Abstract: Circuits and methods are provided for generating reference currents. In one implementation, a circuit is provided that includes a first source and a current control circuit in communication with the first source. The first source generates a first reference current that is a ratio of a first reference voltage and an external resistance. The current control circuit produces a second reference current that is a ratio of a second reference voltage and the external resistance. The current control circuit produces the second reference current without being directly coupled to the external resistance.

Abstract: A current generator, including a chopper stabilization operational amplifier, a transistor, and an impedance unit is provided. The chopper stabilization operational amplifier includes a first input terminal, a second input terminal, and an output terminal. The transistor includes a gate coupled to the output terminal of the chopper stabilization operational amplifier, a first source/drain coupled to the first input terminal of the chopper stabilization operational amplifier, and a second source/drain serving as a current output terminal of the current generator. The impedance unit includes a first terminal coupled to the first source/drain of the transistor, and a second terminal coupled to a first voltage.

Abstract: A low noise voltage reference circuit is described. The reference circuit utilizes a bandgap reference component and may include at least one of a current shunt or filter to reduce high and low noise contributions to the output. Further modifications may include a curvature correction component.

Abstract: A dynamic bias control circuit includes a current source, a first switch, a differential amplifier, and a third switch. The current source outputs a first current. The first switch is coupled to an output end of the current source for generating the first current. The differential amplifier includes a first input end for receiving a reference voltage and a second input end coupled to the first switch. The third switch is coupled to an output end of the differential amplifier and to the first end of the first switch for adjusting a voltage at the first end of the first switch according to a result outputted from the differential amplifier. A control end of the first switch is coupled to a second switch. The second switch is used for inputting a second current into the second switch, wherein the second current to the first current is a predetermined ratio.

Abstract: An electronic device has an LDO regulator for varying loads. The LDO regulator includes a primary supply node coupled to a primary voltage supply. An output node provides a secondary supply voltage and a load current. A bias current source generates a bias current. A gain stage coupled to the bias current source increases the maximum available load current. The gain stage includes a first MOS transistor biased in weak inversion coupled to a current mirror which mirrors the drain current through the first MOS transistor to the output node. The gate-source voltage of the first MOS transistor increases in response to a decreasing secondary supply voltage level at the output node to increase the available load current.

Abstract: A linear regulator for outputting a regulated voltage with improved rejection of high frequency components in the power supply. The linear regulator includes an op-amp connected in a linear feedback loop to drive first and second current legs based on a voltage reference. An output driver includes a load capacitance across which the regulated voltage is output, and further includes a ratio-driven current mirror having a mirror ratio defined by relative sizes of active devices in the first and second current legs, as compared with relative sizes of active devices in the output driver. Because the output driver and its load capacitance are provided outside the linear feedback loop, large values for the load capacitance can be selected without destabilization of the feedback loop. Thus, the value of the load capacitance can be chosen at any value according to frequency rejection requirements.

Abstract: A temperature corrected voltage bandgap circuit is provided. The circuit includes first and second diode connected transistors. A first switched current source is coupled to the one transistor to inject or remove a first current into or from the emitter of that transistor. The first current is selected to correct for curvature in the output voltage of the bandgap circuit at one of hotter or colder temperatures.

Abstract: Bandgap reference (BGR) circuits and methods are described herein for providing high accuracy, low power Bandgap operation when using small, low voltage devices in the analog blocks of the BGR circuit. In some cases, chopped input stabilization and dynamic current matching techniques may be combined to compensate for input voltage offsets in the operational amplifier portion and current offsets in the current mirror portion of the Bandgap circuit. When used together, the chopped stabilization and dynamic current matching techniques provide a significant increase in accuracy, especially when using small, low voltage devices in the analog blocks to reduce layout area and support low power supply operation (e.g., power supply values down to about 1.4 volts and below).

Abstract: A constant-current circuit includes a first transistor for supplying a current based on a control signal input to a gate of the first transistor so as to serve as a current source, a second transistor for supplying a current to a load based on the control signal input to a gate of the second transistor, a voltage regulation unit for controlling a drain voltage of the first transistor according to a drain voltage of the second transistor, a current detector for detecting a value of a current flowing through the first transistor and output a current according to the detected value, and a controller for controlling each gate voltage of the first and second transistors according to the value detected by the current detector so that the current flowing through the first transistor becomes a predetermined value. The first and second transistors are MOS transistors having the same conductivity.

