Abstract:
The invention proposes a low-dropout voltage regulator comprising an output terminal for providing an output voltage (V out ) regulated as a function of a reference voltage, and for providing an output current (I out ), and additionally comprising an output current limiting unit (LIMIT 3 ), with said unit comprising:
       replication means for replicating the output current (T 31 ) to provide a mirror current of the output current (I mirror ),   comparison means (COMP 31,  COMP 32 ) for comparing the mirror current with a reference current (I ref ),   feedback means for supplying feedback (COMP 31,  COMP 32,  R 35 , REGUL 3 ) to the regulator in order to limit the output current when the mirror current is greater than the reference current,
 
and the mirror current is injected into the output terminal.

Description:
[0001]    This application is a continuation of prior U.S. patent application Ser. No. 13/383941, filed 13 Jan. 2012, which was the National Stage of International Application No. PCT/EP2010/060263, filed 15 Jul. 2010, which claims the benefit from International Application FR 0954924, filed 16 Jul. 2009, the disclosures of all of which are incorporated by reference herein in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to Low-Dropout (LDO) voltage regulator circuits. 
         [0003]    More particularly it concerns the limiting of short circuit current in such regulators. 
       TECHNOLOGICAL BACKGROUND 
       [0004]    An LDO regulator allows providing a stable output voltage in spite of fluctuations in the general supply voltage of the circuit in which it is installed. 
         [0005]    When a circuit containing an LDO regulator is powered up, or when there is an accidental short circuit of the regulator output, it is necessary to limit the output current to avoid malfunctions. 
         [0006]    In order to limit this short circuit current, one can consider the use of dedicated current-limiting circuits. These circuits would consist of a feedback loop which measures the output current of the regulator, then compares it to a reference current in order to act on the regulator when the output current becomes greater than the reference current. 
         [0007]    Such a current-limiting circuit is shown in  FIG. 1 . 
         [0008]    In this circuit, one can see two particular functional units. The first unit REGUL 1  represents the voltage regulating loop of the regulator. This regulating loop allows maintaining a stable output voltage V out . The second unit LIMIT 1  represents the current-limiting loop. 
         [0009]    In what follows, only the current-limiting loop is considered. A person skilled in the art is able to understand the operation of the regulating loop when reading the circuit. 
         [0010]    In order to access the output current I out , a PMOS copy transistor T 10  is arranged such that it copies the output current issuing from the PMOS power transistor T 11 . 
         [0011]    In order to simplify the presentation, the current from the transistor T 11  is included in the output current. The current drawn by the resistors of the regulating loop is negligible compared to the current issuing from the transistor. 
         [0012]    The transistors T 10  and T 11  are paired transistors on silicon and are arranged such that the gate of T 10  is connected to the gate of T 11 , and the source of T 10  is connected to the source of T 11 . 
         [0013]    Thus the drain current I mirror  of the transistor T 10  is proportional to the drain current I out  of the transistor T 11 . 
         [0014]    The transistors T 10  and T 11  have the same physical properties. In particular, they have the same gate length L. However, they have different gate widths W 10  and W 11 . In fact, the width W 11  of the gate of T 11  is much greater than the width W 10  of the gate of T 10 . 
         [0015]    Thus by using the linear model for MOS transistors, we have: 
         [0000]    
       
         
           
             
               I 
               out 
             
             = 
             
               
                 
                   W 
                   11 
                 
                 
                   W 
                   10 
                 
               
               . 
               
                 I 
                 mirror 
               
               . 
             
           
         
       
     
         [0016]    The drain of the transistor T 10  is coupled to the non-inverting input of a comparator COMP 1  as well as to a resistor R 10 . The inverting input of the comparator is coupled to a reference current source I ref  in parallel with a second resistor R 11 . The two resistors R 10  and R 11  each have a grounded end. For example, they have the same R value. 
         [0017]    Thus the output V s10  of the comparator COMP 1  is a voltage proportional to the difference between the current I mirror  (which is proportional to the output current I out ) and the reference current Iref. The coefficient of proportionality is the product of the resistor R and the gain G 10  of the comparator. 
         [0018]    The output from the comparator is coupled to the gates of the PMOS transistors T 10  and T 11 . Thus, using the small signal model, the current I out  is proportional to the voltage output from the comparator, with the coefficient of proportionality being the gain G mp  of the transistor T 11 . 
         [0019]    One can therefore model the signals in the following manner: 
         [0000]        V   s10   =G   10   .R. ( I   mirror   −I   ref ) 
         [0000]      I out =−G mp V s10 .
 
