Decoupling capacitors for integrated circuits

On-chip decoupling capacitors and methods for placing the same are disclosed in which designated spaces are created between the active circuits to insert designated capacitor cells. The designated capacitor cells may be placed in designated areas of the integrated circuit that are not simply spaces left empty by cell placement or frontier areas in or around the route, and the dimensions (e.g., height) of the designated capacitor cells may be selected to optimize (increase) capacitance efficiency. The capacitor cells may also be placed to target and reduce the interference between a digital core (aggressor) circuit and a victim analog circuit.

FIELD OF THE INVENTION

This disclosure generally relates to integrated circuits, and more particularly to placement of decoupling capacitors for integrated circuits.

BACKGROUND OF THE INVENTION

De-coupling capacitors have been employed for integrated circuits to reduce transient voltage and currents, and to manage loop currents and digital supply ripple that occur during integrated circuit chip operation. On-chip decoupling capacitors have been placed in the unused boundary areas of an integrated circuit, outside the active circuitry (outside the digital core) of the integrated circuit, in the spaces left empty by cell placement or frontier areas in or around the route. In the past, the amount of decoupling capacitors needed in the digital route to manage loop currents and digital supply ripple has defined the final digital cores size in spur-sensitive integrated circuits. This is mainly due to the low efficiency of the available decoupling cells and the need to have considerable in-route capacitance. This causes the maximum digital route utilization to be determined not by the routability of the core but by the amount of in-route cap needed.

SUMMARY OF THE INVENTION

Disclosed herein are integrated circuits that employ on-chip decoupling capacitors and methods for placing the same in which designated spaces are created between the active circuits to insert designated capacitor cells. In one embodiment, such designated capacitor cells may be placed in designated areas within the digital core of an integrated circuit that are not simply spaces left empty by cell placement or frontier areas in or around the route. In another embodiment, the dimensions (e.g., height) of the designated capacitor cells may be selected to optimize (increase) capacitance efficiency. In yet another embodiment, the placement of the capacitor cells may be selected to target and reduce the interference between a digital core (aggressor) circuit and an analog circuit (victim). In this regard, capacitor cells may be placed so as to increase the quantity of decoupling capacitance per area in the digital route and to optimize its placement so as to reduce the coupling from the digital circuits to the analog circuits in an integrated circuit, e.g., by placing decoupling capacitors adjacent or otherwise near to current perturbation source/s so as to reduce the size and effects of current loops.

In one exemplary configuration, designated capacitor cells may be rows (and/or columns) that are placed to specifically target the interference between digital core (aggressor) circuitry and an analog circuit (victim), and not based on fan-out or signal integrity concerns. In another exemplary configuration, one or more decoupling capacitors may be formed to substantially fully occupy the space across a cell row, e.g., such as across a cell row defined by a single MOS-type cell (PMOS or NMOS) between power supply rails. In yet another exemplary embodiment, designated capacitor cells may be placed in areas within the outer boundary of a digital core so as to minimize of or substantially eliminate current loop and other coupling interference imparted to analog circuitry that is placed to at least partially surround the outer boundary of the digital core.

The disclosed circuits may be implemented using a cell topology and placement strategy that may employ one or more of the following features. First, utilization may be forced to be as high as possible while still allowing the core to be routed. If desired, common decoupling cells may be still used where possible as fillers. Second, a single MOS-type cell (PMOS or NMOS) may be created, and the dimensions of the transistor/s in this cell may be configured to increase area efficiency of a decoupling cell subject to the quality factor needed for each specific application. In this regard, area efficiency of a decoupling cell may be defined as: (capacitor area/total cell area)×100.

