Abstract:
Apparatuses, methods, and systems for effective power management distribution are provided. In an embodiment, a system for providing power to a circuit block comprises a power management unit (PMU) configured on a first substrate and an integrated circuit (IC) configured on a second substrate. The PMU includes a first regulator configured to step down an input voltage and output a first regulated voltage. The IC includes the circuit block and a second regulator configured to receive the first regulated voltage and output a second regulated voltage. The second power regulated voltage provides power to the circuit block. The first regulator is more efficient than the second regulator.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of U.S. Provisional Appl. No. 60/984,626, filed Nov. 1, 2007, which is incorporated by reference herein in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to providing power signals to devices, such as integrated circuit devices. 
         [0004]    2. Background Art 
         [0005]    A power management unit (PMU) can be used to control power provided to a variety of devices. For example, a PMU can be coupled to a battery and be used to provide power signals to an integrated circuit (IC) device. As IC devices often include circuit blocks having different requirements for their respective power supply signals, a PMU can be configured to output a variety of power supply signals with different properties. For example, the PMU can be configured to output low-noise power signals to be used by sensitive circuit blocks of the IC device. A PMU can also be used to manage the battery output to provide an uninterruptible power supply and to manage the recharging of the battery. 
         [0006]    A PMU and the IC devices for which the PMU controls power functions are typically mounted onto a printed circuit board (PCB). Power signals are transmitted from the PMU to the IC devices through interconnections, e.g., circuit traces, vias, signal planes, or a combination thereof. These interconnections take up space on the PCB in terms of: (1) the pins required on the PMU and IC devices to transmit and receive the power supply signals and (2) decoupling and/or compensation capacitors coupled to the interconnections that are used to enhance the stability of the power supply signals. 
         [0007]    Thus, what is needed are systems and methods that allow for power management to be distributed so as to satisfy the needs individual circuit blocks while efficiently using PCB space. 
       BRIEF SUMMARY 
       [0008]    Apparatuses, methods, and systems for effective power management distribution are described. In an embodiment, a system for providing power to a circuit block comprises a power management unit (PMU) configured on a first substrate and an integrated circuit (IC) configured on a second substrate. The PMU includes a first regulator configured to step down an input voltage and output a first regulated voltage. The IC includes the circuit block and a second regulator configured to receive the first regulated voltage and output a second regulated voltage. The second power regulated voltage provides power to the circuit block. The first regulator is more efficient than the second regulator. 
         [0009]    In another embodiment, a system for providing power includes a power management unit (PMU) configured on a first substrate and an integrated circuit (IC) configured on a second substrate. The PMU includes a first regulator configured to step down an input voltage and output a first regulated voltage. The IC includes a plurality of second regulators coupled to the first regulator and a plurality of circuit blocks. Each of the second regulators is configured to receive the first regulated voltage and output a respective second regulated voltage. Each circuit block is coupled to a respective second regulator and is configured to receive a respective second regulated voltage from the respective second regulator. The first regulator is more efficient than each second regulator. 
         [0010]    These and other advantages and features will become readily apparent in view of the following detailed description of the invention. Note that the Summary and Abstract sections may set forth one or more, but not all exemplary embodiments of the present invention as contemplated by the inventor(s). 
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
       [0011]    The accompanying drawings, which are incorporated herein and form a part of the specification, illustrate the present invention and, together with the description, further serve to explain the principles of the invention and to enable a person skilled in the pertinent art to make and use the invention. 
         [0012]      FIGS. 1 and 2  show block diagrams of systems that include a power management unit and an integrated circuit device. 
         [0013]      FIGS. 3 and 4  show block diagrams of systems that have distributed power management, according to embodiments of the present invention. 
         [0014]      FIG. 5  shows a circuit diagram of a conventional linear regulator. 
         [0015]      FIG. 6  shows a circuit diagram of a linear regulator, according to an embodiment of the present invention. 
         [0016]      FIG. 7  shows a flowchart providing example steps for assembling a system having distributed power management, according to an embodiment of the present invention. 
     
    
       [0017]    The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number identifies the drawing in which the reference number first appears. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    It is to be appreciated that the Detailed Description section, and not the Summary and Abstract sections, is intended to be used to interpret the claims. The Summary and Abstract sections may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way. 
         [0019]    The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed. 
