Abstract:
The present invention is related to method and apparatus for on-die noise detection that includes one more voltage noise sensors, and one or more associated comparators. The voltage noise sensor includes a circuit including devices designed to position an initial voltage level of nodes between the devices at certain levels. The nodes are paired where the initial level of one node is above the initial level of the other node in the pair. The devices are designed to position the initial voltage levels of nodes of each pair such that the occurrence of noise above a predefined threshold voltage causes at least one of the voltage levels at the pair of nodes to approach and pass the other. The comparator monitors the voltage levels of each pair of nodes and generates a trigger signal upon detection of the voltage levels at a pair of nodes passing each other.

Description:
BACKGROUND  
         [0001]    1. Field  
           [0002]    This invention relates to noise detection, and more specifically to noise detection in microcircuits.  
           [0003]    2. Background  
           [0004]    In the design of microcircuits, the power delivery system and any associated power supply noise are key factors. Noise can introduce marginal functional problems with the operation of the microcircuit. These problems may only surface if certain patterns or programs are being processed by the microcircuit. Unfortunately, many times noise may not be visible at the input/output (I/O) pins of the microcircuit. Further, probing these pins to detect noise may affect the actual noise measured at the pins. Moreover, if the microcircuit is installed in a system, it may be extremely difficult to probe.  
           [0005]    In some cases, to identify a suspected noise problem, the microcircuit is opened up and the existing die probed using a pico-probe to detect on-die voltage noise. However, on-die differential probing is extremely difficult, productivity is low, and there is no guarantee of getting results.  
           [0006]    Therefore, there is a need for detection of on-die voltage noise in microcircuits that allows easy identification and quantification of potential in-system device power droop/noise problems.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]    The present invention is further described in the detailed description which follows in reference to the noted plurality of drawings by way of non-limiting examples of embodiments of the present invention in which like reference numerals represent similar parts throughout the several views of the drawings and wherein:  
         [0008]    [0008]FIG. 1 is a block diagram of a microcircuit with on-die voltage noise detection according to an example embodiment of the present invention;  
         [0009]    [0009]FIG. 2 is a block diagram of a voltage noise detector cell according to an example embodiment of the present invention;  
         [0010]    [0010]FIG. 3 is a voltage noise detector circuit according to an example embodiment of the present invention;  
         [0011]    FIGS.  4 A-D are graphical illustrations of maximum noise detection according to an example embodiment of the present invention;  
         [0012]    FIGS.  5 A-D are graphical illustrations of minimum noise detection according to an example embodiment of the present invention;  
         [0013]    [0013]FIG. 6 is a block diagram of a microcircuit with multiple voltage noise detection cells according to an example embodiment of the present invention;  
         [0014]    [0014]FIG. 7 is a diagram of an array of voltage noise detection cells according to an example embodiment of the present invention; and  
         [0015]    [0015]FIG. 8 is a block diagram of a system for on-die voltage noise detection according to example embodiment of the present invention.  
     
    
     DESCRIPTION  
       [0016]    The particulars shown herein are by way of example and for purposes of illustrative discussion of the embodiments of the present invention. The description taken with the drawings make it apparent to those skilled in the art how the present invention may be embodied in practice.  
         [0017]    Further, arrangements may be shown in block diagram form in order to avoid obscuring the invention, and also in view of the fact that specifics with respect to implementation of such block diagram arrangements is highly dependent upon the platform within which the present invention is to be implemented, i.e., specifics should be well within purview of one skilled in the art. Where specific details (e.g., circuits, flowcharts) are set forth in order to describe example embodiments of the invention, it should be apparent to one skilled in the art that the invention can be practiced without these specific details. Finally, it should be apparent that any combination of hard-wired circuitry and software instructions can be used to implement embodiments of the present invention, i.e., the present invention is not limited to any specific combination of hardware circuitry and software instructions.  
         [0018]    Although example embodiments of the present invention may be described using an example system block diagram in an example host unit environment, practice of the invention is not limited thereto, i.e., the invention may be able to be practiced with other types of systems, and in other types of environments.  
         [0019]    Reference in the specification to “one embodiment” or “an embodiment” means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in one embodiment” in various places in the specification are not necessarily all referring to the same embodiment.  