Well/substrate biasing considerations and non-obstructing layout may also be considered. In one exemplary embodiment, this approach may be employed to enable the area efficiency of the single cell to be greater than 30% and in one embodiment to be as high as about 80%. This is in contrast to conventional cell rows that are used to create common CMOS decoupling capacitor cells containing both nWells and pWells, and which have an area efficiency as low as 15% or less. In this regard, such a conventional CMOS common cell needs to contain both nWell and pWell so that it can be abutted to the adjacent standard cells without further waste of space. The existence of the two wells forces the decoupling capacitors to be both NOMS and PMOS. This type of decoupling cell is limited by several spacing design rules (e.g., such as Implant over Active area overlap; nWell overlap of P+ Active area and Space to N+ Active Area; and Poly space to Active area) which forces considerable space to be wasted in the distance between structures. More particularly, the tallest common capacitor decoupling cells typically have a highest area efficiency of 30%, although such taller cells often cannot be used in the layout of conventional decoupling capacitor approaches. Smaller height conventional cells typically have an area efficiency of 15% or less.

In one embodiment, the height of a single MOS-type decoupling cell row may be configured to be an even multiple of the standard cell row height in order to allow capacitors of the decoupling cell row to easily connect to the same supply rail (positive or negative) on both sides of the decoupling cell row. In such a case, this configuration allows direct biasing of the single well in the cell and makes the interface to the upper and lower rows of cells direct, e.g., with substantially no waste of space. The access to the supply of polarity opposite to the polarity that biases the well may be accomplished in one exemplary embodiment by directly tapping a supply mesh constructed over the circuit. Third, decoupling capacitors may be placed in rows that occupy the full height of the placement and routing core, e.g., such that substantially no space is wasted to meet minimum distance design rules to wells in horizontally-adjacent standard cells. Further, multiple decoupling capacitor cells in the same decoupling cell row may be tiled side by side so as to all have the same height.

In one embodiment of the disclosed circuits and methods, decoupling cell rows may be configured to be equidistant in a digital circuit core with homogeneous/balanced power consumption, or the distance between decoupling cell rows may be chosen (e.g., varied) according to the spatial current distribution in order to reduce both the area of higher-current loops and the local supply ripple. The decoupling cell rows may also be configured in a way that takes into account the frequency components of interest in the supply current as well as the distance to the victim circuit.

The following hypothetical example illustrates how integrated circuit routing and capacitor efficiency may be optimized using the disclosed circuits and placement methods. A conventional integrated circuit design which originally required utilization to be restricted to 80% to provide a given amount of capacitance using common CMOS decoupling cells with 24.5% efficiency, may be re-implemented in one exemplary embodiment to achieve a routability-limited utilization of about 92%, with excess circuit area being occupied by rows of high-efficiency single MOS-type decoupling cells. In this regard, if all of the excess circuit area is retained, the total decoupling capacitance may be further increased by a factor of about 2.35. Alternatively, most of the excess circuit area may be removed from a given integrated circuit, and a smaller amount of high-efficiency single MOS-type decoupling cells and associated circuit area may be employed than is required using conventional CMOS capacitor and placement methodology while at the same time providing the a substantially equivalent amount of capacitance, thus reducing the cost of the integrated circuit.

In one respect, disclosed is an integrated circuit device, including: a silicon substrate; analog circuitry formed on the silicon substrate; a digital core formed on the silicon substrate separate from the analog circuitry, the digital core including at least one area of active digital circuitry; one or more decoupling cell rows formed on the substrate within the area of active digital circuitry, each of the given decoupling cell rows including at least one p-type doped well or a n-type doped well extending across an entire height of the decoupling cell row; and one or more metal-oxide-semiconductor (MOS) decoupling capacitors formed within the at least one p-type doped well or n-type doped well of each of the decoupling cell rows.

