Abstract:
A power supply control apparatus includes a plurality of power supply units for supplying electric power to a plurality of electric circuits respectively. The power supply control apparatus receives pulse signals from the exterior. Each of the plurality of power supply units comprises a counter for counting the pulse signals. And a controller initiates to supply of the electric power to corresponding one of the electric circuits when the number of the pulse signals counted by the counter reaches the particular value which corresponds to an initiating timing of supplying electric power to corresponding one of the electric circuits.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based upon and claims the benefit of priority of the prior Japanese Patent Application No. 2009-12363, filed on Jan. 22, 2009, the entire contents of which are incorporated herein by reference. 
       FIELD 
       [0002]    The embodiments discussed herein are related to a power supply control apparatus. 
       BACKGROUND 
       [0003]    Devices such as LSIs (Large Scale Integrations) that use a plurality of power supplies, for example, a core power supply, an I/O (Input/Output) power supply, and the like often do not normally operate unless a proper power supply sequence is kept. Accordingly, various power supply control apparatus are devised and put into practical use to control the power supply sequence. A first power supply control apparatus (refer to, for example, Japanese Patent Application Laid-Open No. 2004-180385) and a second power supply control apparatus will be sequentially explained below as examples of conventional power supply control apparatus. 
         [0004]    First, the first conventional power supply control apparatus will be explained.  FIG. 7  is a view illustrating a configuration of the first conventional power supply control apparatus. As shown in  FIG. 7 , the first power supply control apparatus  10  has an input supply power source  11 , DC-DC converters  12   a  to  12   c,  voltage monitoring circuits  13   a,    13   b,  and a load circuit  14 . 
         [0005]    The input supply power source  11  is a circuit for supplying a voltage to the DC-DC converters  12   a  to  12   c.  A plus terminal of the input supply power source  11  is connected to Vin (+) of each of the DC-DC converters  12   a  to  12   c,  and a minus terminal of the input supply power source  11  is connected to Vin (−) of each of the DC-DC converters  12   a  to  12   c.  A voltage supplied from the input supply power source  11  to the DC-DC converters  12   a  to  12   c  is shown by Vin. 
         [0006]    Each of the DC-DC converters  12   a  to  12   c  is a circuit which has Vin (+), Vin (−), Vout (+), Vout (−) and ON/OFF terminals, and supplies power to the load circuit  14  when it receives power from the input supply power source  11  and the ON/OFF terminal is turned “ON”. In the following explanation, voltages supplied from the DC-DC converters  12   a  to  12   c  to the load circuit  14  are shown by Vout  1  to Vout  3 . 
         [0007]    The voltage monitoring circuit  13   a  is a circuit which is connected to Vout (+) and Vout (−) of the DC-DC converter  12   a  and sets the ON/OFF terminal of the DC-DC converter  12   b  to “ON” when it detects Vout  1  supplied from the DC-DC converter  12   a  to the load circuit  14 . 
         [0008]    The voltage monitoring circuit  13   b  is a circuit which is connected to Vout (+) and Vout (−) of the DC-DC converter  12   b  and sets the ON/OFF terminal of the DC-DC converter  12   c  to “ON” when it detects Vout  2  supplied from the DC-DC converter  12   b  to the load circuit  14 . 
         [0009]    The load circuit  14  is a circuit for executing various processing making use of the voltages sequentially supplied from the DC-DC converters  12   a  to  12   c.    
         [0010]    Next, operation waveforms of the first power supply control apparatus shown in  FIG. 7  will be explained.  FIG. 8  is a view illustrating the operation waveforms of the first power supply control apparatus. Note that the ON/OFF terminal of the DC-DC converter  12   a  is turned “ON”. 
         [0011]    When the input supply power source  11  supplies Vin to the DC-DC converters  12   a  to  12   c  (refer to Vin of  FIG. 8 ), since the ON/OFF terminal of the DC-DC converter  12   a  is turned “ON”, Vout  1  is output from the DC-DC converter  12   a  (refer to Vout  1  of  FIG. 8 ). 
         [0012]    When the voltage monitoring circuit  13   a  detects Vout  1  from the DC-DC converter  12   a,  the voltage monitoring circuit  13   a  applies a voltage S 1  to the ON/OFF terminal of the DC-DC converter  12   b  (refer to S 1  of  FIG. 8 ), and the ON/OFF terminal of the DC-DC converter  12   b  is turned “ON”. When the ON/OFF terminal of the DC-DC converter  12   b  is turned “ON”, the Vout  2  is output from the DC-DC converter  12   b  (refer to Vout  2  of  FIG. 8 ). 
         [0013]    When the voltage monitoring circuit  13   b  detects Vout  2  from the DC-DC converter  12   b,  the voltage monitoring circuit  13   b  applies a voltage S 2  to the ON/OFF terminal of the DC-DC converter  12   c  (refer to S 2  of  FIG. 8 ), and the ON/OFF terminal of the DC-DC converter  12   c  is turned “ON”. When the ON/OFF terminal of the DC-DC converter  12   c  is turned “ON”, Vout  3  is output from the DC-DC converter  12   c  (refer to Vout  3  of  FIG. 8 ). 