         [0020]    [0020]FIG. 1 shows a block diagram of a microcircuit with on-die voltage noise detection according to an example embodiment of the present invention. Microcircuit  10  may include one or more voltage noise sensors  12  connected to one or more comparators  16 . A voltage noise sensor  12  and a comparator  16  make up a voltage noise detector cell (VND). Noise sensor  12  may monitor the power supply (Vcc) voltage level and the ground (Vss) voltage level to detect differences or changes between the two levels. Voltage noise sensor  12  may detect a maximum noise level (overshoot) and a minimum noise level (undershoot), and relay information regarding this via signal lines  14  to comparator  16 . Comparator  16  compares the signals  14  received from voltage noise senor  12  and determines if noise detected has exceeded a predetermined threshold and if so, a triggering signal  18  may be generated by comparator  16 .  
         [0021]    Since the voltage noise sensor  12  and comparator  16  are on a die of microcircuit  10 , a separate quiet analog power supply to provide a reference is not required. Further, a VND or array of VNDs according to the present invention may be easily dropped into a microcircuit design for late stage product implementations. No special custom routing and placement requirements are needed. Further, a VND/comparator design according to the present invention may be process dependent instead of product dependent, therefore the present invention may be a component in the standard library of a process for any product to use.  
         [0022]    [0022]FIG. 2 shows a block diagram of a voltage noise detector cell according to an example embodiment of the present invention. This cell may be connected between power source  50  and a ground source  52  of a microcircuit directly as shown in FIG. 2, or through optional transistors. The optional transistors may connect node  50  to VCC or node  52  to VSS. These optional transistors, when switched off, may prevent current flow through voltage noise sensor  12 , to reduce power. Transistors or switching devices  20 ,  22 ,  24  and  26  may be connected between power source  50  and another transistor or switching device  28 ,  30 ,  32  and  34 . The transistor/switching devices  28 ,  30 ,  32  and  34  may be connected to the ground source  52 . Devices  20  and  22  may be identical and may be interconnected. Similarly, devices  24  and  26  may be identical and connected, devices  28  and  30  may be identical and connected, and devices  32  and  34  may also be identical and inter-connected.  
         [0023]    A node  40  (Vssup) may be defined between the connection of devices  20  and  28 . Similarly, a node  42  (Vccup) may be defined between the connection of devices  22  and  30 , a node  44  (Vssdn) may be defined between the connection of devices  24  and  32  and a node  46  (Vccdn) may be defined between the connection of devices  26  and  34 . Devices  20 ,  22 ,  24  and  26  may be a different type device than devices  28 ,  30 ,  32  and  34 . For example, devices  20 ,  22 ,  24  and  26  may be PMOS type devices, whereas devices  28 ,  30 ,  32  and  34  may be NMOS type devices. The transistor/switching devices  20 ,  22 ,  24 ,  26 ,  28 ,  30 ,  32  and  34  may be biased in deep saturation region, therefore, the current may be independent of power level.  
         [0024]    The node  40  (Vssup) may connect to the gates of devices  28  and  30 , and node  42  (Vccup) may connect to the gates of devices  20  and  22 . Similarly, node  44  (Vssdn) may connect to the gates of devices  32  and  34 , and node  46  (Vccdn) may connect to the gates of devices  24  and  26 .  
         [0025]    The voltage noise detector cell may be designed such that nodes Vccdn  46  and Vccup  40  follow the movement of the power source voltage level  50 . Further, the node Vssup  42  and node Vssdn  44  may follow the movement of the ground voltage level  52 . By following the movement of the power (Vcc) and the ground (Vss), the current of the voltage noise sensor may be maintained at a constant level.  
         [0026]    An apparatus for detection of on-die voltage noise according to the present invention may be designed with device sizes and interconnections between the devices such that the voltage level at the Vssup node  40 , Vccup node  42 , Vssdn node  44 , and Vccdn node  46  are at certain levels relative to another. Specifically, a VND cell may be designed such that the voltage level of the Vccup node  40  is below the voltage level of the Vssdn node  42 . Thus, when positive noise is detected (Vcc−Vss), the voltage level of the Vccup node  42  goes above that of the voltage level at the Vssdn node  44 , thereby causing the comparator to generate a trigger. Similarly, the VND cell may be designed so the voltage level of the Vssup node  40  is below the voltage level of the Vccdn node  46 . Therefore, when negative noise is detected (Vcc−Vss) the voltage level at the Vccdn node  46  goes below that of the voltage level at Vssup node  40 , thus causing the comparator to generate a trigger. Therefore, according to the present invention, a voltage noise detector cell may detect a maximum overshoot noise and a minimum undershoot noise.  