In another respect, disclosed herein is a method for configuring an integrated circuit device, including: providing a silicon substrate; forming analog circuitry on the silicon substrate; forming a digital core on the silicon substrate separate from the analog circuitry, the digital core including at least one area of active digital circuitry; forming one or more decoupling cell rows on the substrate within the area of active digital circuitry, each of the given decoupling cell rows including only one of a p-type doped well or a n-type doped well extending across an entire height of the decoupling cell row; and forming one or more metal-oxide-semiconductor (MOS) decoupling capacitors in the p-type doped well or n-type doped well of each of the decoupling cell rows.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1Aillustrates an overhead view of a portion of an integrated circuit (IC)100configured according to one exemplary embodiment. In this embodiment, IC circuit100may be a silicon substrate having standard complementary metal-oxide-semiconductor (CMOS) cell rows102and a NMOS decoupling row110defined thereon between a pair of standard cell rows102. As illustrated inFIG. 1A, a decoupling row110may be configured to have a height (i.e. the vertical distance inFIG. 1Abetween the adjacent supply rails152on either side of decoupling row110) that is substantially twice the height of the standard cell rows102(i.e. the vertical distance inFIG. 1Abetween the adjacent supply rails152and154on either side of each standard cell row110), although a decoupling row110may alternatively be configured to have a height that is greater than twice the height of standard cell rows102or less than twice the height of standard cell rows102. Separating and delineating the standard cell rows102and decoupling row110are positive supply rails154and negative supply rails152that may be overlying parallel-oriented metallization layers that supply power using interconnects (e.g., vias) to the underlying active circuitry of IC100. The underlying active circuitry may be defined underneath and between the adjacent overlying supply rails.

In the exemplary embodiment ofFIG. 1A, standard cell rows102may be used to form circuitry of digital logic rows290of IC200ofFIG. 2, although it is alternatively possible that a decoupling row110may be provided between standard cell rows102that are empty and/or that are used to form decoupling capacitors. It is also possible that a decoupling row110may be defined adjacent the edge of digital circuitry, i.e., digital logic rows290on one side and empty standard cell rows102on the other side. InFIG. 1A, the illustrated lines180represent frontier areas between individual standard logic cells184in standard cell rows102, and the illustrated lines182represent frontier areas between individual decoupling capacitor cells186in decoupling row110. As shown, the width of individual standard logic cells184(i.e., the horizontal distance inFIG. 1Abetween adjacent frontier area lines180) may vary in this embodiment due to circuitry design, whereas all of the individual decoupling capacitor cells186may be configured to have the same standardized width (i.e., the horizontal distance inFIG. 1Abetween adjacent frontier area lines182) which may be, for example, the largest cell width (or transistor size) that results in a satisfactory capacitor quality factor for the decoupling capacitors. As shown, decoupling capacitor cells186of this optimized width may be disposed as tiles of substantially the same size across the width of decoupling row110, although it may sometimes be desirable to place narrower decoupling cells at the opposing terminal ends of a decoupling row110.

As further shown inFIG. 1A, each of standard CMOS cell rows102is defined between a positive supply rail154and an adjacent corresponding negative supply rail152having a given standard spacing, and a designated NMOS decoupling row110is defined between two adjacent negative supply rails152having a spacing that is taller than this given standard spacing. In one exemplary embodiment, the taller supply rail spacing of a decoupling row110may be selected to be an even multiple (e.g., 2×, 4×, 6×, etc.) of the narrower spacing of the standard cell rows102such that the decoupling row110may be will be defined between supply rails of like polarity (negative or positive) for coupling on opposing sides of the decoupling row110when it is fit into a pattern of standard cell rows102as shown. As an example, in one exemplary embodiment, the standard spacing height between supply rails152and154of each standard cell row102may be about 1.8 μm, and the taller spacing height between adjacent negative supply rails152of decoupling cell row110may be about 10.8 μm (or 6× spacing), although other greater and lesser heights and spacings may be alternatively employed.