         [0014]    As described above, in the first power supply control apparatus  10 , when, for example, powers are supplied to the load circuit  14  in the sequence of the DC-DC converters  12   a  to  12   c,  the DC-DC converters  12   a  to  12   c  are sequentially connected in this power supply sequence, and the voltage monitoring circuits  13   a ,  13   b  turn “ON” and “OFF” the ON/OFF terminals of the DC-DC converters  12   b,    12   c.    
         [0015]    Next, the second conventional power supply control apparatus will be explained.  FIG. 9  is a view illustrating a configuration of the second conventional power supply control apparatus. As shown in  FIG. 9 , the second power supply control apparatus  20  has an input supply power source  21 , DC-DC converters  22   a  to  22   c,  a delay signal circuit  23 , and a load circuit  24 . 
         [0016]    The input supply power source  21  is a circuit for supplying a voltage to the DC-DC converters  22   a  to  22   c.  A plus terminal of the input supply power source  21  is connected to Vin (+) of each of the DC-DC converters  22   a  to  22   c,  and a minus terminal of the input supply power source  21  is connected to Vin (−) of each of the DC-DC converters  22   a  to  22   c.  A voltage supplied from the input supply power source  21  to the DC-DC converters  22   a  to  22   c  is shown by Vin. 
         [0017]    Each of the DC-DC converters  22   a  to  22   c  is a circuit which has Vin (+), Vin (−), Vout (+), Vout (−) and ON/OFF terminals and supplies power to the load circuit  24  when it receives power from the input supply power source  21  and the ON/OFF terminal is turned “ON”. In the following explanation, voltages supplied from the DC-DC converters  22   a  to  22   c  to the load circuit  24  are shown by Vout  1  to Vout  3 . 
         [0018]    The delay signal circuit  23  is a circuit for outputting control signals to the DC-DC converters  22   a  to  22   c  according to a power supply sequence and sequentially turning “ON” the ON/OFF terminals of the DC-DC converters  22   a  to  22   c . When, for example, voltages are sequentially supplied to the load circuit  24  in the order of Vout  1  to Vout  3 , the delay signal circuit  23  inputs control signals S 1  to S 3  in the order of the DC-DC converters  22   a  to  22   c.    
         [0019]    The load circuit  24  is a circuit for executing various processing making use of the voltages sequentially supplied from the DC-DC converters  22   a  to  22   c.    
         [0020]    Next, operation waveforms of the second power supply control apparatus  20  shown in  FIG. 9  will be explained.  FIG. 10  is a view illustrating the operation waveforms of the second power supply control apparatus  20 . Note that a case where voltages are supplied to the load circuit  24  in the order of Vout  1  to Vout  3  will be explained here as an example. 
         [0021]    The input supply power source  21  supplies Vin to the DC-DC converters  22   a  to  22   c  (refer to Vin of  FIG. 10 ). When the delay signal circuit  23  outputs a control signal S 1  to the DC-DC converter  22   a  (refer to S 1  of  FIG. 10 ), the ON/OFF terminal of the DC-DC converter  22   a  is turned “ON”, and Vout  1  is output from the DC-DC converter  22   a  (refer to Vout  1  of  FIG. 10 ). 
         [0022]    When the delay signal circuit  23  outputs a control signal S 2  to the DC-DC converter  22   b  at a predetermined time interval after it outputs the control signal S 1  to the DC-DC converter  22   a  (refer to S 2  of  FIG. 10 ), the ON/OFF terminal of the DC-DC converter  22   b  is turned “ON”, and Vout  2  is output from the DC-DC converter  22   b  (refer to Vout  2  of  FIG. 10 ). 
         [0023]    When the delay signal circuit  23  outputs a control signal S 3  to the DC-DC converter  22   c  at a predetermined time interval after it outputs the control signal S 2  to the DC-DC converter  22   b  (refer to S 3  of  FIG. 10 ), the ON/OFF terminal of the DC-DC converter  22   c  is turned “ON”, and Vout  3  is output from the DC-DC converter  22   c  (refer to Vout  3  of  FIG. 10 ). 
         [0024]    In the second power supply control apparatus, when, for example, powers are supplied to the load circuit  24  in the order of the DC-DC converters  22   a  to  22   c  as described above, the delay signal circuit  23  sequentially inputs the control signals S 1  to S 3  to the ON/OFF terminals of the DC-DC converters  22   a  to  22   c  in this sequence. 
         [0025]    However, when the first power supply control apparatus  10  is assembled to an actual device and a power supply sequence is controlled, it is preferable to control a start-up sequence between elements in addition to the power supply sequence to the load circuit.  FIG. 11  is a view illustrating an example where the first power supply control apparatus  10  is assembled to the actual device. As shown in  FIG. 11 , since it is preferable to control many DC-DC converters to control the power supply sequence to a plurality of LSIs, a start-up sequence becomes complex. Further, in the first power supply control apparatus  10 , signal wires is connected to each other between the DC-DC converters according to the start-up sequence and thus many signal wires are wired in a complex fashion. Since various controls are executed on a highly dense wiring substrate in addition to a control of a power supply sequence, a space for wiring many wires does not remain in the wiring substrate unlike the first power supply control apparatus  10 . 