         [0020]    The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance. 
         [0021]    The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. 
         [0022]      FIG. 1  shows a block diagram of a system  100  that includes a power management unit (PMU)  102  coupled to an integrated circuit (IC) device  104 . IC device  104  can be system-on-a-chip that has radio frequency (RF), baseband, frequency modulated (FM), multimedia, and/or mixed-signal audio applications. In an embodiment, system  100  is included in a mobile device, e.g., cellular phone, personal digital assistant, etc. 
         [0023]    PMU  102  includes switching regulators  106  and  108  and linear regulators  110 - 118 . Regulators  106 - 118  are coupled, directly or indirectly, to a battery (not shown) and generate regulated power signals that are used to power portions of IC device  104 . In an embodiment, linear regulators  110 - 118  can be low drop-out linear regulators. Low drop-out regulators are can operate with a relatively small difference between the voltage of an input signal, e.g., a battery signal or a signal received from a switching regulator, and a generated output signal. 
         [0024]    In an embodiment, switching regulators  106  and  108  are DC to DC converters that step down the voltage of the signal received from the battery. As would be understood by those skilled in the art, switching regulators can step down the voltage of a power signal more efficiently, i.e., dissipating less power, than can linear regulators. The added efficiency provided by switching regulators becomes especially important when high current power signals are provided. On the other hand, linear regulators can provide power signals that have relatively low noise when compared to power signals provided by switching regulators. To provide power for a circuit block that requires a low noise power supply signal and draws significant current, a switching regulator can be cascaded with a linear regulator to provide the benefits of both the switching regulator and linear regulator. For example, the switching regulator can step down the voltage efficiently and the linear regulator can receive the stepped down voltage and output another voltage has a higher signal to noise ratio (SNR) than the SNR of the stepped down voltage output by the switching regulator. For example, in  FIG. 1 , switching regulator  108  is cascaded with linear regulators  110  and  112  to provide power signals to a digital and an analog circuit block of IC  104 , respectively. In an embodiment, the circuit blocks coupled to linear regulators  110  and  112  are sensitive to noise in their respective power signals. 
         [0025]    Switching regulators  106  and  108  and linear regulators  110 - 118  can be configured to step up or step down an input voltage. For example, switching regulator  106  can be configured to step up or step down a received battery voltage. 
         [0026]    In another embodiment, a signal generated by a switching regulator can be used directly by a circuit block of IC device  104  without a linear regulator. For example, a power signal generated by switching regulator  106  can be received by digital circuit blocks of IC device  104  that are not as susceptible to noise as other circuit blocks of IC  104 . 
         [0027]    Linear regulators can also directly receive a power signal from the battery without the use of a switching regulator. For example, regulators  114 - 118  can be coupled directly to the battery. Linear regulators  114 - 118  can be coupled to circuit blocks in IC device  104  that do not draw significant current. Thus, the additional power dissipated by linear regulators  114 - 118 , as compared to a switching regulator, may not be significant. For example, regulators  114  and  116  may be coupled to analog circuit blocks of IC device  104  that do not draw significant current. Similarly, the linear regulator  118  can be coupled to an input/output (I/O) circuit block of IC device  104  that does not draw significant current. 
         [0028]    System  100  also includes inductors  120  and  122  coupled to switching regulators  106  and  108 , respectively. Inductors  120  and  122  can be used to further enhance the efficiency of switching regulators  106  and  108 . For example, electromagnetic fields built up in the cores of inductors  120  and  122  while switching regulators  106  and  108 , respectively, are in their “on” state can be discharged when switching regulators  106  and  108 , respectively are in their “off” state. Thus, an output signal is provided even when switching regulators  106  and  108  are in their “off” state. 
         [0029]    PMU  102  optionally includes a dynamic voltage management (DVM) control module  150  coupled to a DVM control module  152  included in IC device  104 . In an embodiment, DVM control module  150  is coupled to DVM control module  152  over a serial interface. DVM control module  152  can send signals to DVM control module  150  to dynamically manage the voltage of signals provided by PMU  102 . In such a manner, the voltage of signals provided to circuit blocks of IC device  104  can be decreased to save power and reduce heat dissipation. For example, if it is determined that a circuit block can be powered with a signal having a lower voltage than is presently provided, DVM control module  152  can send a signal to DVM control module DVM  150  requesting the voltage of that power signal be reduced. The reduced voltage may result in decreased performance of the circuit block, but the added battery life and/or decreased heat dissipation may outweigh the decrease in performance. 