Underlying the power supply rails152and154are respective alternating and parallel-oriented pWell row regions106a,106b(silicon substrate doped with P-type dopant such as Boron) and nWell row regions104(silicon substrate doped with N-type dopant material such as Phosphorous, Arsenic or Antimony) that are formed in CMOS fashion in the substrate of IC100in a manner that coincides with the overlying supply rails152and154. In this regard, each standard CMOS cell row102includes a portion of a pWell region106a,106band a portion of an adjacent nWell region104, with a negative supply rail152overlying each pWell region106a,106band a positive supply rail154overlying each nWell region104. Also as shown, within the standard cell rows102MOS devices formed in each nWell region104are separated from each pWell region by a spacing105, for example, a spacing defined according to spacing rules that require that p+ transistors have a certain minimum enclosure by nWell and that adjacent n+ transistors have a certain minimum spacing from the adjacent abutting nWell. It will be understood that these requirements vary depending on the rules dictated by particular process requirements

FIG. 1Aalso shows NMOS decoupling row110that is defined to include a single pWell region106bthat is taller than the adjacent nWell regions104and pWell regions106aof the standard CMOS cells102. As shown, the taller pWell region106bof decoupling row110may be configured with a height that is sufficient to extend beyond the negative supply rails152that mark the outer boundary of the decoupling row110so as to also fatal a part of the adjacent standard cell rows102formed on either side of decoupling row110. In this regard, height of each pWell region106amay vary in corresponding fashion with height of a given decoupling row110. It will be understood that the illustrated polarity ofFIG. 1Ais exemplary only, and that a decoupling row for an IC may be laid out with a reversed polarity but in otherwise similar fashion toFIG. 1A, i.e., a decoupling row110may be alternatively formed as a PMOS decoupling row that includes a single wide nWell region that is taller than alternating adjacent pWell regions and nWell regions of the standard CMOS cell rows102that surround the decoupling row110.

FIG. 2illustrates an overhead view of an IC200configured according to one exemplary embodiment, showing a breakdown of the digital core208and decoupling rows110defined therein. In this embodiment, IC200includes digital logic active circuitry areas206,209and210within the outer boundary of digital core208, analog circuitry areas202and204at least partially surrounding the outer boundary of digital core208, digital supply regulator circuitry214, and input/output (I/O) PAD circuit areas212that are in this case located at the frontier or edge of the digital circuitry areas209and210outside the outer boundary of the digital core208of IC200. As shown, the circuitry areas of IC200may be optionally laid out in order to increase (e.g., maximize) the distance between noisier circuitry (aggressor circuitry) and noise sensitive circuitry (victim circuitry). In the specific example ofFIG. 2, noise-sensitive analog circuitry202is placed near one corner of IC200and high noise digital circuitry210and digital supply regulator circuitry214are placed near an opposing corner of IC200, with other analog circuitry204, quiet digital circuitry206and intermediate noise digital circuitry209placed therebetween such that the quietest circuitry areas are placed nearest the most noise sensitive circuitry as shown.

Following are example types of circuitry areas that may be present in an IC embodiment such as illustratedFIG. 2, it being understood that other examples of such analog and/or digital circuitry may be present in an IC, and/or that other combinations of analog and/or digital circuitry may be present in an IC. Noise-sensitive analog circuitry202may be, for example, RF frontend circuitry containing as an example low noise amplifier (LNA) and mixer circuitry. Other analog circuitry204may be, for example, Analog—intermediate frequency (IF) circuitry, digital to analog conversion circuitry (DACs), and/or analog to digital conversion circuitry (ADCs). Quiet digital circuitry206may be, for example, circuitry used only when the noise level is not critical, e.g., as when the IC200is powering up, e.g., non-volatile memory (NVM) and part, of read-only memory (ROM). High noise digital circuitry210may be, for example, digital signal processor (DSP) logic with high signal dependent content. It will also be understood that absolute noise level is only one factor that may be considered when determining relative placement and noise type of different types of analog and digital circuitry. For example, RF frontend circuitry may be considered more sensitive because it operates with a lower signal level then the reminder of the circuitry chain, but frequency content may also be considered when determining placement of each type of circuitry. Thus, circuitry210may be categorized as “high noise digital” not only due to its operating signal level, but also because the perturbation it creates is in a frequency band that will disturb the sensible analog circuitry202. In this regard, the frequency band of interest will depend on the individual application.