         [0020]    Lastly one can express I out  as a function of I ref , using: 
         [0000]    
       
         
           
             
               I 
               out 
             
             = 
             
               
                 
                   W 
                   11 
                 
                 
                   W 
                   10 
                 
               
                
               
                 
                   
                     
                       G 
                       mp 
                     
                     . 
                     
                       G 
                       10 
                     
                     . 
                     R 
                   
                   
                     
                       
                         G 
                         mp 
                       
                       . 
                       
                         G 
                         10 
                       
                       . 
                       R 
                     
                     + 
                     1 
                   
                 
                 . 
                 
                   I 
                   ref 
                 
                 . 
               
             
           
         
       
     
         [0021]    As the open-loop gain G mp .G 10 .R is very high, one can simplify the expression for I out  as follows: 
         [0000]    
       
         
           
             
               I 
               out 
             
             = 
             
               
                 
                   W 
                   11 
                 
                 
                   W 
                   10 
                 
               
               . 
               
                 I 
                 ref 
               
               . 
             
           
         
       
     
         [0022]    One can therefore see that it is possible to set the output current, through the choice of the values for I ref  and W 10 . 
         [0023]    The current consumption is very high in this current-limiting loop. In addition, this consumption grows even greater as the size of the power transistor T 11  decreases. 
         [0024]    A few values are given below to illustrate this. 
         [0000]    
       
         
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
             
             
               
                 Current consumed by the comparator COMP1 
                 I ad  = 4 μA 
               
               
                 Output current 
                 I out  = 200 mA 
               
               
                 Reference current 
                 I ref  = 1 μA 
               
               
                 Width of gate of transistor T11 
                 W 11  = 32 000 μm 
               
               
                 Width of gate of transistor T10 
                 W 10  = 10 μm 
               
               
                 Length of gate of transistors T 10  and T 11   
                 L = 0.2 μm 
               
               
                   
               
             
          
         
       
     
         [0025]    The current I q  consumed by the current-limiting loop can be approximated by adding the reference current, the mirror current, and the current consumed by the comparator: 
         [0000]    
       
      
       I 
       q 
       =I 
       ref 
       +I 
       ad 
       +I 
       mirror  
      
     
         [0026]    which is: 
         [0000]    
       
         
           
             
               I 
               q 
             
             = 
             
               
                 I 
                 ref 
               
               + 
               
                 I 
                 ad 
               
               + 
               
                 
                   
                     W 
                     10 
                   
                   
                     W 
                     11 
                   
                 
                  
                 
                   
                     I 
                     0 
                   
                   . 
                 
               
             
           
         
       
     
         [0027]    Using the numbers in the above table, one obtains a current I q =67.5 μA. 
         [0028]    The specifications for LDO regulators impose a current consumption of less than 150 μA. The current-limiting loop therefore already consumes close to half of the objective. 
         [0029]    In order to reduce this consumption, one can reduce W 10 . However, the topography of the circuit does not allow much reduction in this parameter. One can also consider increasing W 11 . However, there is almost no room for adjustment here because the output current depends on W 11 . 
         [0030]    In addition, the accuracy of the current-limiting loop is very low because the pairing of the transistors T 10  and T 11  is made difficult by their difference in surface area which can have a ratio as high as 2000 or more. 
         [0031]      FIG. 2  illustrates the topography of these transistors in the LDO circuit. One can see that it is difficult to pair these two transistors because almost the entire surface area of the silicon is occupied by T 11 . 
         [0032]    The precision of the current-limiting loop can be estimated in comparison to the accuracy of the copying of the current by the transistor T 10 . The standard deviation is calculated on the relative error in the recopying of the current, and the accuracy of the recopying is estimated as six times this standard deviation. Then the accuracy is expressed as: 
         [0000]    
       
         
           
             
               acc 
               = 
               
                 6. 
                  
                 
                   
                     
                       
                         4. 
                          
                         
                           
                             A 
                             vt 
                             2 
                           
                           
                             V 
                             gt 
                             2 
                           
                         
                       
                       + 
                       
                         A 
                         β 
                         2 
                       
                     
                     
                       2. 
                        