         [0030]    In an embodiment, PMU  102  and IC device  104  are mounted onto a PCB. Each power supply signal provided by PMU  102  to IC device  104  results in at least one added interconnection between PMU  102  and IC device  104 . Each of these interconnections requires one or more pins on each of PMU  102  and IC device  104  and a capacitor coupled to each interconnection. The inventors have recognized that the significant number of capacitors required due to the interconnections and the potentially increased package size of PMU  102  and/or IC device  104  caused by the power pins can take up significant space on the PCB onto which PMU  102  and IC device  104  are mounted. 
         [0031]      FIG. 2  shows a system  200  that includes a PMU  202  and an IC device  204 . IC device  204  includes switching regulators  206  and  208  and linear regulators  210 - 218 . Similar to IC device  104  described with reference to  FIG. 1 , IC device  204  can also be a system-on-a-chip that has radio frequency (RF), baseband, frequency modulated (FM), multimedia, and/or mixed-signal audio applications. In a further embodiment, IC device  204  includes all of the circuit blocks, e.g., analog, digital, RF, I/O, that IC device  104  includes. In another embodiment, switching regulators  206  and  208  and linear regulators  210 - 218  are substantially similar to switching regulators  106  and  108  and linear regulators  110 - 118 , respectively, described with reference to  FIG. 1 . 
         [0032]    Switching regulator  208  is cascaded with linear regulators  210  and  212  to provide power signals to a digital and an analog circuit block of IC device  204 , respectively. In an embodiment, the circuit blocks coupled to linear regulators  210  and  212  are sensitive to noise in their respective power signals. 
         [0033]    A power signal generated by switching regulator  206  is received by digital circuit blocks of IC device  204  that are not as susceptible to noise as other circuit blocks of IC  204 . Linear regulators  214 - 218  can be coupled to circuit blocks in IC device  204  that do not draw significant current. As described above, in such an embodiment, the additional power dissipated through the use of linear regulators instead of switching regulators may not be significant. For example, linear regulators  214  and  216  may be coupled to analog circuit blocks of IC device  204  that do not draw significant current. Similarly, the linear regulator  218  can be coupled to an I/O circuit block of IC device  204  that does not draw significant current. 
         [0034]    IC device  204  also includes a DVM control module  252 . In an embodiment, DVM control module  252  is similar to DVM control module  152  described with reference to  FIG. 1 . However, in contrast to DVM control module  152 , DVM control module  252  does not transmit signals to a corresponding DVM module of a PMU, e.g., PMU  202 . Instead, DVM control module  252  dynamically adjusts the voltage of power supply signals by interacting with regulators  206 - 218  that are implemented in IC device  204 . 
         [0035]    System  200  also includes inductors  220  and  222 . In an embodiment, inductors  220  and  220  are substantially similar to inductors  120  and  122  described with reference to  FIG. 1 . 
         [0036]    Because IC device  204  includes regulators that generate power signals used by the circuit blocks of IC device  204 , interconnections between PMU  202  and IC device  204  can be limited. However, in some embodiments it is advantageous to have high power regulators implemented in a PMU. For example, the manufacturing technology used to fabricate a PMU may be better suited to handle regulators that generate high power signals than manufacturing technology used to fabricate IC device  204 . For example, PMU  202  may be fabricated such that it has larger line widths, e.g., approximately 0.35 μm, compared to line widths of IC device  204 , e.g., approximately 65 nm. In an embodiment, PMU  202  has larger line widths because it controls the charging of the battery. These larger line widths are better suited to handle high current associated with high power signals. Furthermore, in most systems, a PMU cannot be completely removed. For example, the PMU may handle certain tasks that a corresponding IC device does not, e.g., battery management and/or charging of the battery. 