Abstract: This disclosure relates to a compensating for nonlinearity resulting from a capacitance feedback in current cells of a single ended digital to analog circuit.

Abstract: A bandgap voltage reference circuit includes a bandgap voltage generation circuit that can produce a bandgap reference voltage in response to an activation voltage signal, a start-up circuit that can produce the activation voltage signal in response to one-shot voltage pulse and an one-shot pulse generator circuit configured to produce the one-shot voltage pulse. The start-up circuit can be automatically shut off after the one-shot voltage pulse.

Abstract: A current detector circuit for detecting a load current flowing through a load includes a first series circuit having a first element and the load connected in series, a second series circuit having a second element and a resistor connected in series, the second element having a temperature characteristic equal to the temperature characteristic of the resistance of the first element, a power supply configured to supply voltage to the first series circuit and the second series circuit, and a control circuit configured to control the voltage drop across the second element so that the voltage drop across the second element is equal to the voltage drop across the first element. A current detection signal corresponding to the load current is generated based on a current flowing through the second element.

Abstract: Inventive embodiments described here provide for accurately distributing a voltage reference to multiple cores of an integrated circuit (IC). A quasi-differential interface is used to transmit the voltage reference, and a virtual ground is established at a receiver located at each core location on the integrated circuit. In one embodiment, the receiver is an operational transconductance amplifier (OTA) that converts a virtual-ground-referenced voltage input to a current. In one embodiment, the OTA converts the virtual-ground-referenced voltage into three currents via three driving current sources operating relative to the virtual ground and the local ground of the core. Negative feedback controls the accuracy of this conversion and provides a way to cancel the effects of the distribution resistance. The current is sourced across the voltage domains between the virtual ground and the VSS, which is the IC ground. An I*R drop across a resistor converts the current to a voltage referenced to VSS at the output.

Abstract: A voltage generator is used for generating a voltage reference with high power supply rejection. One embodiment of the circuit includes a voltage regulator and a bandgap voltage circuit and an amplifier. The voltage regulator including an input node is coupled to an external power supply for generating a regulated voltage source. A bandgap voltage circuit includes a first and a second resistor and a first and a second transistor to generate a voltage difference between the base-to-emitter voltages of the first and the second transistors. The second resistor is coupled to the first resistor and the first transistor for generating the first predetermined voltage in response to the voltage difference. An amplifier circuit is coupled to the first transistor of the bandgap voltage circuit for receiving a first amplifying signal and generating an amplified signal so as to regulate the regulated voltage source.

Abstract: A reference current generator circuit that suppresses variations in the production of parts and attains a voltage reduction, thereby suppressing power consumption. The reference current generator circuit includes current generating circuit parts, differential amplifying circuit parts, output circuit parts that output first and second reference currents respectively, and a resistor for converting a reference current to a reference voltage. Since respective voltages are kept at the same potential, respective PMOSs are operated in a linear region by means of the differential amplifying circuit pads.

Abstract: A reference current circuit includes a differential amplifier amplifying a difference in potential between a reference voltage and a first node and outputting the amplified potential difference to a second node, and adjusting transistors connected between a supply voltage and the first node. The reference current circuit further includes switches provided correspondingly to the adjusting transistors to apply a voltage of the second node to control electrodes of the adjusting transistors in response to control signals that are respectively input to the switches. The reference current circuit further includes a resistance connected between the first node and a common potential, and an output transistor having its conduction state responsive to the voltage of the second node for controlling a current supplied from the supply voltage to a load.

Abstract: An LDO regulator (10) produces an output voltage (Vout) by applying the output voltage to a feedback input (6) of a differential input stage (10A) and applying an output (3) of the differential input stage to a gate of a first follower transistor (MP4) having a source coupled to an input (8) of a class AB output stage (10C) which generates the output voltage. Demanded load current is supplied by the output voltage during a dip in its value to a gate of a second follower transistor (MP5) having a gate coupled to the output of the input stage to decrease current in a current mirror (MN5,6) having an output coupled to a current source (I1) and a gate of an amplifying transistor (MN7). This causes the current source to rapidly turn on the amplifying transistor to cause it to rapidly turn on a cascode transistor (MN3), causing it to turn on a pass transistor (MP3) of the output stage.