As further shown inFIG. 2, decoupling rows110are placed within at least a portion of the digital core208of IC200, and specifically within digital circuitry areas209and210between active circuitry formed in standard cell rows102(not shown inFIG. 2) in order to reduce and/or substantially eliminate noise interference caused by the digital circuitry areas209and210. It will be understood that the particular spacing between adjacent decoupling rows110may be selected and/or varied to fit the particular noise or current density characteristics of the active digital circuitry within digital core208, and/or the amount of noise suppression that is desired for a given application. For example, decoupling rows110may be evenly spaced in those areas where current density across the digital core is substantially homogeneous, or decoupling row spacing may vary across the digital core208to correspond to changing current densities across the digital core208, e.g. adjacent decoupling rows110may be spaced closer together in those areas of the digital core208having relatively higher current density and decoupling rows110may be spaced farther apart in those areas of the digital core208having relatively lower current density. Although no decoupling rows110are shown present within quiet digital circuitry206ofFIG. 2, it is alternatively possible that decoupling rows110may also be provided within digital circuitry206or alternatively only within high noise digital circuitry210. In this regard, the disclosed circuitry and methods allow placement of decoupling rows for location of decoupling capacitance in any one or more areas of an IC where needed or desired to fit the noise and layout characteristics of a given application.

Following is an example of the relative surface area of decoupling capacitance that may be provided in one exemplary embodiment within digital circuitry of IC200: digital circuitry areas206,209and210may occupy a combined surface area of 1.86 mm2out of a total surface area of 4.58 mm2for IC200, while decoupling rows110(each row110containing decoupling capacitors) may occupy a combined surface area of 0.19 mm2out of the total surface area of IC200. It will be understood that these relative surface area values are exemplary only, and that they may vary to fit the characteristics of a given application. Moreover, it will be understood that the layout and particular combination of types of circuitry areas ofFIG. 2are exemplary only, and that layout and types of circuitry areas within a particular IC may vary. Moreover, the relative positioning of decoupling rows within circuitry may vary as needed or desired to fit the noise characteristics of the circuitry of a particular IC. Further, although not illustrated inFIG. 2, it will be understood that additional decoupling capacitance may be provided in the form of decoupling rows110and/or standard cell rows102located in edge areas212. In one exemplary embodiment, lower area efficiency conventional decoupling capacitor cells (i.e., common CMOS decoupling capacitor cells containing both nWells and pWells) may be employed inside the standard cell rows102as spacers only in order to minimize the amount of area used by these relatively lower area efficiency capacitor cells by increasing the utilization.

FIG. 2illustrates one exemplary embodiment in which multiple decoupling rows110are formed within the digital core208of an IC200between adjacent standard CMOS cell rows102(which include active digital circuitry) of core208. Although such a multiple row configuration may be employed to maximize area efficiency, it will be understood that decoupling capacitors may be alternatively formed in a grid configuration within digital logic circuitry of a digital core. For example, if a specific digital circuitry region within a digital core208is found to have a noise level that requires a higher decoupling capacitive density than is achievable using a geometry of multiple decoupling rows110such as illustrated inFIG. 2, then a grid approach having decoupling capacitor cells arranged in columns that are oriented in perpendicular relationship to the standard cell rows may additionally or alternatively be used. For example, in one such alternative embodiment illustrated inFIG. 1B, each of the decoupling capacitor cell columns111may intersect the decoupling capacitor cell rows110to form a grid of intersecting decoupling capacitor cell rows110and decoupling capacitor cell columns111, with the decoupling capacitor cell columns111being formed using the same single type well (e.g., single pWell or nWell) extending across the height of each of the decoupling columns111in a manner similar to the way in which a single type well extends across the height of the intersecting decoupling capacitor rows110.