       Exemplary Embodiments 
       [0037]    In embodiments described herein, power management is distributed between a PMU and device(s) to be powered by signals generated by the PMU. High-power regulators, e.g., regulators that can efficiently step down high power signals, such as switching regulators, are implemented in the PMU and low-power regulators, e.g., regulators used to provide low-noise and/or low power signals, such as linear regulators, are implemented in the device(s) to be powered. The inventors have found that by distributing power management as described herein, board space on a PCB can be saved and performance can be enhanced. For example, distributed power management, as described herein, can result in fewer interconnections between the PMU and the device(s) to be powered. Fewer interconnections can lead to fewer pins required for power functions on each of the PMU and the device(s) to be powered, possibly resulting in smaller IC packages for the PMU and/or device(s). Fewer interconnections also results in a reduced number of capacitors mounted to the PCB used to provide stability for the power supply signals transmitted over the interconnections. Furthermore, according to embodiments described herein, regulators can be assembled such that a capacitor may not be needed for some interconnections. Thus, the number of external capacitors can be reduced by reducing the number of interconnections to which external capacitors are typically coupled and designing regulators such that external capacitors may not be needed some of the remaining interconnections. A reduced number of interconnections can also result in enhanced performance through a reduction in the number of connections within the PMU and/or device(s), e.g., wire bond connections in a ball grid array package, resulting in a decreased inductance. As would be appreciated by those skilled in the art, inductance may introduce noise into the system. Performance of the overall system can also be improved by providing regulators customized for individual portions circuit blocks of the device(s) so as to increase isolation between portions of circuit blocks to reduce the effects of noise and to provide greater granularity in power supply signal properties. 
         [0038]      FIG. 3  shows a system  300  that has distributed power management, according to an embodiment of the present invention. System  300  includes a PMU  302  and an IC device  304 . PMU  302  includes switching regulators  306  and  308 . IC device  304  includes linear regulators  310 - 318 . Similar to IC device  104  described with reference to  FIG. 1 , IC device  304  can also be a system-on-a-chip that has radio frequency (RF), frequency modulated (FM), baseband, multimedia, and/or mixed-signal audio applications. In an embodiment, system  300  is included in a mobile device, e.g., cellular phone, personal digital assistant, etc. 
         [0039]    Switching regulators  306  and  308  and linear regulators  310 - 318  can be substantially similar to switching regulators  106  and  108  and linear regulators  110 - 118 , respectively, described with reference to  FIG. 1 . 
         [0040]    The manufacturing technology used to fabricate a PMU may be better suited to handle regulators that generate high power signals than manufacturing technology used to fabricate IC device  204 . For example, PMU  202  may be fabricated such that it has larger line widths, e.g., approximately 0.35 μm, compared to line widths of IC device  204 , e.g., approximately 65 nm. In an embodiment, PMU  202  has larger line widths because it controls the charging of the battery. These larger line widths are better suited to handle high current associated with high power signals. 
         [0041]    As shown in  FIG. 3 , power management and regulation is split between PMU  302  and IC device  304 . Specifically, switching regulators  306  and  308  that are configured to provide high power, e.g., high current, signals are implemented in PMU  302 . Linear regulators  310  and  312  that receive signals from switching regulator  308  and linear regulators  314 - 318  that provide relatively low power signals, e.g., low current, are implemented in IC device  304 . As shown in  FIG. 3 , switching regulator  306  directly powers one or more circuit blocks of IC device  304 . For example, switching regulator  306  can provide power signals to digital circuit blocks of IC device  304  that can operate with relatively noisy power signals. Switching regulator  308  is cascaded with linear regulators  310  and  312  to provide low noise and relatively high power signals to digital and analog circuit blocks of IC device  304 , respectively. In an embodiment, circuit blocks that receive signals from linear regulators  310  and  312  can be especially susceptible to noise. For example, these circuit blocks may include radio frequency (RF) and/or analog components. Linear regulators  314 - 318  are directly coupled to the battery. Similar to regulators  114 - 118  described with respect to  FIG. 1 , regulators  314 - 318  can be configured to provide relatively low power so that the inefficiency of linear regulators  314 - 318 , compared to switching regulators, does not result in significant power being wasted. In an embodiment, linear regulators  314  and  316  can be used to provide power signals for analog circuit blocks of IC device  304 . Linear regulator  318  can be used to provide a power signal to an I/O circuit block of IC device  304 . 