                       
                         
                           W 
                           10 
                         
                         . 
                         L 
                       
                     
                   
                 
               
             
             , 
           
         
       
     
         [0000]    where V gt : the difference in voltage between the gate and the source of the transistor T 10  on the one hand and the threshold voltage of the transistor on the other, and A vt  and A β : parameters of the circuit. 
         [0033]    The accuracy was calculated for several circuits with the same parameters and for different values of W 10 , L, and V gt . 
         [0034]    The results are presented in the following table. 
         [0000]    
       
         
               
               
               
               
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
               
                   
               
               
                 Circuit 
                 A vt (mV · μm)   
                 A β (% · μm)   
                 W 10 (μm)   
                 L (μm)   
                 V gt (mV)   
                 Acc 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 9.4 
                 0.032 
                 10 
                 0.6 
                 200 
                 0.24 
               
               
                 2 
                 9.4 
                 0.032 
                 15 
                 0.6 
                 367 
                 0.12 
               
               
                 3 
                 9.4 
                 0.032 
                 10 
                 0.6 
                 207 
                 0.23 
               
               
                 4 
                 9.4 
                 0.032 
                 5 
                 0.6 
                 434 
                 0.18 
               
               
                 5 
                 9.4 
                 0.032 
                 20 
                 0.6 
                 190 
                 0.23 
               
               
                 6 
                 9.4 
                 0.032 
                 10 
                 0.6 
                 180 
                 0.27 
               
               
                   
               
             
          
         
       
     
         [0035]    The accuracy ranges from 12% to 27%. This level of accuracy is low, and does not take into account the effects of temperature and voltage offsets. When such phenomena are taken into account, the result is an even lower accuracy. 
       SUMMARY 
       [0036]    Therefore a need exists for an LDO regulator comprising a current-limiting loop that offers good accuracy and has reduced current consumption. 
         [0037]    For this purpose, a low-dropout voltage regulator is proposed that comprises an output terminal for providing an output voltage regulated as a function of a reference voltage, and for providing an output current, and that additionally comprises an output current limiting unit. The unit comprises:
       replication means for replicating the output current to provide a mirror current of the output current,   comparison means for comparing the mirror current with a reference current,   feedback means for supplying feedback to the regulator in order to limit the output current when the mirror current is greater than the reference current. In addition, the mirror current is injected into the output terminal.       
 
         [0041]    In this manner the mirror current which is used for the purposes of measuring the output current is not consumed by the current-limiting unit. 
         [0042]    Advantageously, the invention proposes including this current in the output current. 
         [0043]    As a comparison, in the limiting loop described with reference to  FIG. 1 , the mirror current was drawn by the ground of the circuit, and was therefore completely consumed by the limiting loop. 
         [0044]    With a regulator of the invention, it is possible to save significant amounts of current, which facilitates the design of LDO regulators. The current consumption of the current-limiting loop constituted a very large part of the current consumed by regulators of the prior art. 
         [0045]    In addition, the regulator of the invention allows more precise limiting of the current. 
         [0046]    The current consumed by the current-limiting unit does not depend on a means of replicating the output current. Therefore, unlike the circuit in  FIG. 1 , the replication means do not introduce inaccuracy. 
         [0047]    In some embodiments, the reference current is injected into the output terminal. 
         [0048]    This allows further reduction of the current consumption. 
         [0049]    As a comparison, the reference current of the circuit in  FIG. 1  is drawn by the ground once it has traversed the resistor R 11 . It is therefore completely consumed by the current-limiting loop. 
         [0050]    In some embodiments, the comparison means comprises:
       a first input coupled to a first electric potential which is a function of the output voltage and the intensity of the mirror current, and   a second input coupled to a second electric potential which is a function of the output voltage and the intensity of the reference current.       
 
         [0053]    It is thus possible to compare the mirror current and the reference current by comparing the first and second potentials without drawing, and therefore consuming, said currents. 
         [0054]    According to some embodiments:
       the output terminal is the drain of a first PMOS power transistor,   the replication means of the output current comprises a second PMOS transistor paired with the first transistor, with the gate of the first transistor being connected to the gate of the second transistor and the source of the first transistor being connected to the source of the second transistor,   the output from the comparator is coupled to the gates of the first and second transistors.       
 
         [0058]    The regulator additionally comprises:
       a first resistor arranged between the output terminal and the first input of the comparator, and   a second resistor arranged between the output terminal and the second input of the comparator.       
 