For example, a decoupling capacitor cell column111may be formed from multiple relatively narrow width decoupling capacitor cell rows that are stacked in abutting relationship to each other and that also abut the wider decoupling capacitor cell row/s110as shown inFIG. 1B. As shown, such narrow decoupling capacitor cell rows of a decoupling capacitor cell column111may be formed to bisect standard cell rows102in areas between the wider decoupling capacitor cell rows110. In this regard, the pair of three dots illustrated inFIG. 1Bare present to show that the pattern of integrated circuit (IC)100may extend such that the pWell of a given decoupling capacitor cell column111may extend in opposite upward and downward vertical directions (relative to the page) to form a column of continuous pWell areas that are oriented in perpendicular relationship to the orientation of both the standard cell rows102and decoupling capacitor cell row/s110. In one embodiment, such a decoupling capacitor cell column may extend between and intersect adjacent decoupling cell rows110. It will be understood that as with decoupling cell rows110, a decoupling capacitor cell column111may be alternatively formed using nWell areas in other embodiments having different polarity.

In one embodiment, an individual segment of a capacitor cell column111may be formed to extend between two non-adjacent negative supply rails152with all supply rails152or154that lie therebetween removed. For example, as shown in the embodiment ofFIG. 1B, positive supply rails154may be cut and removed at the location of decoupling cell column111so that they do not extend across the segments of a decoupling column111. In such a configuration, the severed or terminal ends of the positive supply rails154disposed on each side of a given decoupling column111may be connected together to bridge the gap, e.g., by an upper metal mesh layer (different layer) of the integrated circuit100to provide continuity. Similarly, one or more negative supply rails152may be cut and bridged in similar manner in those cases as illustrated inFIG. 1Bwhere a capacitor cell column111is formed to have a height greater than two times the height of the standard cell rows102, e.g., one negative supply rail152and two positive supply rails may be cut for a segment of a capacitor cell column111that has a height equal to four times the height of the standard cell rows102, two negative supply rails152and three positive supply rails may be cut for a segment of a capacitor cell column111that has a height equal to six times the height of the standard cell rows102, etc. In yet another embodiment, a segment of a capacitor cell column111may be formed between two adjacent and uncut negative supply rails152(with the intervening positive supply rail154being cut and bridged) so that the capacitor cell column111has a segment height that is equal to two times the height of standard cell rows102.

However, it is also possible in some embodiments that, where present, decoupling capacitor columns111may require more than one well be used (e.g., at least for the frontier between the route and the decoupling), which in some cases may exhibit lower efficiency than a row configuration. Additionally, when only decoupling capacitor cell rows110present, substantially no area efficiency penalty may result due to any space wasted in the interface between standard cell rows102and decoupling capacitor cell rows110. However, if a grid configuration is employed using capacitor cell columns, there may be a column of wasted space115(e.g., as required by appropriate minimum distance design rules) as illustrated inFIG. 1Bwhere each decoupling cell column111abuts each standard cell row102which has both pWell and nWell.

FIG. 3illustrates a simplified circuit schematic of digital circuitry area300(e.g., such as digital circuitry area209or210ofFIG. 2) of an IC390as it may be configured according to one exemplary embodiment. As shown inFIG. 3, circuitry area300includes decoupling capacitors formed in decoupling rows110that are placed in-between digital logic rows290which include active digital circuitry formed in standard cell rows102of IC200as previously described in relation toFIGS. 1 and 2. As shown, each of capacitors of decoupling capacitor rows110and active digital circuitry of digital logic rows290are coupled between positive supply rail154and negative supply rail152of IC200. Also illustrated inFIG. 3are positive supply pad310and negative supply pad312of IC390that are coupled to corresponding positive supply pin306and negative supply pin308by connectors302and304, e.g., lead frame connection wires. Regulator circuitry214is also shown coupled in the current path between supply pad310and positive voltage rail154.