Abstract: A reliable start-up circuit for starting a bandgap type voltage reference generator which ensures that the bandgap reference cell will operate at a stable operating point before the start-up circuit is disabled.

Abstract: An object of the invention is to provide a reference voltage generation circuit relatively unaffected by ambient temperature, capable of supplying reference voltage equal to or less than the bandgap voltage of silicon. The reference voltage generation circuit includes: a current generation circuit which generates current; and a current-voltage conversion circuit which converts the current generated by said current generation circuit into voltage to generate reference voltage. The current generation circuit generates current which varies in value according to ambient temperature of the current generation circuit. The current-voltage conversion circuit includes two resistors, in which the current generated by the said current generation circuit flows, and which perform voltage conversion. One of the resistors has a positive temperature coefficient and the other has a negative temperature coefficient.

Abstract: A bandgap reference circuit having a low sensitivity to temperature and supplied voltage installs a compensation circuit on a bandgap reference circuit to substitute a prior art that uses a resistor to match the circuit startup purpose and solve the problem of startup error caused by the manufacturing error. The bandgap reference circuit includes a first amplifier, a second amplifier, and a reference circuit having a plurality of transistors and a plurality of bipolar junction transistors, and the bandgap reference circuit is electrically connected to a same supplied power of which the reference circuit is electrically connected and also includes a plurality of transistors and a compensation circuit of the second amplifier, so as to output a stable startup voltage which has a low sensitivity to the change of temperature and the change of supplied voltage.

Abstract: One embodiment of the present invention includes a system for providing a soft-start for a power regulator comprising a differential transistor pair that receives an input current and conducts a first current through a first transistor and a second current through a second transistor. One of the first and second current changes in response to a change in the other to maintain a sum of the first and second current being substantially equal to the input current. The system also comprises a comparator that provides an output signal based on a comparison of a first input voltage and a second input voltage associated with the first current and the second current, respectively. The system further comprises a current source activated by the output signal to charge a capacitor that increases a soft-start reference voltage associated with control of the power regulator and which controls the change in the other of the first and second current.

Abstract: In a driver circuit constructing a switching power supply device that switches power transistors passing a current through a coil by a PWM mode, a current detection transistor, which is smaller in size than the low-potential side power transistor, and a current detection resistor are provided in parallel to the low-potential side power transistor. The same control voltage as the power transistor is applied to the control terminal of the current detection transistor. An operational amplifier is formed, that has the potential of the connection node between the current detection transistor and the current detection resistor applied to its inverse input terminal and a feedback loop, so as to make a pair of input terminals of the operational amplifier be at the same potential. A signal produced by the current detection resistor is thus outputted as a current detection signal.

Abstract: To provide a current sensing circuit that detects a difference between a cell current and a reference current. The current sensing circuit includes: current mirror circuits of which the input terminal is connected with a reference current source; a differential amplifier of which the one input terminal is supplied with a potential of an electrical connection point between an output terminal of the current mirror circuit and a memory cell and of which the other input terminal is supplied with a reference potential; and an equalizing circuit that short-circuits the both input terminals of the differential amplifier in response to an equalizing signal. Thereby, the both input terminals can be kept at the same potential immediately before a sensing operation starts, and thus, even when the cell current is weak, a highly sensitive sensing operation can be performed at high speed.

Abstract: An inverse temperature characteristic generating circuit decreases an output voltage Vout by a voltage VGS, and supplies the resultant voltage as a voltage VA to a temperature characteristic generating circuit. The temperature characteristic generating circuit includes a differential amplification circuit that receives a terminal voltage VAP between resistances R22 and R23 and an emitter voltage VAM of a bipolar transistor T21, and outputs a control signal VC. When the terminal voltages VAP and VAM are equal to each other, an operation of a circuit is stable. The temperature characteristic of the voltage VA during the stable operation, and the temperature characteristic of the voltage VGS are inverse to each other and therefore cancel each other, so that the constant voltage Vout independent of temperature is output. In addition, the output terminal is not connected via a resistance to a ground, so that low current consumption can be easily achieved.