         [0026]    Further, once the first power supply control apparatus  10  is assembled to the actual device, it is very difficult to change a start-up sequence because destinations of connections of signal wires may be changed. Note that there is a possibility of avoiding difficulty of changing the start-up sequence by assembling the second power supply control apparatus  20  to an actual device. However, even if the second power supply control apparatus  20  is used, since different signal lines are connected from the delay signal circuit  23  to the DC-DC converters, a problem of pressing a region on a wiring substrate may not be overcome as in the first power supply control apparatus  10 . 
       SUMMARY 
       [0027]    According to an aspect of the embodiment, a power supply control apparatus includes a plurality of power supply units for supplying electric power to a plurality of electric circuits respectively, the power supply apparatus receiving pulse signals from the exterior, each of the plurality of power supply units comprising; a counter for counting the pulse signals and, a controller for initiating to supply of the electric power to corresponding one of the electric circuits when the number of the pulse signals counted by the counter reaches the particular value which corresponds to a initiating timing of supplying electric power to corresponding one of the electric circuits. 
         [0028]    The object and advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the claims. 
         [0029]    It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are not restrictive of the invention, as claimed. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0030]      FIG. 1  is a view illustrating a configuration of a power supply control apparatus according to Embodiment 1; 
           [0031]      FIG. 2  is a view illustrating operation waveforms of the power supply control apparatus according to Embodiment 1; 
           [0032]      FIG. 3  is a view for explaining a shift number setting unit and a shift register unit according to Embodiment 1 in detail; 
           [0033]      FIG. 4  is a view illustrating operation waveforms of a pulse signal generating circuit, a shift register, an AND circuit, and an OR circuit; 
           [0034]      FIG. 5  is a view illustrating a configuration of a power supply control apparatus according to Embodiment 2; 
           [0035]      FIG. 6  is a view illustrating operation waveforms of the power supply control apparatus according to Embodiment 2; 
           [0036]      FIG. 7  is a view illustrating a configuration of a first conventional power supply control apparatus; 
           [0037]      FIG. 8  is a view illustrating operation waveforms of the first power supply control apparatus; 
           [0038]      FIG. 9  is a view illustrating a configuration of a second conventional power supply control apparatus; 
           [0039]      FIG. 10  is a view illustrating operation waveforms of the second power supply control apparatus; and 
           [0040]      FIG. 11  is a view illustrating an example where the first power supply control apparatus is assembled to an actual device. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiment 1 
       [0041]    When a power supply control apparatus according to Embodiment 1 controls a power supply sequence to a load circuit, respective DC-DC converters control the power supply sequence by adjust timings at which they output powers based on the pulse number included in the pulse signal. 
         [0042]    Next, a configuration of the power supply control apparatus according to Embodiment 1 will be explained.  FIG. 1  is a view illustrating a configuration of the power supply control apparatus according to Embodiment 1. As shown in  FIG. 1 , a power supply control apparatus  100  has an input supply power source  110 , a pulse signal generating circuit  120 , DC-DC converters  130  to  150 , and a load circuit  160 . 
         [0043]    The input supply power source  110  is a circuit for supplying a voltage to the DC-DC converters  130  to  150 . A plus terminal of the input supply power source  110  is connected to Vin (+) of each of the DC-DC converters  130  to  150 , and a minus terminal of the input supply power source  110  is connected to Vin (−) of each of the DC-DC converters  130  to  150 . The voltage supplied from the input supply power source  110  to the DC-DC converters  130  to  150  is shown by Vin. 
         [0044]    The pulse signal generating circuit  120  is a circuit for generating a pulse signal. The pulse signal generating circuit  120  outputs the generated pulse signal to the DC-DC converters  130  to  150 . 
         [0045]    The DC-DC converter  130  is a circuit for obtaining the pulse signal from the pulse signal generating circuit  120  and outputting a voltage Vout  1  to the load circuit  160  when the pulse number of the obtained pulse signal reaches a predetermined number. Specifically, the DC-DC converter  130  has a shift number setting unit  130   a  and a shift register unit  130   b.  Note that the DC-DC converter  130  has Vin (+), Vin (−), Vout (+), Vout (−), and ON/OFF terminals as terminals. 
         [0046]    The shift number setting unit  130   a  is a circuit for setting a pulse number of a pulse signal acting as a timing at which the Vout  1  is output. In the following explanation, the pulse number set by the shift number setting unit  130   a  is shown as a first pulse number. 
         [0047]    The shift register unit  130   b  is a circuit for counting the pulse number of the pulse signal output from the pulse signal generating circuit  120  and turns “ON” the ON/OFF terminal when the counted pulse number reaches the first pulse number. When the ON/OFF terminal of the DC-DC converter  130  is turned “ON” in a state that Vin is applied thereto from the input supply power source  110 , the DC-DC converter  130  outputs the voltage Vout  1  to the load circuit  160 . 