FIG. 4illustrates a partial cross-sectional view of an integrated circuit400having a NMOS decoupling capacitor structure407formed on a silicon substrate410according to one exemplary embodiment. In this embodiment, integrated circuit400includes a deep nWell412formed within a p-type substrate410and having a single pWell406formed thereon that extends across a decoupling row110, e.g., within digital logic circuitry of a digital core208. Also shown inFIG. 4are N+ source and drain areas402and404formed within single pWell406. Decoupling capacitor structure407may in one embodiment extend across substantially the entire height of decoupling row110. As previously described, the polarity of the well used for a decoupling row110may be reversed, e.g., in an alternative embodiment a PMOS decoupling capacitor structure may be formed to include P+ source and drain areas formed in a single nWell that extends across a decoupling row110.

FIG. 5illustrates one exemplary embodiment of methodology500for decoupling capacitor selection and placement. Methodology500begins in step502with initial circuit placement and routing (P&R) for an IC200having analog circuitry and a digital core208with no decoupling capacitors yet placed. Methodology500then proceeds to step504in which current waveforms are extracted from the digital core (e.g., using a power simulator). Determination of the waveforms may be performed in one exemplary embodiment, for example, by either doing an hierarchical analysis or by powering up/down different digital blocks during simulation to determine the independent contributions. To determine the spurious content, digital blocks with backannotated parasitics may be simulated and the current waveform may be extracted from those simulations.

Next in step506, placement of the digital areas or blocks (e.g., subdivisions of digital logic active circuitry areas209and210ofFIG. 2) may be changed for the IC according to spurious content based on results of step504. In this regard, in one embodiment noisier digital blocks or areas may be placed farthest from the most noise sensitive analog circuit areas of the IC, e.g., in the manner illustrated and described in relation toFIG. 2herein. For example, the quietest (least noisy) digital blocks may be placed between the analog circuitry of the IC200and the noisier digital circuitry of the IC200, with the most noise sensitive analog circuitry of the IC200being placed farthest from the noisiest digital circuitry of the digital core.

Next, current waveforms may be again extracted in step508to determine if spurious content of the digital blocks/areas of the IC200are substantially homogenous across the digital core after the placement changes made in step506. In this regard, the current data from different blocks may be analyzed to determine if all blocks have the substantially the same spurious contribution making the spurious contributions substantially homogeneous. If not, then methodology500enters a block-by-block mode in step510, in which each of steps512to514are repeated for each given block of the digital core208before proceeding to step518. In this regard, for each given digital block the amount of decoupling capacitance may be calculated in step512that is needed to achieve the desired spur content for each block (e.g., to achieve a homogenous spur pickup), and this calculation then verified by simulation including regulator and coupling mechanisms. Next, in step514, the individual capacitor size may be optimized for the given block (e.g., based on the quality factor for an individual decoupling capacitor at the desired decoupling frequency). After step514, then equidistant decoupling rows110of decoupling capacitors may be placed for the given digital block in step516. After steps512to516have been performed for all digital blocks, then methodology500may proceed to step518, where the current waveforms across the digital core208may be extracted in step518to determine if homogeneous spur pickup across digital core208has been achieved. If so, then methodology500terminates in step520. If not, then methodology500returns to step510and steps512to516repeated for each digital block before returning to step518. It is noted that performance of block-by-block steps512-516may yield digital blocks that have different spacing of decoupling rows110from each other.

If in step508it is determined that the spurious content of the digital blocks/areas of the IC200are substantially homogenous across the digital core after the placement changes made in step506, then methodology proceeds to steps612,614and616in which methodology similar to corresponding steps152,514and516is repeated on for the digital core208as a whole rather than on a block-by-block basis. After steps612,614and616are performed, then step518is performed to determine if homogeneous spur pickup across digital core208has been achieved. If so, then methodology500terminates in step520, and steps612-616may yield a digital core208having consistent spacing of decoupling rows110. However, if not, then methodology500proceeds to step510and steps512to516performed for each digital block as previously described. It will be understood thatFIG. 5is exemplary only, and that any suitable combination of additional, alternative or fewer steps may be employed for decoupling capacitor configuration and placement according to the circuits and methods described herein.