Abstract: A semiconductor device comprising an internal current generating section (1) for supplying an output current (i2) dependent on an input current (i1) into an IC, an external terminal (2) for connecting an external resistor (Rex) to the input end side of the internal current generating section (1), a current limiting element (3) connoted between the input end of the internal current generating section (1) and the external terminal (2), a first current limiting section (4) for pulling in the input current (i1) when one end voltage VA of the current limiting element (3) is higher than a first threshold voltage VB, and a second current limiting section (5) for pulling in the input current (i1) when the terminal voltage VC of the external terminal (2) is higher than a second threshold voltage. System down can be avoided by operating the internal circuit surely regardless of the state of the external terminal.

Abstract: A voltage regulator and a voltage regulating method thereof and a voltage generator using the voltage regulator are disclosed by the present invention. The voltage regulator of the present invention uses a first switching unit and a second switching unit to respectively provide an operational transconductance amplifier (OTA) with different closed-loop feedback paths during a first period and a second period. In this way, an auto-zeroing unit is able to exactly store an input offset voltage presented between the inverting input terminal and the non-inverting input terminal of the OTA.

Abstract: The present invention uses two transistors instead of a sensing resistor to provide a constant current source for a load such as an array of light emitting diodes (“LEDs”). In the present invention, a bias current is applied to a branch of the circuit. The drain-to-source voltages of two transistors are matched. The voltage at the gate of both transistors is controlled based on the bias current and the drain-to-source current of the first of the two transistors. The second of the two transistors is sized such that source current of the second transistor is a multiple of the source current of the first transistor for a given gate voltage. By the techniques of this invention, the load current in a circuit is efficiently kept constant at a multiple of the input bias current.

Abstract: A voltage reference circuit is provided. The voltage reference circuit includes a first PTAT voltage generator and an amplifier. The first PTAT voltage generator is operable to generate a first PTAT voltage. The amplifier, which is coupled to the first PTAT voltage generator, comprises a second PTAT voltage generator that is complementary to the first PTAT voltage generator. The second PTAT voltage generator is operable to generate a second PTAT voltage. The amplifier is operable to generate a reference voltage based on the first PTAT voltage and the second PTAT voltage.

Abstract: A reference current generator configured to produce matched and isolated current references is disclosed. The reference current generator includes a primary reference generator operative to produce a first reference current. The reference current generator further includes a duplicate reference generator operative to produce a second reference current. An adjustment circuit coupled to the primary reference generator and the duplicate reference generator is configured such that the first reference current is substantially matched to and isolated from the second reference current.

Abstract: A reference voltage generator circuit comprises a first current path and a second current path. The first current path is formed between an input terminal supplied with a first reference voltage and an output terminal and including a first diode and a first resistor serially connected from the input terminal. The second current path is formed between the input terminal and the output terminal and including a second diode, a second resistor and a third resistor serially connected from the input terminal. A comparator is supplied with a voltage on a node between the first diode and the first resistor and a voltage on a node between the second resistor and the third resistor for comparative amplification. A transistor is connected between the output terminal and a second reference voltage and having a control terminal to receive an output from the first comparator.

Abstract: A band gap voltage reference circuit comprises a first band gap (BG) circuit that generates a first BG voltage potential. A second BG circuit includes a variable resistance and outputs a second BG voltage potential that is related to a value of said variable resistance. A calibration circuit communicates with said first and second BG circuits, adjusts said variable resistance based on said first BG voltage potential and said second BG voltage potential, and selectively shuts down said first BG circuit.

Abstract: In one embodiment, a voltage reference circuit is configured to use two differentially coupled transistors to form a delta Vbe for the voltage reference circuit.

Abstract: An integrated circuit in accordance with one embodiment of the invention includes an oscillator circuit and a source circuit. The source circuit outputs a reference voltage and a bias current, wherein the reference voltage changes by substantially the same proportion as the bias current. The oscillator circuit is coupled to receive the reference voltage and the bias current from the source circuit. The oscillator circuit outputs an oscillating electrical signal.

Abstract: A constant voltage generating circuit according to the present invention includes a reference voltage generation source 1, a differential amplifier 2 that receives an output voltage (REF1) of the reference voltage generation source 1 at one terminal and receives a potential (VREF2), generated by adding a predetermined potential difference to a regulator voltage (VREG), at another terminal, and switching means 6 that controls the current amount of an output terminal 10 of the reference voltage generation source 1 so that the current amount increases for a fixed period of time immediately after the power is turned on. The switching means 6, which is turned on/off based on VREF2, stabilizes the output voltage (REF1) of the reference voltage generation source 1 quickly after the power is turned on and then stabilizes the regulator voltage (VREG).