         [0048]    The DC-DC converter  140  is a circuit for obtaining the pulse signal from the pulse signal generating circuit  120  and outputting a voltage Vout  2  to the load circuit  160  when the pulse number of the obtained pulse signal reaches a predetermined number. Specifically, the DC-DC converter  140  has a shift number setting unit  140   a  and a shift register unit  140   b.  Note that the DC-DC converter  140  has Vin (+), Vin (−), Vout (+), Vout (−), and ON/OFF terminals as terminals. 
         [0049]    The shift number setting unit  140   a  is a circuit for setting a pulse number of a pulse signal acting as a timing at which Vout  2  is output. In the following explanation, the pulse number set by the shift number setting unit  140  is shown as a second pulse number. 
         [0050]    The shift register unit  140   b  is a circuit for counting the pulse number of the pulse signal output from the pulse signal generating circuit  120  and turns “ON” the ON/OFF terminal when the counted pulse number reaches the second pulse number. When the ON/OFF terminal of the DC-DC converter  140  is turned “ON” in a state that Vin is applied thereto from the input supply power source  110 , the DC-DC converter  140  outputs the voltage Vout  2  to the load circuit  160 . 
         [0051]    The DC-DC converter  150  is a circuit for obtaining the pulse signal from the pulse signal generating circuit  120  and outputting a voltage Vout  3  to the load circuit  160  when the pulse number of the obtained pulse signal reaches a predetermined number. Specifically, the DC-DC converter  150  has a shift number setting unit  150   a  and a shift register unit  150   b.  Note that the DC-DC converter  150  has Vin (+), Vin (−), Vout (+), Vout (−), and ON/OFF terminals as terminals. 
         [0052]    The shift number setting unit  140   a  is a circuit for setting a pulse number of a pulse signal acting as a timing at which Vout  3  is output. In the following explanation, the pulse number set by the shift number setting unit  150   a  is shown as a third pulse number. 
         [0053]    The shift register unit  150   b  is a circuit for counting the pulse number of the pulse signal output from the pulse signal generating circuit  120  and turns “ON” the ON/OFF terminal when the counted pulse number reaches the third pulse number. When the ON/OFF terminal of the DC-DC converter  150  is turned “ON” in a state that Vin is applied thereto from the input supply power source  110 , the DC-DC converter  150  outputs the voltage Vout  3  to the load circuit  160 . 
         [0054]    The load circuit  160  is a circuit for executing various processes making use of the voltages sequentially supplied from the DC-DC converters  130  to  150 . A core circuit, an IO circuit, and various LSIs, for example, are mounted on the load circuit  160 . 
         [0055]    A sequence of the first, second, and third pulse numbers set to the shift register units  130   b  to  150   b  may be sufficiently adjusted according to the power supply sequence of the voltages Vout  1  to  3  to adjust the power supply sequence of the voltages Vout  1  to  3  supplied to the load circuit  160 . When, for example, the voltages Vout  1 , Vout  2 , and Vout  3  are sequentially supplied to the load circuit  160  in this order, the first, second, and third pulse numbers may be sufficiently adjusted such that first pulse number&lt;second pulse number&lt;third pulse number. 
         [0056]    Next, operation waveforms of the power supply control apparatus  100  shown in  FIG. 1  will be explained.  FIG. 2  is a view illustrating the operation waveforms of the power supply control apparatus  100  according to Embodiment 1. Note that the first pulse number of the shift register unit  130   b  is set to “1”, the second pulse number of the shift register unit  140   b  is set to “2”, and the third pulse number of the shift register unit  150   b  is set to “6” as an example. 
         [0057]    The input supply power source  110  starts to supply Vin (refer to Vin of  FIG. 2 ) to the DC-DC converters  130  to  150  while the pulse signal generating circuit  120  outputs the pulse signal to the DC-DC converters  130  to  150  (refer to clock signal of  FIG. 2 ). 
         [0058]    The shift register unit  130   b  obtains the pulse signal output from the pulse signal generating circuit  120  and outputs a control signal S 1  to the ON/OFF terminal (refer to S 1  of  FIG. 2 ) at the time the pulse number becomes “1” to thereby turn “ON” the ON/OFF terminal. When the ON/OFF terminal is turned “ON”, the DC-DC converter  130  outputs Vout  1  (refer to Vout  1  of  FIG. 2 ). 
         [0059]    The shift register unit  140   b  obtains the pulse signal output from the pulse signal generating circuit  120  and outputs a control signal S 2  to the ON/OFF terminal at the time the pulse number becomes “2” (refer to S 2  of  FIG. 2 ) to thereby turn “ON” the ON/OFF terminal. When the ON/OFF terminal is turned “ON”, the DC-DC converter  140  outputs Vout  2  (refer to Vout  2  of  FIG. 2 ). 
         [0060]    The shift register unit  150   b  obtains the pulse signal output from the pulse signal generating circuit  120  and outputs a control signal S 3  to the ON/OFF terminal at the time the pulse number becomes “6” (refer to S 3  of  FIG. 6 ) to thereby turn “ON” the ON/OFF terminal. When the ON/OFF terminal is turned “ON”, the DC-DC converter  150  outputs Vout  3  (refer to Vout  3  of  FIG. 2 ). 