         [0027]    A voltage noise detector cell according to the present invention may be disabled when noise detection is not desired, thus saving power, and enabled when noise detection is desired. Further, the voltage noise detection cell is not sensitive to process, voltage, or temperature variations and does not measure direct current (DC) voltage differential. Thus the Vccup node  42  and the Vssdn node  44  may be used for maximum (Vcc−Vss) node noise detection, and the Vccdn node  46  and the Vssup node  40  used for minimum (Vcc−Vss) noise detection.  
         [0028]    Moreover, although eight transistors/switching devices are used in this example embodiment, the present invention is not limited by this number of devices, and any number of devices may be used, less than or more than eight, and still be within the spirit and scope of the present invention. Further, although four nodes have been defined in this example embodiment, the present invention is not limited by the use of four nodes and any number of nodes may be defined to implement the present invention.  
         [0029]    [0029]FIG. 3 shows a voltage noise detector circuit according to an example embodiment of the present invention. In this example embodiment, a voltage noise sensor is composed of eight transistor devices where four transistor devices are PMOS devices and four transistor devices are NMOS devices. The transistor devices may be specifically sized to obtain specific voltage levels at the Vssup node, Vccup node, Vssdn node, and Vccdn node based on the desired noise threshold to be detected by this voltage noise detector cell. The top left two transistor devices may be identical, the top right two transistor devices may be identical, the bottom left two transistor devices may be identical and the two bottom right transistor devices may be identical.  
         [0030]    An input enable signal  140  may be used to enable the voltage noise detector. An input search signal  142  may enable a latch inside the comparator to lock the detection signal. This voltage noise detector cell may be used to accurately capture overshoot and undershoot noise, and has no input or reference. An os1 us0 signal  144  may be used for controlling which detection result is output. For example, when the os1us1 signal is at a high level, an overshoot detection result may be sent out, whereas when the os1us1 signal is at a low level, an undershoot detection result may be sent out. According to the present invention, overshoot and undershoot noises may be detected at the same time. In this example embodiment, two comparators  150 ,  160  are used, one for overshoot detection  150  and one for undershoot detection  160 . A multiplexer  170  may be used to select between passing the overshoot detection result os# or the undershoot detection result us# to the trigger output signal  180 .  
         [0031]    The comparator may be shared by multiple voltage noise sensors with proper design changes. Moreover, each voltage noise detector cell may be modified or designed to be able to support multiple noise threshold level detection.  
         [0032]    FIGS.  4 A-D show graphical illustrations of maximum noise detection according to an example embodiment of the present invention. FIG. 4A shows a graph of a 20 mv. peak-to-peak noise sine wave added to Vcc at 1.1 volt. FIG. 4B shows a 20mv. peak-to-peak noise sine wave added to Vss at 0 volts. In this example embodiment, the noise on Vcc and Vss are 1800 out of phase. The top graph in FIG. 4C shows the voltage at the Vssdn node, and the bottom graph in FIG. 4C shows the voltage level at the Vccup node. FIG. 4C illustrates how the voltage level movements at the Vccup node are dominated by voltage level changes in Vcc, and how the voltage level movements at the Vssdn node is dominated by voltage level changes of Vss. When the voltage level of the Vccup node goes above the voltage level of the Vssdn node, this signifies that the voltage noise threshold level that the voltage noise detection cell was designed for has been reached. The points where the voltage level of Vssdn and the voltage level of Vccup overlap are where the voltage noise threshold has been reached or exceeded. A comparator monitors these voltage levels at the Vssdn and Vccup nodes and when overlap is detected, the comparator to generates a trigger, shown in FIG. 4D. A trigger being generated by the comparator signifies that noise has been detected at or above the threshold that the voltage noise detection cell was designed to detect. Therefore, by inserting different amounts of voltage differential between the Vssdn node and the Vccup node, the voltage noise detection cell triggers at different amounts of positive (Vcc−Vss) noise accordingly, in this case, +20 mv.  
