A current source circuit

Abstract

The present invention provides a current source circuit, including a startup circuit, a current mirror circuit, and a constant temperature current generating circuit. The input end of the startup circuit is connected to a shutdown control signal PD of a current source, and the output end thereof is respectively connected to the current mirror circuit and the constant temperature current generating circuit. The current mirror circuit is connected to the constant temperature current generating circuit and divides the voltage, and the current mirror circuit outputs a bias current. The startup circuit includes a MOS tube M5 and a capacitor C, the gate of the MOS tube M5 is connected to the shutdown control signal PD of the current source, and the common end of the MOS tube M5 and the capacitor C is respectively connected to the current mirror circuit and the constant temperature current generating circuit. The current source circuit of the present invention has a relatively simple structure, does not require a BJT device, occupies a small area, and after the circuit is started, the capacitor does not pass direct current and has no power consumption, thereby realizing a current source circuit with zero power consumption at startup current, small area occupation, and constant current temperature.

Description

Technical Field

[0001] The present invention relates to the technical field of integrated circuits, and in particular to a current source circuit. Background Art

[0002] Current source is an essential circuit unit in integrated circuits. Its performance and area are crucial. Traditional small-area current source circuits such as Figure 1 As shown in the figure, the core circuit is mainly composed of NMOS tubes M1 and M2, PMOS tubes M3, M4, M5 and resistor R. For the convenience of description, the startup circuit is omitted in the circuit. The width-to-length ratio of M2 is K times that of M1, and the width-to-length ratios of M3 and M4 are equal. The width-to-length ratio of M5 is P times that of M3 and M4. Figure 1 The expression of the bias current Iref generated in is as follows:

[0003]

[0004] where μ N 、c ox They are respectively the carrier mobility of the NMOS field effect tube and the capacitance per unit area of ​​the gate oxide. N It is a process parameter with a trend opposite to that of temperature change, so the above equation is a positive temperature curve. Practical verification has proved that due to the process deviation of CMOS devices and resistors, when the temperature and voltage change, the bias current Iref has a deviation of ±100% or even more, so that the actual circuit power consumption varies greatly, which is not conducive to power consumption management and circuit design.

[0005] For power consumption management, it is necessary to design a current source whose current varies little with temperature. In traditional designs, BJT devices are often used, and BJT requires a large circuit area. Therefore, it is necessary to propose a current source circuit that meets the characteristics of small area and small current variation with temperature. Summary of the invention

[0006] In view of the defects existing in the prior art, the object of the present invention is to provide a current source circuit that meets the characteristics of small area and small current change with temperature.

[0007] In order to achieve the above object, the specific technical solution adopted by the present invention is as follows:

[0008] A current source circuit comprises a start-up circuit, a current mirror circuit, and a constant temperature current generating circuit, wherein an input end of the start-up circuit is connected to a shutdown control signal PD of a current source, and an output end thereof is respectively connected to the current mirror circuit and the constant temperature current generating circuit, the current mirror circuit is connected to the constant temperature current generating circuit and divides the voltage, and the current mirror circuit outputs a bias current; the start-up circuit comprises a MOS tube M5 and a capacitor C, a gate of the MOS tube M5 is connected to a shutdown control signal PD of a current source, and a common end of the MOS tube M5 and the capacitor C is respectively connected to the current mirror circuit and the constant temperature current generating circuit.

[0009] Preferably, the MOS tube M5 is an NMOS tube.

[0010] Preferably, the constant temperature current generating circuit includes a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a resistor R1 and a resistor R2, the gate of the MOS tube M1 is connected to the gate of the MOS tube M2, the gate of the MOS tube M3 is connected to the gate of the MOS tube M4, the MOS tube M3 is connected to the MOS tube M1, the MOS tube M4 is connected to the MOS tube M2, one end of the resistor R1 is connected to the MOS tube M2, and the other end is grounded, one end of the resistor R2 is connected to the common end of the MOS tube M4 and the MOS tube M2, and the other end is grounded.

[0011] Preferably, the MOS tube M1, MOS tube M2, MOS tube M3, and MOS tube M4 are NMOS tubes.

[0012] Preferably, the width-to-length ratio of the MOS tube M2 is a set multiple of that of the MOS tube M1 , and the width-to-length ratios of the MOS tube M3 and the MOS tube M4 are equal.

[0013] Preferably, the current mirror circuit includes MOS tube M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, and MOS tube M11. MOS tube M8 and MOS tube M6 are connected in sequence, the MOS tube M9 and MOS tube M7 are connected in sequence, the MOS tube M10 and MOS tube M11 are connected in sequence, the gates of the MOS tube M8, MOS tube M9 and MOS tube M10 are connected, the gates of the MOS tube M6, MOS tube M7 and MOS tube M11 are connected, and the MOS tube M6 and MOS tube M7 are respectively connected to the constant temperature current generating circuit.

[0014] Preferably, the MOS tube M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, and MOS tube M11 are PMOS tubes.

[0015] Preferably, the width-to-length ratios of the MOS tube M6 and the MOS tube M7 are equal, the width-to-length ratios of the MOS tube M8 and the MOS tube M9 are equal, the width-to-length ratio of the MOS tube M11 is P times that of the MOS tube M6 and the MOS tube M7, and the width-to-length ratio of the MOS tube M10 is P times that of the MOS tube M8 and the MOS tube M9, where P is a set positive integer.

[0016] The beneficial effects of the present invention are: the current source circuit is relatively simple in structure, does not require BJT devices, occupies a small area, and after the circuit is started, the capacitor does not pass direct current and has no power consumption, thereby realizing a current source circuit with zero power consumption at the starting current, small area occupation and constant current temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0018] Figure 1 It is a circuit schematic diagram of a small area current source circuit in the prior art;

[0019] Figure 2 It is a circuit principle diagram of a current source circuit of the present invention.