         [0061]    As described above, in Embodiment 1, a timing at which the voltage is output to the load circuit  160  is determined and the voltage is output to the load circuit  160  by that the pulse signal generating circuit  120  outputs the pulse signals to the DC-DC converters  130  to  150  using one start-up signal line and the DC-DC converters  130  to  150  count the pulse numbers of the pulse signals, respectively. As a result, the power supply sequence to the load circuit can be accurately controlled without pressing a wiring region of a highly dense wiring substrate. 
         [0062]    Next, the shift number setting unit and the shift register unit shown in  FIG. 1  will be explained in detail. The explanation will be made exemplifying the shift number setting unit  130   a  and the shift register unit  130   b.  Note that explanation of the shift number setting units  140   a  and  150   a  and the shift register units  140   b,    150   b  is the same as that of the shift number setting unit  130   a  and the shift register unit  130   b.    
         [0063]      FIG. 3  is a view explaining the shift number setting unit and the shift register unit according to Embodiment 1. As shown in  FIG. 3 , the shift number setting unit and the shift register unit have a shift register  30 , AND circuits  31  to  34 , an OR circuit  35 , and pull-up resistors  36 ,  37 . 
         [0064]    Among them, the shift register  30  is a circuit for switching outputs B to E from Low to High in response to the pulse number of a pulse signal An output from the pulse signal generating circuit  120 . Note that the shift register  30  is connected to the AND circuits  31  to  34 , and the outputs B to E output from the shift register  30  are input to the AND circuits  31  to  34 , respectively. 
         [0065]    Specifically, the shift register  30  obtains the pulse signal A, switches the output B from Low to High in response to a first pulse, and switches the output C from Low to High in response to a second pulse. Further, the shift register  30  switches the output D from Low to High in response to a third pulse and switches the output E from Low to High in response to a fourth pulse. 
         [0066]    The AND circuits  31  to  34  are circuits having two input terminals and one output terminal and outputting High from the output terminal when signals input to the two input terminals become High. One of the input terminals of each of the AND circuits  31  to  34  is connected to GND or to any one of the pull-up resistors according to the first pulse number. 
         [0067]    How the AND circuits  31  to  34  are connected when the shift register unit  130   b  turns “ON” the ON/OFF terminal at the time the first pulse number is “3”, that is, the pulse number becomes “3” will be explained. 
         [0068]    The output B of the shift register  30  is connected to one of the input terminals of the AND circuit  31 , and the other input terminal is connected to GND. Further, the output terminal of the AND circuit  31  is connected to the OR circuit  35 . Since one of the input terminals of the AND circuit  31  is connected to GND, the AND circuit  31  outputs Low to the OR circuit  35  at all times. 
         [0069]    The output C of the shift register  30  is connected to one of the input terminals of the AND circuit  32 , and the other input terminal is connected to GND. Further, the output terminal of the AND circuit  31  is connected to the OR circuit  35 . Since one of the input terminals of the AND circuit  32  is connected to GND, the AND circuit  32  outputs Low to the OR circuit  35  at all times. 
         [0070]    The output D of the shift register  30  is connected to one of the input terminals of the AND circuit  33 , and the pull-up resistor  37  is connected to the other input terminal. Further, the output terminal of the AND circuit  33  is connected to the OR circuit  35 . Since one of the input terminals of the AND circuit  33  is connected to the pull-up resistor  37 , the input terminal connected to the pull-up resistor  37  becomes High at all times. Accordingly, the AND circuit  33  switches an output of the output terminal to High at the time the output D connected to the input terminal becomes High (at the time the pulse number becomes 3). 
         [0071]    The output E of the shift register  30  is connected to one of the input terminals of the AND circuit  34 , and the pull-up resistor  36  is connected to the other input terminal. Further, the output terminal of the AND circuit  34  is connected to the OR circuit  35 . Since one of the input terminals of the AND circuit  34  is connected to the pull-up resistor  36 , the input terminal connected to the pull-up resistor  36  becomes High at all times. Accordingly, the AND circuit  34  switches an output of the output terminal to High at the time the output E connected to the input terminal becomes High (at the time the pulse number becomes 4). 
         [0072]    The OR circuit  35  is a circuit connected to the output terminals of the AND circuits  31  to  34  and turning “ON” the ON/OFF terminal at the time the output of any of the AND circuits  31  to  34  becomes High. Note that, as shown in  FIG. 3 , when the AND circuits  31 ,  32  are connected to GND and the AND circuits  33 ,  34  are connected to the pull-up resistors  36 ,  37 , an output of the AND circuit  33  becomes High at the time the pulse number becomes “3”. When the output of the AND circuit  33  becomes High, the OR circuit  35  turns “ON” the ON/OFF terminal. 
         [0073]    The pull-up resistors  36 ,  37  are resistors for keeping signal lines connected to the input terminals of the AND circuits  33 ,  34  in a High state. 