         [0033]    FIGS.  5 A-D show graphical illustrations of minimum noise detection according to an example embodiment of the present invention. FIG. 5A shows a graph of a 160 mv. peak-to-peak noise sine wave added to Vcc at 1.05 volts.  
         [0034]    [0034]FIG. 5B shows a graph of a 160 mv. peak-to-peak sine wave added to Vss at 0 volts. In this example embodiment, the noise on Vcc and Vss are 1800 out of phase. In FIG. 5C, the top graph shows the voltage level at the Vssup node and the bottom graph shows the voltage level at the Vccdn node. FIG. 5C illustrates how the voltage level at the Vccdn node follows changes in the voltage level of Vcc, and how the voltage level at the Vssup node follows changes in the voltage level of Vss. A comparator monitors the voltage levels at the Vccdn node and the Vssup node, and when the voltage level at the Vccdn node goes below the voltage level at the Vssup node, the comparator generates a trigger as shown in FIG. 5D. Therefore, according to the present invention, by inserting different amounts of voltage differential between the Vssup node and the Vccdn node, a voltage noise detection cell may trigger at different amounts of negative (Vcc−Vss) noise, in this case, −160 mv.  
         [0035]    [0035]FIG. 6 shows a block diagram of a microcircuit with multiple voltage noise detection cells according to an example embodiment of the present invention. A microcircuit  110  according to the present invention may include an array of voltage level noise detection cells  60 ,  70 ,  80  and  90  interconnected to multiple comparators  62 ,  72 ,  82  and  92 , respectively. Each voltage noise detector cell may be designed to detect the occurrence of voltage noise at or above a specific threshold level. For example, the voltage noise detector cell  60  may be designed to detect any noise above 200 mv, the voltage noise detector cell  70  designed to detect any noise above 220 mv, the voltage noise detector cell  80  designed to detect any noise above 240 mv and the voltage noise detector cell  90  designed to detect any noise above 260 mv. Each voltage noise detector noise cell  60 ,  70 ,  80  and  90  may be individually enabled by setting a bit in a register  68 ,  78 ,  88  and  98 , respectively. These enable registers  68 ,  78 ,  88  and  98  may be controlled or written to by devices external to microcircuit  110  thereby allowing the enabling of voltage noise detection of either 200 mv, 220 mv, 240 mv, 260 mv or a combination thereof. The enable signals  66 ,  76 ,  86 ,  96  are sent from registers  68 ,  78 ,  88  and  98  to the individual voltage noise detection cells  60 ,  70 ,  80  and  90 , respectively. The enable signals  66 ,  76 ,  86 ,  96  may also be the same enable signal.  
         [0036]    Each comparator  62 ,  72 ,  82  and  92  may send any generated trigger signal  64 ,  74 ,  84  and  94 , respectively, to a register to be stored. Therefore, if voltage noise is detected above 200 mv, a trigger  64  may be generated by comparator  62  and stored in register  106 . Similarly, a trigger  74  generated by comparator  72  for noise detected above 220 mv may be stored in register  104 , a trigger  84  generated by comparator  82  for noise detected above 240 mv may be stored in register  102 , and a trigger  94  generated by comparator  92  for noise detected above 260 mv may be stored in register  100 .  
         [0037]    The registers  100 ,  102 ,  104  and  106  that store the triggers may be accessible external to microcircuit  110 , thereby allowing reading of any detected voltage level noise at the various threshold levels. Further, each noise detector cell may be disabled, and the registers  100 ,  102 ,  104 ,  106  reset to allow a new monitoring and new detection of voltage level noise. Although an array of four voltage noise detector cell combinations are shown in this example embodiment, the present invention is not limited by this number and less or more voltage noise detection cells may be used to implement the present invention. Further, each voltage noise detection cell may be located in the same area or different areas of microcircuit  110  thereby allowing voltage noise detection throughout the circuitry on microcircuit  110 .  
         [0038]    [0038]FIG. 7 shows a diagram of an array of voltage noise detection cells according to an example embodiment of the present invention. In this figure, blocks  200 - 214  are shown representing an array of eight voltage noise detection cells (VNDs). A delay circuit  216  may also be connected to the array of voltage noise detection cells and used to generate a search signal from an enable signal, discussed previously regarding FIG. 3. The amount of delay may be set to insure that the noise sensors are fully initialized, before the detection signal is latched, to avoid false trigger.  
