows a cross-sectional view of the microprocessor module of FIG. 4 along the line  5 — 5 , according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     An exemplary embodiment according to the present invention will now be described with reference to FIGS. 3-5, which depict an implementation of an exemplary microprocessor module in conjunction with an exemplary thermal sensing system. According to the present invention, a single thermal sensing device may be employed to detect the thermal characteristics of two integrated circuit devices, and thereby allow a thermal sensing system to provide instruction to counteract an “overheat” condition for one or both devices. The thermal sensing device is positioned to take advantage of its ambient temperature sensing capabilities via thermal coupling, as well as its remote temperature sensing capabilities via electrical connections, to provide temperature measurements of multiple devices. 
     FIG. 3 shows a top side view of an exemplary microprocessor module implementation according to the exemplary embodiment of the present invention. The exemplary embodiment according to the present invention may also be applicable to other circuit configurations; the exemplary microprocessor module described herein provides an example of one possible implementation according to the invention. As shown in FIG. 3, printed circuit board  10  is populated by a microprocessor integrated circuit device  11 , a system chipset  12  (indicated by dashed lines), a number of cache memory chips  13  and a heat sink  14 . System chipset  12  may comprise one or more integrated circuit chips; in the example shown in FIG. 3, system chipset  12  includes a system controller integrated circuit chip  25  and support chips  26 ,  27 . Printed circuit board  10  may also comprise other electronic devices (resistors, capacitors, and so forth) which are not shown. 
     Microprocessor  11 , chipset  12  and cache memory chips  13  may be mounted to printed circuit board  10 , for example, by surface mount connection, or by another well known device mounting method. In the example of FIG. 3, microprocessor  11  and system controller  25  are ball grid array (BOA) type devices that are surface mounted to top side  18  of printed circuit board  10 . Also as shown in FIG. 3, system controller  25  is mounted in close proximity to microprocessor  11 , such that heat generated by microprocessor  11  may be “coupled” to system controller  25 , causing the overall increase in the temperature of system controller  25 . 
     Heat sink  14  may be coupled only to microprocessor  11 , or (as shown in FIG. 3) may be coupled to both microprocessor  11  and system controller  25  in order to increase heat dissipation between the two devices. Heat sink  14  may take any well known form for such heat sinking devices, and thus the actual size and shape of the heat sink  14  used with the exemplary microprocessor module may differ from that depicted in FIG. 3 for illustrative purposes. 
     Exemplary microprocessor  11  contains a heat sensing element  15  internal to microprocessor  11  (illustrated as a cutaway portion in FIG. 3) that provides an indication of the temperature of microprocessor  11 . Microprocessors including such heat sensing elements include the PENTIUM®-ID microprocessors sold by Intel Corporation of Santa Clara, Calif. In the present example, heat sensing element  15  comprises a diode-type element. 
     FIG. 4 shows a view of a bottom side  19  of the printed circuit board  10  for the exemplary microprocessor module of FIG.  3 . The dashed lines shown in FIG. 4 indicate the relative locations of the microprocessor  11 , chipset  12  (including system controller  25 ) and cache chips  13 , which are mounted on the top side  18  of the printed circuit board  10 . Ground vias  16  are located in printed circuit board  10  to allow connection on bottom side  19  to electrical ground interconnections for system controller  25  of chipset  12 , and signal vias  17  are located in printed circuit board  10  to allow electrical connection on bottom side  19  to interconnections for the heat sensing element  15  internal to microprocessor  11 . 
     As shown in FIG. 4, a thermal sensor  20  is mounted on the bottom side  19  of printed circuit board  10 . Thermal sensor  20  includes an “ambient” temperature sensing capability for measuring the temperature of devices through the monitoring of ground connections made to those devices. As shown in FIG. 4, thermal sensor  20  is thermally coupled to the ground vias  16  for the ground interconnections of system controller  25  (for example, by surface mounting using metallic solder compounds). FIG. 5, which shows a cross-sectional view of the microprocessor module, also illustrates the connection of thermal sensor  20  to the electrical ground connections for system controller  25 . 
     Thermal sensor  20  further includes “remote” temperature sensing capability for measuring the temperature of remote devices in conjunction with heat sensing elements. Remote sensing connections  21  of thermal sensor  20  are electrically connected to signal vias  17  in order to electrically couple with the heat sensing element  15  internal to microprocessor  11 . Thermal sensors of this type are sold by, for example, Analog Devices Corp. of Norwood, Mass., and Maxim Corp. of Santa Clara, Calif. 
     Thermal sensor  20  further includes at least one thermal signal output  22 , which is provided to a thermal control system  23  (which may comprise, for example, a microcontroller). Thermal control system  23  may be configured to respond to temperature conditions sensed at one or both of the microprocessor  11  and chipset  12  as indicated by the thermal sensor  20 . For example, the thermal control system  23  may be configured to reduce system clock frequency (clock throttling) in response to a temperature condition that exceeds a threshold temperature, or may be configured to shut down the system completely. 
     It should be noted that the ambient temperature sensing capability for exemplary thermal sensor  20  is more accurate when closely coupled to the ground connection of the device to be measured. Thus, the placement of the thermal sensor  20  on the bottom side  19  of printed circuit board  10  facilitates the accurate temperature measurement of system controller  25 , which, in this example, has its ground interconnections located in the center portion of the device (see FIGS.  4  and  5 ). If the ground interconnections were located on the perimeter of the device, thermal sensor  20  could be located, for example, on the top side  18  of the printed circuit board  10  without excessive loss of measurement accuracy. 
     It should be further noted that the ambient temperature sensing capabilities of thermal sensor  20  can be applied to other devices mounted to printed circuit board  10 , should temperature sensing become more critical for such devices. For example, the thermal sensor  20  may be located proximate to one of the cache memory chips  13  or another of the devices of chipset  12 , if measurement of the temperature of these chips is desired. 
     The exemplary embodiment according to the present invention has been implemented by Intel Corporation, for example, as part of its mobile PENTIUM®-ID microprocessor module. This implementation includes a PENTIUM®-ID microprocessor, a 440BX system control chipset and at least one cache memory device on a single printed circuit board for use, for example, in mobile computing applications (e.g., notebook computers). This implementation also includes a Maxim MAX1617 thermal sensor device for use in both ambient thermal sensing and remote thermal sensing. The exemplary embodiment according to the present invention is useful for mobile computing applications due to the space constraints involved and close proximity of each electronic device. 
     In the preceding specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.