         [0074]    Next, operation waveforms of the pulse signal generating circuit  120 , the shift register  30 , the AND circuits  31  to  34 , and the OR circuit  35  shown in  FIG. 3  will be explained.  FIG. 4  is a view illustrating the operation waveforms of the pulse signal generating circuit  120 , the shift register  30 , the AND circuits  31  to  34 , and the OR circuit  35 . 
         [0075]    As shown in  FIG. 4 , the outputs from the AND circuits  31 ,  32  become Low at all times regardless of a pulse number of the pulse signal output from the pulse signal generating circuit  120  to the shift register  30  (refer to outputs J, K of the AND circuit of  FIG. 4 ). 
         [0076]    In contrast, the output D of the shift register  30  becomes High at the time the pulse number input to the shift register  30  becomes “3” (refer to the output B of the shift register of  FIG. 4 ), and an output L of the AND circuit  33  becomes High (refer to the output L of the AND circuit of  FIG. 4 ). Then, the output of the OR circuit  35  becomes High by that the output L of the AND circuit  33  becomes High (refer to an output N of the OR circuit of  FIG. 4 ). 
         [0077]    As shown in  FIG. 3 , a signal can be output after an arbitrary pulse number by setting ones of the inputs of the AND circuits  31  to  34  to Low or High. When, for example, a signal is output in response to the second pulse unlike  FIG. 3 , it is preferable to connect Low (GND) to one of the input terminals of the AND circuit  31  and to connect High (one of the pull-up resistors) to one of the input terminals of the AND circuits  32  to  34 . 
         [0078]    Further, in the case shown in  FIG. 3 , pulses up to the fourth pulse are treated using the shift register  30  and the four AND circuits  31  to  34 . However, when the number of the shift register and the AND circuits is increased, a pulse having any arbitrary number can be treated. Further, in  FIG. 3 , a timing at which the ON/OFF terminal is controlled by connecting the pull-up resistors  36 ,  37  and GND to the AND circuits  31  to  34 , but the embodiment is not limited thereto. A circuit, which outputs Low or High to the input terminals of the AND circuits  31  to  34  in response to, for example, a rewritable storage element and an external control signal, may be provided. 
         [0079]    As described above, the power supply control apparatus  100  according to Embodiment 1 controls a power supply to the load circuit  160  by connecting the one control signal wire from the pulse signal generating circuit  120  to the DC-DC converters  130  to  150 , which adjust a timing at which a voltage is output by counting a pulse number of the pulse signal generated by the pulse signal generating circuit  120 . As a result, a complex sequence control can be provided even in a highly dense wiring substrate without pressing other signal wires and thus a power supply circuit can be mounted on a device having more dense wires. 
         [0080]    In a conventional voltage monitor circuit and a conventional delay signal circuit, since setting of a sequence is changed by a configuration of a load circuit, the number of components increases because the sequence preferably be variously set, and thus a sequence setting cost and a manufacture management cost become expensive. However, in the power supply control apparatus  100  of Embodiment 1 according to the invention, since a sequence can be set only by setting a pulse number by a logic circuit, even if a configuration of a load circuit changes, the change of the configuration of the load circuit can be coped with by logically changing a pulse being set by the same circuit, and thus a design manpower cost and a manufacture management cost can be reduced. 
         [0081]    In the power supply control apparatus  100  according to Embodiment 1, a start-up sequence can be arbitrarily changed only by changing setting of a control circuit without switching a destination of connection of a control line. As a result, the start-up sequence can be changed by simply changing setting without modifying a wiring substrate. 
       Embodiment 2 
       [0082]    Next, a power supply control apparatus according to Embodiment 2 will be explained. The power supply control apparatus according to Embodiment 2 has a plurality of one-shot pulse generators for outputting single pulse signals in place of the pulse signal generating circuit  120  of the power supply control apparatus  100  shown in Embodiment 1, and respective DC-DC converters control a power supply sequence by adjusting a timing at which they output power based on the number of one-shot pulses output from the one-shot pulse generators. 
         [0083]    Next, a configuration of the power supply control apparatus according to Embodiment 2 will be explained.  FIG. 5  is a view illustrating a configuration of the power supply control apparatus according to Embodiment 2. As shown in  FIG. 5 , the power supply control apparatus  200  has an input supply power source  210 , voltage monitoring circuits  220   a  to  220   c,  one-shot pulse generators  230   a  to  230   c,  DC-DC converters  240  to  260 , and a load circuit  270 . 
         [0084]    The input supply power source  210  is a circuit for supplying a voltage to the DC-DC converters  240  to  260 . A plus terminal of the input supply power source  210  is connected to Vin (+) of each of the DC-DC converters  240  to  260 , and a minus terminal of the input supply power source  210  is connected to Vin (−) of each of the DC-DC converters  240  to  260 . A voltage supplied from the input supply power source  210  to the DC-DC converters  240  to  260  is shown by Vin. 
         [0085]    The voltage monitoring circuit  220   a  is a circuit for outputting a control signal to the one-shot pulse generator  230   a  when it detects Vin output from the input supply power source  210 . The voltage monitoring circuit  220   b  is a circuit for outputting a control signal to the one-shot pulse generator  230   b  when it detects Vout  1  output from the DC-DC converter  240 . The voltage monitoring circuit  220   c  is a circuit for outputting a control signal to the one-shot pulse generator  230   c  when it detects Vout  2  output from the DC-DC converter  250 . 