         [0039]    Each voltage noise detection cell  200 - 214  produces a trigger output signal  220 - 234 , respectively, when that VND detects voltage noise above the threshold level that the VND was designed for. The trigger output signal  220 - 234  may be designed to be either a pulse (as shown in the example embodiments of FIGS. 4D and 5D), or to be an active edge trigger latched and maintained signal. The trigger output signals  220 - 234  may be used as inputs to counters to allow the recording of the number of each VND trigger within a time period. This allows an on-die noise histogram to be obtained for circuit activities and software induced noise analysis.  
         [0040]    This array of voltage noise detection cells with trigger points tuned at different noise levels may be dropped into or implemented in any die to allow voltage droop detection. An array of voltage noise detection cells (or individual voltage noise detection cells) may be placed on the same die of a microcircuit at different locations. This allows a noise profile or map of the die to be obtained. This information may be very useful for circuit power noise decoupling design. In this example embodiment, the array of voltage noise detection cells may be designed to detect, for example, voltage overshoot of 20 mv to 160 mv, and voltage undershoot of 60 mv to 180 mv.  
         [0041]    [0041]FIG. 8 shows a block diagram of a system for on-die voltage noise detection according to example embodiment of the present invention. One or more microcircuits  122 ,  126  and  130  may be interconnected in a system with other logic circuits and/or devices  134 ,  136 . Each microcircuit  122 ,  126 ,  130  may include on-die voltage noise detection logic  124 ,  128  and  132 , respectively. Another device  120  in the system may be used to enable voltage noise detection logic  124 ,  128  and  132  thereby allowing monitoring and detection of voltage level noise on each of microcircuits  122 ,  126 ,  132 , respectively. The device  120  may be a controller, a processor, a tester, or a debugger type device used for the purpose of noise monitoring, or handling the monitoring of noise on microcircuits as one of its tasks or functions in the system. Therefore, voltage level noise may be monitored and detected in real-time on each of microcircuits  122 ,  126  and  130  without the microcircuit being probed, or disconnected from the system. Further, this allows voltage level noise to be monitored and detected during real operation of the microcircuits  122 ,  126  and  130 , as well as specific patterns or applications run to determine their effect on voltage level noise in each of the microcircuits. Microcircuits  122 ,  126  and  130  may also be different circuits or functional blocks on the same die. Moreover, microcircuits  122 ,  126  and  130  may have different power sources.  
         [0042]    Apparatus for detection of on-die voltage noise in microcircuits is advantageous for a number of reasons. For example, the present invention solves the problem of the current inability to micro-probe/pico-probe in-system product on die (Vcc−Vss) differentials to form the on die AC (alternating current) voltage noise profile for in-system product power delivery design verification. The present invention solves the current problem of the inability to verify device voltage stress distribution in various systems for detailed reliability risk assessment; resulting in poor optimization between product reliability risks and performance. Further, the current problem of inability to correlate performances, such as speed paths and clock jitters, to the magnitudes of global and localize voltage noise is solved, as well as the problem of the current inability to verify the effectiveness of various di/dt vector programs, such as the worst SSO vectors, to accelerate product validation.  
         [0043]    Moreover, apparatus for detection of on-die voltage noise in microcircuits is advantageous in that the present invention is highly accurate and it&#39;s performance is independent of process, voltage, or temperature, to avoid tedious calibrations and the use of fuse cells. Further, apparatus for detection of on-die voltage noise and microcircuits according to the present invention have wide frequency range and are capable of catching high frequency AC noise at the core clock frequency range. Moreover, the present invention may be easily dropped in to a die for late stage product implementation, and does not require a separate quiet analog power supply to provide a reference. Further, the present invention requires no special custom routing or placement. The present invention may be a self-contained circuit that can be dropped in any vacancy without additional layout effort. The design of circuitry according to the present invention is process dependent instead of product dependent. Therefore, it may be a component in a standard library of a process for any product to use. Additionally, although the present invention has been illustrated as being on-die of a microcircuit, voltage noise detection using the present invention may be applied to devices and circuitry that are not on a die of a device.  
         [0044]    It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to a preferred embodiment, it is understood that the words that have been used herein are words of description and illustration, rather than words of limitation. Changes may be made within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular methods, materials, and embodiments, the present invention is not intended to be limited to the particulars disclosed herein, rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.