         [0042]    PMU  302  and IC device  304  also optionally include respective DVM control modules  350  and  352 . DVM control module  352  can be configured to dynamically manage the voltage of signals provided by linear regulators  310 - 318 . Furthermore, DVM control module  352  can transmit signals to DVM control module  350  of PMU  302  to adjust the voltage of power signals generated by switching regulators  306  and  308 . In such a manner, DVM control module  352  of IC device  304  can optimize the voltage of power signals provided to various circuit blocks of IC device  304  to maximize the life of the battery and/or reduce heat dissipation. 
         [0043]    By splitting the power management and regulation responsibilities as shown in  FIG. 3 , the number of interconnections between PMU  302  and IC device  304  can be substantially reduced, as compared to system  100  shown in  FIG. 1 . The reduced interconnections results in a reduction in the number of capacitors and reduces the total pin count for each of PMU  302  and IC device  304 . Capacitors coupled to interconnections can take up substantial space on a PCB onto which PMU  302  and IC device  304  are mounted. By reducing the number of interconnections, the number of these capacitors can be reduced. Reducing the pin counts of PMU  302  and IC device  304  can also result in smaller packages for PMU  302  and IC device  304  and a reduced number of interconnections, e.g., wire bond connections, within each IC package. As described above, a reduced number of interconnections within the IC packages can result in a reduced inductance, and thus reduced noise. Furthermore, system  300  also retains the cost benefits of having high power switching regulators  306  and  308  implemented in PMU  302 . 
         [0044]      FIG. 4  shows a system  400  having distributed power management, according to an embodiment of the present invention. System  400  includes a PMU  402  and an IC device  404 . PMU  402  includes switching regulators  404  and  406 , 5-Volt (V) power supply  408 , a wall charger/USB charger  410 , a battery manager  412 , a pulse width modulated (PWM) signal module  414 , a DVM control module  416 , a real time clock  418 , a one-time programmable (OTP) memory  420 , and amplifiers  422 . IC device  404  includes analog circuit blocks  424  and  426 , a multimedia processor  428 , linear regulators  430 - 436 , a linear regulator  438 , a DVM control module  440 , and switches  442  and  444 . 
         [0045]    In an embodiment, IC device  404  includes a core portion that includes example analog circuit blocks  424  and  426 , a multimedia processor  428 , and linear regulators  430 - 436 . This portion of IC device  404  can provide the main features to be provided by IC device  404 . Other portions of IC device  404 , e.g., a circuit block coupled to linear regulator  438 , can provide other non-essential or optional features of IC device  404 . 
         [0046]    Similar to system  300  shown in  FIG. 3 , power management and regulation in system  400  is split between PMU  402  and IC device  404 . Specifically, high power regulators are implemented in PMU  402  and low power regulators are implemented in IC device  404 . As shown in  FIG. 4 , switching regulator  404  is coupled to a 5V battery and outputs a power signal having a total current of 900 milliamperes (mA) at a voltage of 1.2 V, for example purposes. Of the total 900 mA output by switching regulator  404 , 280 mA are received by an SDRAM memory module (not shown). The remaining 700 mA is received by components of IC device  404 . The voltage and current values described herein are only exemplary, and not intended to limit the invention. For example, the remaining 700 mA can be split amongst analog circuit blocks  424  and  426  and multi-media processor  428 . Also shown in  FIG. 4 , analog circuit block  426  and multi-media processor  428  are coupled to the power signal provided by switching regulator  404  through switches  442  and  444 , respectively. Switches  442  and  444  can be used to deactivate analog circuit block  426  and multi-media processor  428 , respectively, when they are not in use to save power. When they are deactivated, switching regulator  404  may output a signal with reduced current since analog circuit block  426  and multi-media processor  428  are no longer drawing current. 
         [0047]    Switching regulator  406  of PMU  402  is cascaded with linear regulator  430  of IC device  404 . Switching regulator  406  outputs a power signal having 100 mA at a voltage of 1.5 V. This power signal is received by linear regulator  430  which further steps down the voltage to generate a power signal that has a voltage of 1.2 V and a current of 100 mA. 5V power supply  408  outputs a signal having a current of 55 mA at a voltage of 5V to an HDMI terminal (not shown). Wall charger/USB module  410  is used to charge the battery based on a power signal received from a wall socket or a USB connection. Battery manager  412  is used to manage the output of the battery and to provide an uninterruptible power supply. PWM module  414  is used to output a PWM signal that is used to control devices of PMU  402  such as light emitting diodes (LED). Real time clock  418  is used to provide a clock signal for the operation of PMU  402 . OTP memory  420  permanently stores internal settings of PMU  402  such as the settings of switching regulators  404  and  406 . Amplifiers  422  are used to amplify power and/or audio signals. In a further embodiment, amplifiers  422  include class D amplifiers that are highly efficient and used for audio or power signals. 