         [0086]    The one-shot pulse generator  230   a  is a circuit for outputting one pulse to the DC-DC converters  240  to  260  when it obtains the control signal from the voltage monitoring circuit  220   a.  The one-shot pulse generator  230   b  is a circuit for outputting one pulse to the DC-DC converters  240  to  260  when it obtains the control signal from the voltage monitoring circuit  220   b.  The one-shot pulse generator  230   c  is a circuit for outputting one pulse to the DC-DC converters  240  to  260  when it obtains the control signal from the voltage monitoring circuit  220   c.  In Embodiment 2, a pulse signal composed of one pulse is shown as a one-shot pulse. 
         [0087]    The DC-DC converter  240  is a circuit for obtaining one-shot pulses from the one-shot pulse generators  230   a  to  230   c  and outputting the voltage Vout  1  to the load circuit  270  when a sum total of the obtained one-shot pulses reach a predetermined number. Specifically, the DC-DC converter  240  has a shift number setting unit  240   a  and a shift register unit  240   b.  Note that the DC-DC converter  240  has Vin (+), Vin (−), Vout (+), Vout (−), and ON/OFF terminals as terminals. 
         [0088]    The shift number setting unit  240   a  is a circuit for setting a pulse number of a pulse signal acting as a timing at which Vout  1  is output. In the following explanation, the pulse number set by the shift number setting unit  240   a  is shown as a first pulse number. 
         [0089]    The shift register unit  240   b  is a circuit for counting the pulse number of the one-shot pulses output from the one-shot pulse generators  230   a  to  230   c  and turning “ON” the ON/OFF terminals when the counted pulse number reaches the first pulse number. When the ON/OFF terminal of the DC-DC converter  240  is turned “ON” in a state that Vin is applied thereto from the input supply power source  210 , the DC-DC converter  240  outputs the voltage Vout  1  to the load circuit  270 . 
         [0090]    The DC-DC converters  250  is a circuit for obtaining one-shot pulses from the one-shot pulse generators  230   a  to  230   c  and outputting a voltage Vout  2  to the load circuit  270  when a sum total of the obtained one-shot pulses reach a predetermined number. Specifically, the DC-DC converter  250  has a shift number setting unit  250   a  and a shift register unit  250   b.  Note that the DC-DC converter  250  has Vin (+), Vin (−), Vout (+), Vout (−), and ON/OFF terminals as terminals. 
         [0091]    The shift number setting unit  250   a  is a circuit for setting a pulse number of a pulse signal acting as a timing at which Vout  2  is output. In the following explanation, the pulse number set by the shift number setting unit  250   a  is shown as a second pulse number. 
         [0092]    The shift register unit  250  is a circuit for counting a pulse number of the one-shot pulses output from the one-shot pulse generators  230   a  to  230   c  and turning “ON” the ON/OFF terminals when the counted pulse number reaches the second pulse number. When the ON/OFF terminal of the DC-DC converter  250  is turned “ON” in a state that Vin is applied thereto from the input supply power source  210 , the DC-DC converter  250  outputs the voltage Vout  2  to the load circuit  270 . 
         [0093]    The DC-DC converter  260  is a circuit for obtaining one-shot pulses from the one-shot pulse generators  230   a  to  230   c  and outputting a voltage Vout  3  to the load circuit  270  when a sum total of the obtained one-shot pulses reach a predetermined number. Specifically, the DC-DC converter  260  has a shift number setting unit  260   a  and a shift register unit  260   b.  Note that the DC-DC converter  260  has Vin (+), Vin (−), Vout (+), Vout (−), and ON/OFF terminals as terminals. 
         [0094]    The shift number setting unit  260   a  is a circuit for setting a pulse number of a pulse signal acting as a timing at which Vout  3  is output. In the following explanation, the pulse number set by the shift number setting unit  260  is shown as a third pulse number. 
         [0095]    The shift register unit  260   b  is a circuit for counting a pulse number of the one-shot pulses output from the one-shot pulse generators  230   a  to  230   c  and turning “ON” the ON/OFF terminal when the counted pulse number reaches the third pulse number. When the ON/OFF terminal of the DC-DC converter  260  is turned “ON” in a state that Vin is applied thereto from the input supply power source  210 , the DC-DC converter  260  outputs the voltage Vout  3  to the load circuit  270 . 
         [0096]    The load circuit  270  is a circuit for executing various processes making use of the voltages sequentially supplied from the DC-DC converters  240  to  260 . A core circuit, an IO circuit, and various LSIs, for example, are mounted on the load circuit  270 . 
         [0097]    It is preferable to adjust a first pulse number, a second pulse number, and a third pulse number set to the shift register units  240   b  to  260   b  according to a power supply sequence of the voltages Vout  1  to  3  to adjust the power supply sequence of the voltages Vout  1  to  3  supplied to the load circuit  270 . When, for example, the voltages Vout  1 , Vout  2 , and Vout  3  are sequentially supplied to the load circuit  270  in this order, the first, second, and third pulse numbers may be sufficiently adjusted such that first pulse number&lt;second pulse number&lt;third pulse number. 