         [0061]    In these embodiments it is possible to create replication (or copy) transistors that have a significant gate surface area. This facilitates pairing with the power transistor. 
         [0062]    In addition, in these embodiments, there is great flexibility in the choice of parameters that set the limit for the output current. 
         [0063]    The design of the regulator is therefore facilitated. 
         [0064]    The invention also provides for a method for controlling a regulator, a computer program comprising instructions for implementing the method, and a device comprising a regulator according to the invention. 
         [0065]    These objects present at least the same advantages as those provided by the regulator of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0066]    Other features and advantages of the invention will become apparent from the following description. This description is purely illustrative and is to be read in light of the attached drawings, in which, in addition to  FIGS. 1 and 2 : 
           [0067]      FIG. 3  illustrates an LDO regulator comprising a current-limiting loop according to an embodiment of the invention; 
           [0068]      FIG. 4  illustrates the gain in accuracy provided by a circuit according to an embodiment of the invention; 
           [0069]      FIG. 5  illustrates an embodiment of the comparators COMP 31  and COMP 32  of  FIG. 3   
           [0070]      FIG. 6  is a flow chart of the steps for implementing the method according to an embodiment of the invention, 
           [0071]      FIG. 7  is a device comprising a regulator according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0072]    A circuit according to an embodiment of the invention is described below, first with reference to  FIG. 3 . 
         [0073]    The circuit is represented in this figure, in which a regulating loop REGUL 3  and a current-limiting loop LIMIT 3  can be recognized. 
         [0074]    The regulating loop comprises two resistors in series R 31  and R 32  connecting the output voltage Vout to the ground. The node between the resistors R 31  and R 32  is coupled to the non-inverting input of a comparator COMP 33 . The inverting input of this comparator is coupled with a reference voltage source V ref . 
         [0075]    Thus the output voltage from the comparator COMP 33  is a linear combination of the output voltage Vout and the reference voltage Vref. This is equivalent to comparing the output voltage to a reference voltage Vref′ whose value is a function of the reference voltage Vref and the value of the resistors R 31  and R 32 . The output voltage of the comparator COMP 33  can be written as: 
         [0000]    
       
         
           
             
               
                 V 
                 
                   s 
                    
                   
                       
                   
                    
                   33 
                 
               
               = 
               
                 
                   G 
                   33 
                 
                 . 
                 
                   
                     R 
                      
                     
                         
                     
                      
                     31 
                   
                   
                     
                       R 
                        
                       
                           
                       
                        
                       31 
                     
                     + 
                     
                       R 
                        
                       
                           
                       
                        
                       32 
                     
                   
                 
                 . 
                 
                   ( 
                   
                     
                       V 
                       OUT 
                     
                     - 
                     
                       
                         
                           
                             R 
                              
                             
                                 
                             
                              
                             31 
                           
                           + 
                           
                             R 
                              
                             
                                 
                             
                              
                             32 
                           
                         
                         
                           R 
                            
                           
                               
                           
                            
                           31 
                         
                       
                       . 
                       
                         V 
                         ref 
                       
                     
                   
                   ) 
                 
               
             
             , 
           
         
       
     
         [0000]    where G 33  is the gain of the comparator COMP 33 . 
         [0076]    The output voltage of the comparator COMP 33  is coupled to the gate of a NMOS transistor T 32 . The drain of this transistor T 32  is connected to the ground and the source of this transistor is connected to the gates of transistors T 30  and T 31  described below. 
         [0077]    The current-limiting loop comprises a PMOS power transistor T 30 , and a PMOS copy transistor T 31 . 
         [0078]    The transistors T 30  and T 31  are paired on silicon and arranged such that the gate of T 30  is connected to the gate of T 31 , and the source of T 30  is connected to the source of T 31 . 
         [0079]    Thus the drain current I mirror of  the transistor T 31  is proportional to the drain current of the transistor T 30 . In order to simplify the presentation, the drain current of the transistor T 30  is considered to be equal to the output current I out . In fact, in practice, the other currents at the output node of the circuit are negligible compared to I out . 
         [0080]    The current I mirror  is not lost because it is injected into the output via a resistor R 33 . 
         [0081]    In addition, the reference current Iref used for the limiting loop is also injected into the output via a resistor R 34 . 
         [0082]    The limiting loop comprises two comparators COMP 31  and COMP 32 , associated such that the output of COMP 31  is connected to the output of COMP 32 , the inverting input of COMP 31  is connected to the inverting input of COMP 32 , and the non-inverting input of COMP 31  is connected to the non-inverting input of COMP 32 . 
         [0083]    Unlike the comparator COMP 1  of  FIG. 1 , the comparators COMP 31  and COMP 32  of  FIG. 3  do not use the ground as a reference. Their reference is the output voltage. As this voltage is variable and not always close to 0 (varying for example between 0 Volts and 3.3 Volts), a larger working range must be allowed for, which is what the association of the two comparators COMP 31  and COMP 32  does. 
         [0084]    They are additionally arranged such that when the value of the voltage Va between the ground and the inverting input of the comparators is less than half of the supply voltage Vdd it is the comparator COMP 31  which operates, and when this voltage Va is between Vdd/2 and Vdd, it is the comparator COMP 32  which operates. 
         [0085]    As will be clear to a person skilled in the art, the association of these two comparators is equivalent to one comparator. 
         [0086]    The outputs from comparators COMP 31  and COMP 32  are coupled to the gates of transistors T 30  and T 31  and to a resistor R 35  for switching between the regulating and current-limiting loops. The resistor R 35  connects the output of the comparators COMP 31  and COMP 32  to the supply voltage potential Vdd. 
         [0087]    In what follows, simplified calculations are used to illustrate the savings in current and the gain in accuracy realized by the circuit described above. 
         [0088]    The following notations are used: 
         [0089]    Vb: drain potential of the transistor T 31   
         [0090]    W 31 : Width of the gate of the transistor T 31   
         [0091]    W 30 : Width of the gate of the transistor T 30   
         [0092]    G mp30 : gain of the transistor T 30   
         [0093]    G 31 : gain of the comparator COMP 31   
         [0094]    G 32 : gain of the comparator COMP 32 . 
         [0095]    The transistors T 30  and T 31  have the same physical characteristics. In particular, they have the same gate length. Using the linear model for transistors, one obtains: 
         [0000]    
       