Abstract: An IC current reference includes a reference voltage Vref, a current mirror, and a transistor connected between the mirror input and a first I/O pin and which is driven by Vref. A resistor external to the IC and having a resistance R1 is coupled to the first I/O pin such that it conducts a current Iref which is proportional to Vref/R1; use of a low TC/VC resistor enables Iref to be an accurate and stable reference current. The current mirror provides currents which are proportional to Iref, at least one of which is provided at a second I/O pin for use external to the IC. One primary application of the reference current is as part of a regulation circuit for a negative supply voltage channel, which can be implemented with the same number of external components and I/O pins as previous designs, while providing superior performance.

Abstract: Provided is a voltage control circuit which suppresses a calorific value that generates when short-circuit fault occurs even if a voltage value of an input voltage is large. At the time of short-circuit fault, an additional control voltage Va whose voltage value becomes larger when the voltage value of the input voltage Vin is larger is input to the voltage control p-channel MOS transistor (110) from a transistor control MOS transistor (160), to thereby increase resistance of the voltage control p-channel MOS transistor (110) to suppress a short-circuit current. As a result, when the input voltage Vin is larger, the current value of a holding current or a calorific value after the short-circuit protecting operation has been conducted can be suppressed.

Abstract: A stable high-precision current detection circuit capable of continuously detecting load current through a load with extremely reduced power loss. The current detection circuit has a power transistor and a current detection transistor that are fed with a common power supply voltage and a common switching signal. A buffer circuit is provided for supplying an idling current to the output node of the current detection transistor while realizing the same virtual potential at the output terminals of these transistors. Thus, the buffer circuit always functions as a class-A amplifier.

Abstract: In a driver circuit constructing a switching power supply device that switches power transistors passing a current through a coil by a PWM mode, a current detection transistor, which is smaller in size than the low-potential side power transistor, and a current detection resistor are provided in parallel to the low-potential side power transistor. The same control voltage as the power transistor is applied to the control terminal of the current detection transistor. An operational amplifier is formed, that has the potential of the connection node between the current detection transistor and the current detection resistor applied to its inverse input terminal and a feedback loop, so as to make a pair of input terminals of the operational amplifier be at the same potential. A signal produced by the current detection resistor is thus outputted as a current detection signal.

Abstract: A control circuit for a DC voltage supply is provided that includes a circuit, an error amplifier and modulator. The circuit is operable to measure a voltage difference between a negative voltage rail and a ground reference in the DC voltage supply. The circuit is further operative to create an offset voltage proportional with the measured voltage difference. The circuit is further yet operative to add the offset voltage to a reference voltage to create a modified reference voltage. The error amplifier has a first input coupled to receive the modified reference voltage and a second input coupled to a positive voltage rail in the DC voltage supply. The error amplifier further has an output. The modulator is coupled to the output of the error amplifier. The modulator is operative to maintain the positive rail at a select value corresponding to the modified reference voltage.

Abstract: A reference voltage generating circuit is described. The circuit includes a current generating section that generates a first current having a positive temperature coefficient, a voltage generating section that generates a voltage having a negative temperature coefficient, a synthesis section that generates a voltage which is the sum of a voltage having a positive temperature coefficient and developed across both terminals of a resistor, where the voltage has a negative temperature coefficient, and a compensation current generating section that generates a second current having a positive temperature coefficient. The current corresponding to the sum of said first and second currents is caused to flow through the resistor. The synthesis section generates a voltage which is a sum of a terminal voltage of the resistor by the sum current of the first and second currents and the voltage having a negative temperature coefficient.

Abstract: A constant-voltage circuit in which a response speed for a sudden change of an input voltage or a sudden change of a load current can be fast are disclosed. In normal operating conditions, a first control circuit (error amplifier circuit) having an excellent direct-current characteristic controls operations of an output voltage control transistor and an output voltage is made a constant voltage. When the output voltage is suddenly decreased, before the first control circuit controls the operations of the output voltage control transistor by responding to the sudden decrease of the output voltage, an amplifier circuit having a high-speed response characteristic amplifies the change of the output voltage, and when the amplified voltage obtained by the amplification is suddenly decreased, a second control circuit controls the operations of the output voltage control transistor for a predetermined period. With this, the output voltage can be a constant voltage.