         [0048]    Analog circuit blocks  424  and  426  and multi-media processor  428  receive a power signal directly from switching regulator  404 , i.e., without a linear regulator in between. In an embodiment, analog circuit blocks  424  and  426  and multi-media processor  428  are less susceptible to noise in their respective power supply signals than other circuit blocks of IC device  404 . Linear regulator  430  is cascaded with switching regulator  406  to provide a low noise high power, e.g., high current, signal efficiently to an analog circuit block. This analog circuit block may be especially susceptible to noise in its power supply signal. Linear regulators  432 - 438  are coupled to the battery power signal. Each of linear regulators  432 - 438  provide a signal having a known current, 50 mA. As compared to the other power signals provided in system  400 , 50 mA of current is relatively small, thus the inefficiency added by using a linear regulator instead of a switching regulator is not significant. For example, linear regulators  432 - 434  can provide power signals to analog circuit blocks at voltages of 2.5V and 3.0V, respectively. Voltage regulator  436  can provide a power signal to an I/O module at a voltage of 1.8V for example. Linear regulator  438  can provide a power signal to an audio module having a voltage of 3.0V for example. One or more of linear regulators  430 - 438  can be low drop out linear regulators. 
         [0049]    DVM control modules  440  and  416  can be used to dynamically manage the voltage of power signals so as to maximize the life of the battery and/or reduce heat dissipation. For example, DVM control module  440  of IC device  404  can adjust the output voltages of regulators  430 - 438  based on the needs of circuit blocks coupled to each regulator. DVM control module  440  can also transmit signals to DVM control module  416  based on which DVM control module  416  can adjust the output voltages of switching regulators  404  and  406 . 
         [0050]    By splitting the power management and regulation responsibilities as shown in system  400 , the benefits of having high power switching regulators implemented in PMU  402  are retained while reducing the number of interconnections between PMU  402  and IC device  404 . As described above, reducing the number of interconnections between PMU  402  and IC device  404  can save space on a PCB onto which PMU  402  and IC device  404  are mounted through a reduction in the number of capacitors that have to be mounted onto the PCB and a decrease in the size of the packages of PMU  402  and IC device  404 . 
         [0051]      FIG. 5  shows a circuit diagram of a conventional linear regulator  500  coupled to an analog IP or digital core  550 . Linear regulator  500  and core  550  are typically implemented in separate IC packages and coupled together through interconnections on a PCB. For example, linear regulator  500  can be used in one or more of linear regulators  114 - 118  described with respect to  FIG. 1 . Linear regulator  500  includes a metal oxide semiconductor field effect transistor (MOSFET)  504 , an operational amplifier  506 , resistors  510  and  512 , and a capacitor  516 . As shown in  FIG. 5 , a source of MOSFET  504  is coupled to a node  502  that is held at a predetermined voltage, approximately 1.5V for example. For example, MOSFET  504  may be coupled to a switching regulator that outputs a power signal having a voltage of 1.5V. Operational amplifier  506 , which receives a reference voltage  508 , is coupled to a gate of MOSFET  504 . Resistors  510  and  512  form a voltage divider. 
         [0052]    As would be appreciated by those skilled in the art, the feedback loop of linear regulator  500  formed by operational amplifier  506 , MOSFET  504 , and resistors  510  and  512  tends to hold the voltage at a node  514  at a desired value, e.g., about 1.2V. The value of the voltage at node  514  is principally determined by the values of resistors  510  and  512 , the voltage received at a source  502  of MOSFET  504  and voltage reference  508  received by operational amplifier  506 . In an embodiment, the values of these parameters are set so that a desired 1.2V output is obtained at node  514 . 