         
           
             
               I 
               mirror 
             
             = 
             
               
                 
                   W 
                   31 
                 
                 
                   W 
                   30 
                 
               
               . 
               
                 I 
                 out 
               
               . 
             
           
         
       
     
         [0096]    In addition: 
         [0000]        V   a   =V   out   +R   34   .I   ref , and 
         [0000]        Vb=V   out   +R   33   .I   mirror , or 
         [0000]    
       
         
           
             Vb 
             = 
             
               
                 V 
                 out 
               
               + 
               
                 
                   R 
                   33 
                 
                 . 
                 
                   
                     W 
                     31 
                   
                   
                     W 
                     30 
                   
                 
                 . 
                 
                   I 
                   out 
                 
                 . 
               
             
           
         
       
     
         [0097]    When 
         [0000]    
       
         
           
             
               
                 
                   V 
                   dd 
                 
                 2 
               
               ≤ 
               
                 V 
                 a 
               
               ≤ 
               
                 V 
                 dd 
               
             
             , 
           
         
       
     
         [0000]    the comparator COMP 31  operates and one obtains: 
         [0000]        Vs=G   31 .( V   b   −V   a ) 
         [0000]    
       
         
           
             
               V 
               s 
             
             = 
             
               - 
               
                 
                   
                     I 
                     OUT 
                   
                   
                     G 
                     
                       mp 
                        
                       
                           
                       
                        
                       30 
                     
                   
                 
                 . 
               
             
           
         
       
     
         [0098]    Which leads to: 
         [0000]    
       
         
           
             
               
                 G 
                 31 
               
               . 
               
                 ( 
                 
                   
                     
                       R 
                       2 
                     
                      
                     
                       
                         
                           W 
                           31 
                         
                         
                           W 
                           30 
                         
                       
                       . 
                       
                         I 
                         OUT 
                       
                     
                   
                   - 
                   
                     
                       R 
                       34 
                     
                     . 
                     
                       I 
                       ref 
                     
                   
                 
                 ) 
               
             
             = 
             
               - 
               
                 
                   
                     I 
                     OUT 
                   
                   
                     G 
                     
                       mp 
                        
                       
                           
                       
                        
                       30 
                     
                   
                 
                 . 
               
             
           
         
       
     
         [0099]    After simplification one obtains: 
         [0000]    
       
         
           
             
               I 
               out 
             
             = 
             
               
                 
                   
                     R 
                     33 
                   
                   . 
                   
                     G 
                     31 
                   
                   . 
                   
                     G 
                     
                       mp 
                        
                       
                           
                       
                        
                       30 
                     
                   
                 
                 
                   1 
                   + 
                   
                     
                       R 
                       33 
                     
                     . 
                     
                       G 
                       31 
                     
                     . 
                     
                       G 
                       
                         mp 
                          
                         
                             
                         
                          
                         30 
                       
                     
                   
                 
               
               . 
               