         [0098]    Note that detailed explanation of the shift number setting units  240   a  to  260   a  and the shift register units  240   b  to  260   b  shown in  FIG. 5  are the same as that of the shift number setting units  130   a  to  150   a  and the shift register units  130   b  to  150   b  shown in Embodiment 1 (refer to  FIG. 3 ). 
         [0099]    Next, an operation waveform of the power supply control apparatus  200  shown in  FIG. 5  will be explained.  FIG. 6  is a view illustrating the operation waveform of the power supply control apparatus  200  according to Embodiment 2. Note that the first pulse number of the shift register unit  240   b  is set to “1”, the second pulse number of the shift register unit  250   b  is set to “2”, and the third pulse number of the shift register unit  260   b  is set to “3” as an example. 
         [0100]    When the input supply power source  210  supplies Vin to the DC-DC converters  240  to  260  (refer to Vin of  FIG. 6 ), the voltage monitoring circuit  220   a  detects Vin and outputs a control signal to the one-shot pulse generator  230   a  which in turn outputs one-shot pulses to the DC-DC converters  240  to  260  (refer to V 0  of  FIG. 6 ). 
         [0101]    The shift register unit  240   b  obtains the one-shot pulse output from the one-shot pulse generator  230   a  and outputs a control signal S 1  to the ON/OFF terminal when a pulse number becomes “1” (refer to S 1  of  FIG. 6 ) to thereby turn “ON” the ON/OFF terminal. When the ON/OFF terminal is turned “ON”, the DC-DC converter  240  outputs Vout  1  (refer to Vout  1  of  FIG. 6 ). 
         [0102]    The voltage monitoring circuit  220   b  detects Vout  1  and outputs a control signal to the one-shot pulse generator  230   b  which in turn outputs one-shot pulses to the DC-DC converters  240  to  260  (refer to V 1  of  FIG. 6 ; one-shot pulse is output from the one-shot pulse generator  230   a  with a delay Ts). 
         [0103]    The shift register unit  250   b  obtains the one-shot pulse output from the one-shot pulse generator  230   b  and outputs a control signal S 2  to the ON/OFF terminal when a pulse number becomes “2” (refer to S 2  of  FIG. 6 ) to thereby turn “ON” the ON/OFF terminal. When the ON/OFF terminal is turned “ON”, the DC-DC converter  250  outputs Vout  2  (refer to Vout  2  of  FIG. 6 ). 
         [0104]    The voltage monitoring circuit  220   c  detects Vout  2  and outputs a control signal to the one-shot pulse generator  230   c  which in turn outputs one-shot pulses to the DC-DC converters  240  to  260  (refer to V 2  of  FIG. 6 ; one-shot pulse is output from the one-shot pulse generator  230   b  with a delay Ts). 
         [0105]    The shift register unit  260   b  obtains the one-shot pulse output from the one-shot pulse generator  230   c  and outputs a control signal S 3  to the ON/OFF terminal when a pulse number becomes “3” (refer to S 3  of  FIG. 6 ) to thereby turn “ON” the ON/OFF terminal. When the ON/OFF terminal is turned “ON”, the DC-DC converter  260  outputs Vout  3  (refer to Vout  3  of  FIG. 6 ). 
         [0106]    As described above, the power supply control apparatus  200  according to Embodiment 2 has the one-shot pulse generators for outputting single pulse signals in place of the pulse signal generating circuit and controls power supplied to the load circuit  270  by that the DC-DC converters  240  to  260  count the one-shot pulses output from the one-shot pulse generators  230   a  to  230   c  and control a timing at which a voltage is output. As a result, a power supply sequence can be accurately controlled by suppressing an adverse effect due to a disturbance, a delay and the like of a pulse signal. 
         [0107]    In a conventional voltage monitoring circuit and a conventional delay signal circuit, since setting of a sequence is changed depending on a configuration of a load circuit, many types of settings are demanded to change and the number of components for setting constants for this purpose increases, resulting in an increase of a setting process cost and a manufacture management cost. However, in the power supply control apparatus  200  of the invention, since a sequence can be set only by setting a pulse number by a logic circuit, even if a configuration of a load circuit changes, the change can be coped with only by changing setting of a pulse by the same circuit. Accordingly, the invention can reduce a design manpower cost and a manufacture management cost. 
         [0108]    In the power supply control apparatus  200  according to embodiment 2, a start-up sequence can be arbitrarily changed only by changing setting of a control circuit without switching a destination of connection of a control line. As a result, the start-up sequence can be changed by simply changing setting without modifying a wiring substrate. 
         [0109]    All examples and conditional language recited herein are intended for pedagogical purposes to aid the reader in understanding the invention and the concepts contributed by the inventor to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions, nor does the organization of such examples in the specification relate to a showing of the superiority and inferiority of the invention. Although the embodiments of the present inventions have been described in detail, it should be understood that the various changes, substitutions, and alterations could be made hereto without departing from the spirit and scope of the invention.