Abstract: A reference circuit. Included are first and second reference circuit blocks, first and second controllable current sources connected to supply current through the first and second reference circuit blocks respectively, an amplifier having non-inverting and inverting inputs responsive to the voltages developed by the first and second reference circuit blocks respectively and having an output connected to control the currents provided by the first and second current sources, and an output stage having a reference output controlled by the output of the amplifier. The reference circuit further comprises start-up circuitry, including a latch having an output indicating its state and being responsive to a signal indicative of the output from the reference output to latch from a first state into a second state when that signal passes a first threshold, and a switch that is responsive to the output of the latch to supply a control signal.

Abstract: A voltage reference generator includes multiple closed loop voltage references. Each of the closed loop voltage references uses a flash cell with a variable threshold voltage and a feedback loop to trim a reference voltage. The voltage reference generator includes sample and hold capacitors in output stages to allow reference voltages to be refreshed during a standby mode of operation.

Abstract: An apparatus for generating a reference voltage in a semiconductor memory apparatus according includes: a first voltage generating unit configured to generate a voltage proportional to temperature; a second voltage generating unit configured to generate a voltage inversely proportional to temperature; and a reference voltage generating unit including a first adjusting unit connected with the first voltage generating unit and a second adjusting unit connected with the second voltage generating unit, configured to select the first adjusting unit or the second adjusting unit according to a difference between a reference voltage obtained by the first voltage generating unit and the second voltage generating unit and a target voltage, and adjust the reference voltage thereby outputting a constant reference voltage regardless of a variation in temperature.

Abstract: A startup circuit for activating a bandgap circuit is provided, including a switching circuit, an activating circuit, and a controlling circuit. The controlling circuit is used for monitoring and comparing two voltages to determine whether the switching circuit should be turned on so as to activate the bandgap circuit. One of the two voltages that are monitored is a zero temperature coefficient voltage, and the other of the two voltages that are monitored is a negative temperature coefficient voltage.

Abstract: A method is provided that includes receiving a classification voltage at a powered device from a powered network and providing a classification signature to the powered network in response to receiving the classification voltage to specify a power requirement of the powered device. The method further includes deriving a reference current within the powered device and adjusting a current limit as a function of the reference current.

Abstract: An integrated circuit comprises a gain stage circuit coupled to a compensation circuit. Both the gain stage circuit and the compensation circuit respectively comprise a first current source and a second current source that are subject to the same process variations. A negative feedback circuit is used to generate a corrective current in relation to the second current source, indicative of a current that needs to flow through a load in addition to a current flowing through the second current source in order for a variable voltage to be substantially equal to a reference voltage used to drive the first and second current sources. A compensating current corresponding to the corrective current generated for the second current source is applied to the first current source to compensate for process variation in the gain stage circuit in respect to the first current source.

Abstract: A current source apparatus for reducing interference with noise is provided. The current source apparatus includes a controllable current source and a feedback controller. The controllable current source provides an output current according to a control signal and produces a feedback signal according to the output of the controllable current source. The feedback controller is coupled to the controllable current source for receiving the feedback signal, and the feedback controller adjusts the control signal based on the feedback signal and outputs the control signal for controlling the controllable current source to output a stable output current.

Abstract: The present invention discloses a current generating apparatus for generating an output current. The current generating apparatus includes: a first current mirror; a first bias current generator for providing a first bias current, and the first bias current generator includes: a first current source for providing the first current; and a capacitive device for conducting a reference current; a second current mirror for generating a second mirror current; a second bias current generator for generating a second current; a third current source for providing a third current, wherein the second mirror current is equal to the third current; a feedback circuit; and a fourth current source for providing a fourth current, wherein the output current is outputted at an output node of the first current mirror.

Abstract: Provided is a current supply for providing a charge current to a load. The current supply includes: a driving transistor, providing the charge current to the load; a sensing transistor, limiting the charge current; a pulling low transistor, pulling low a controlling node which controls the driving transistor and the sensing transistor; a constant voltage controller, pulling up the controlling node, controlling the conduction state of the driving transistor and accordingly maintaining the voltage across the load at the first reference voltage, when a voltage across the load rises up and comes close to a first reference voltage; and a constant current controller, controlling the controlling node and the pulling low transistor to limit the charge current to be constantly provided to the load, when the voltage across the load drops much lower than the first reference voltage.