                 
                   W 
                   30 
                 
                 
                   W 
                   31 
                 
               
               . 
               
                 
                   R 
                   34 
                 
                 
                   R 
                   33 
                 
               
               . 
               
                 I 
                 ref 
               
               . 
             
           
         
       
     
         [0100]    As the open-loop gain R 33 .G 31 .G mp30  is very high, one arrives at the following approximation: 
         [0000]    
       
         
           
             
               I 
               out 
             
             = 
             
               
                 
                   W 
                   30 
                 
                 
                   W 
                   31 
                 
               
               . 
               
                 
                   R 
                   34 
                 
                 
                   R 
                   33 
                 
               
               . 
               
                 I 
                 ref 
               
               . 
             
           
         
       
     
         [0101]    When 
         [0000]    
       
         
           
             
               0 
               ≤ 
               
                 V 
                 a 
               
               ≤ 
               
                 
                   V 
                   dd 
                 
                 2 
               
             
             , 
           
         
       
     
         [0000]    the comparator COMP 32  operates, and with the same type of reasoning as for the above case, the same result is reached. 
         [0102]    One can see that there is a set of three parameters W 31 , R 33 , R 34  for setting the output current. 
         [0103]    In the current-limiting loop LIMIT 3 , the current consumed corresponds to the current consumed by the comparators COMP 31  and COMP 32 . If these currents are considered to be equal, and comparable to the current consumed by the comparator COMP 1  of  FIG. 1 , a savings of current corresponding to is 
         [0000]    
       
         
           
             
               I 
               ref 
             
             - 
             
               I 
               ad 
             
             + 
             
               
                 
                   W 
                   10 
                 
                 
                   W 
                   11 
                 
               
                
               
                 I 
                 0 
               
             
           
         
       
     
         [0000]    observed. Applying the numbers from Table 1, a consumption of 8 μA is found. This current consumption is to be compared with the 67.5 μA of the circuit in  FIG. 1 . A clear savings in current consumption is found. 
         [0104]    In addition, in this solution, the current consumed no longer depends on the width of the transistors T 30  and T 31  (only the currents of the comparators are consumed). It is therefore possible to increase the surface area of the gate of the transistor T 31  which improves its pairing with the transistor T 30 , and which therefore improves the accuracy of the current loop. In fact, the accuracy of the copy transistor is inversely proportional to the square root of the surface area of this transistor (see the expression for acc given above). 
         [0105]      FIG. 4  illustrates the accuracy of circuits according to  FIG. 1  as curve A, and the accuracy of circuits according to embodiments of the invention as curve B. 
         [0106]    For a same short-circuit current limit value I 0 , the y axis plots the number of circuits offering effective limiting to a given current limit value. 
         [0107]    The distribution of circuits is Gaussian, centered around I 0 . One can see that for circuits according to embodiments of the invention, the Gaussian curve is more narrow, which clearly illustrates the gain in accuracy in comparison to the limiting loops of  FIG. 1 . 
         [0108]      FIG. 5  illustrates an embodiment of the comparators COMP 31  and COMP 32  described above with reference to  FIG. 3 . 
         [0109]    The comparators are operational amplifiers. The comparator COMP 32  operates for low voltages, and the comparator COMP 31  operates for high voltages. 
         [0110]    V s  represents their common output, V− their common inverting input, and V+ their common non-inverting input. 
         [0111]    A method for controlling a regulator is described with reference to  FIG. 6 . First the current I mirror is  generated during a step of copying the output current S 60 . The mirror current is then compared to the reference current during the step S 61 . If during the step T 62  it is determined that the mirror current is greater than the reference current, a means of supplying feedback to the regulator is brought into play during the step S 63  in order to limit the output current. 
         [0112]    Lastly, in a final step S 64 , the mirror current is injected into the regulator output. During this step, the reference current can also be injected. 
         [0113]    A computer program comprising instructions for implementing the method can be deduced from the general flowchart in  FIG. 6 . 
         [0114]    A device is described with reference to  FIG. 7 , comprising a regulator of the invention. This device can be of various types. In fact it can be any device in which an LDO regulator is used. 
         [0115]    In this device DEV, there is a memory MEM, in particular for storing a computer program according to the invention, a processor PROC for implementing this program, a regulator REGUL, and a unit CIRC to which is supplied the regulated voltage provided by the regulator. The regulator comprises a regulating unit M REG  and an output current limiting unit M LIM . 
         [0116]    Of course, the invention is not limited to the embodiments described above. It extends to all equivalent variations.