         [0053]    Linear regulator  500  also requires an external capacitor  516 . Since the load of core  550  that is to be powered by an output of linear regulator  500  is unknown when linear regulator  500  is designed and the output of linear regulator  500  is used to power a device or circuit block  550  implemented in another IC, linear regulator  500  is designed so that its dominant pole is at node  514 . Such a design provides adequate stability for a variety of loads provided by analog or digital core  550 . However, such a design also requires an external capacitor. For example, the external capacitor may be coupled to an interconnection between a PMU and an IC device, e.g., PMU  302  and IC device  304  in  FIG. 3 . As described above, external capacitors coupled to interconnections take up significant space on a PCB. If space on the PCB is be saved, additional components could be mounted on the PCB, giving the total system added functionality. Alternatively, the saved space could be used to decrease the overall size of the PCB. 
         [0054]      FIG. 6  shows a circuit diagram of a linear regulator  600  coupled to a circuit block  650 , according to an embodiment of the present invention. Linear regulator  600  includes a MOSFET  604 , and operational amplifier  606 , resistors  610  and  612 , and a capacitor  616 . MOSFET  604 , operational amplifier  606 , and resistors  610  and  612  can be substantially similar to MOSFET  504 , operational amplifier  506 , and resistors  510  and  512 , respectively, described with reference to  FIG. 5  above. 
         [0055]    In contrast to linear regulator  500  shown in  FIG. 5 , linear regulator  600  is used to power a specific circuit block  650 . For example, circuit block  650  may be a phase locked loop (PLL) or an analog-to-digital converter (ADC). Linear regulator  600  is included within the analog or digital device. Thus, the load of circuit block  650  is known when linear regulator  600  is implemented. The inventors have found that when the load of the circuit block to be powered is known before linear regulator  600  is implemented a design for linear regulator  600  can be used that does not have to provide stability for in all types of situations. For example, the dominant pole of linear regulator  600  is no longer located at a output node  614  but rather is located at the gate of MOSFET  604 . As such, an internal compensation or decoupling capacitor can be used. Thus, instead of having an external capacitor, e.g., capacitor  516  as shown in  FIG. 5 , linear regulator  600  has an internal capacitor. By including the capacitor within the linear regulator and not using an external capacitor significant board space on a PCB can be saved. Furthermore, since linear regulator  600  provides a power signal to specific portions of a circuit block, the properties of the power supply signals, e.g., voltage, can be customized. Thus, greater granularity in power supply signal properties can be achieved by using a regulator similar to linear regulator  600  shown in  FIG. 6 . 
         [0056]    In embodiments where linear regulator  600  is used in a system that has distributed power supply management, as described above, significant space on a PCB can be saved. Specifically, the number of interconnections can be reduced and some external capacitors that would be coupled to the remaining interconnections can be eliminated. 
         [0057]      FIG. 7  shows a flow chart providing a method of assembling a system with distributed power management, according to an embodiment of the present invention. Other structural and operational embodiments will be apparent to persons skilled in the relevant art(s) based on the following discussion. The steps shown in  FIG. 7  do not necessarily have to occur in the order shown. The steps of  FIG. 7  are described in detail below. 
         [0058]    Flow chart  700  begins with step  702 . In step  702 , a load of a circuit block to be powered is determined. For example, in  FIG. 6 , the load of a circuit block  650  can be determined. 
         [0059]    In step  704 , a regulator is provided that generates a signal used to power the circuit block. The regulator can include an internal capacitor that has a capacitance determined based on the load of the circuit block determined in step  702 . For example, in  FIG. 6 , linear regulator  600  is provided that includes an internal capacitor  616  that has a capacitance determined by a load of circuit block  650 . 
         [0060]    In step  706 , a power management unit is provided that includes high power regulators. For example in  FIG. 3 , PMU  302  that includes switching regulators  306  and  308  can be provided. 
         [0061]    In step  708  the IC device and the PMU are mounted onto a PCB. For example, PMU  302  and IC device  304  shown in  FIG. 3  can be mounted onto a PCB. 
         [0062]    In step  710 , interconnections are formed between the PMU, IC device, and battery. In an embodiment, one or more interconnections do not require a capacitor because the capacitor has been implemented within the regulators included in the IC device. 
         [0063]    As described above, the steps of flow chart  700  do not have to occur in the order shown. For example, the order of steps  708  and  710  can be reversed. In such an embodiment, the interconnections are formed on a PCB before the IC device and PMU are mounted onto the PCB. 
         [0064]    Conclusion 
         [0065]    While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.