[0020] In the figure, 1-starting circuit, 2-current mirror circuit, 3-constant temperature current generating circuit DETAILED DESCRIPTION

[0021] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, other embodiments obtained by ordinary technicians in this field without creative work are all within the scope of protection of the present invention.

[0022] In the description of the present invention, it should be noted that the terms "vertical", "up", "down", "horizontal", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0023] In the description of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0024] like Figure 2 As shown, the present invention proposes a current source circuit, including a startup circuit 1, a current mirror circuit 2, and a constant temperature current generating circuit 3. The input end of the startup circuit 1 is connected to the shutdown control signal PD of the current source, and its output end is respectively connected to the current mirror circuit 2 and the constant temperature current generating circuit 3. The current mirror circuit 2 is connected to the constant temperature current generating circuit 3 and divides the voltage, and the current mirror circuit outputs a bias current; the startup circuit includes a MOS tube M5 and a capacitor C, the gate of the MOS tube M5 is connected to the shutdown control signal PD of the current source, and the common end of the MOS tube M5 and the capacitor C is respectively connected to the current mirror circuit and the constant temperature current generating circuit. The MOS tube M5 is an NMOS tube.

[0025] Preferably, the constant temperature current generating circuit comprises a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a resistor R1 and a resistor R2, the gate of the MOS tube M1 is connected to the gate of the MOS tube M2, the gate of the MOS tube M3 is connected to the gate of the MOS tube M4, the MOS tube M3 is connected to the MOS tube M1, the MOS tube M4 is connected to the MOS tube M2, one end of the resistor R1 is connected to the MOS tube M2, and the other end is grounded, one end of the resistor R2 is connected to the common end of the MOS tube M4 and the MOS tube M2, and the other end is grounded. The MOS tube M1, the MOS tube M2, the MOS tube M3, and the MOS tube M4 are NMOS tubes. The width-to-length ratio of the MOS tube M2 is set (K, K is a set positive integer) times that of the MOS tube M1, and the width-to-length ratio of the MOS tube M3 is equal to that of the MOS tube M4.

[0026] Preferably, the current mirror circuit includes MOS tube M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, and MOS tube M11, MOS tube M8 and MOS tube M6 are connected in sequence, MOS tube M9 and MOS tube M7 are connected in sequence, MOS tube M10 and MOS tube M11 are connected in sequence, the gates of MOS tube M8, MOS tube M9 and MOS tube M10 are connected, the gates of MOS tube M6, MOS tube M7 and MOS tube M11 are connected, and MOS tube M6 and MOS tube M7 are respectively connected to the constant temperature current generating circuit. The MOS tube M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, and MOS tube M11 are PMOS tubes. The width-to-length ratio of the MOS tube M6 is equal to that of the MOS tube M7, the width-to-length ratio of the MOS tube M8 is equal to that of the MOS tube M9, the width-to-length ratio of the MOS tube M11 is P times that of the MOS tube M6 and the MOS tube M7, and the width-to-length ratio of the MOS tube M10 is P times that of the MOS tube M8 and the MOS tube M9, where P is a set positive integer. Bias current I REF =P×I0.

[0027] The working principle of the present invention is as follows:

[0028] Since the width-to-length ratio of M6 and M7 is equal, and the width-to-length ratio of M8 and M9 is equal, the M6 ​​and M8 branches mirror the current of the M7 and M9 branches 1:1, so I1 = I2. For the constant temperature current generating circuit,

[0029] V A +V GS3 =V GS4 +V B

[0030] Since the width-to-length ratio of M3 and M4 is equal, and I1=I2, the voltage V A =V B , and because

[0031] V GS1 =V GS2 +I3*R1

[0032] Then the current I1

[0033]

[0034] In the above formula, due to μ Nis a process parameter with a trend opposite to that of temperature change, so the first term of the equation generates a current with a positive temperature curve. Since the gate and drain of NOMS are connected together, the M1 tube is a diode connection, and the diode voltage decreases with increasing temperature, so the second term of the equation is a negative temperature curve. By adjusting the appropriate parameters and the positive and negative temperature coefficient currents, a bias current close to zero temperature coefficient can be designed, thereby

[0035]

[0036] For the startup circuit, when PD is at a high level AVD, the NMOS tube M5 is turned on to ground, and the voltage V E =0, thus pulling the gates of M8 and M9 to the ground, making them in the on state, while the gates of M6 and M7 are the PD high level voltage AVD, in the off state, M6 and M7 are in high impedance state, thus shutting down the entire circuit. When the circuit is working normally, PD switches from AVD to 0 level, making M6 and M7 work in a conducting switch state, and is also equivalent to a weaker cascode tube, improving the accuracy of the mirror circuit. At this time, M8, M6, M3, and M1 establish a current path, so that V C , V A With the initial voltage, M4 and M2 are turned on, and the startup begins. Since the gate of M5 is switched to 0 level, M5 becomes high impedance, and the power supply AVD charges point E through capacitor C, so that the voltage V E Gradually increase, the gates of M8 and M9 gradually increase, and when the circuit is balanced, it no longer changes, and the circuit startup is completed. After the startup is completed, since M5 is high resistance and the capacitor is not DC, the startup circuit does not consume any power.

[0037] The beneficial effects of the present invention are: the current source circuit is relatively simple in structure, does not require BJT devices, occupies a small area, and after the circuit is started, the capacitor does not pass direct current and has no power consumption, thereby realizing a current source circuit with zero power consumption at the starting current, small area occupation and constant current temperature.

[0038] With the above-mentioned ideal embodiments of the present invention as inspiration, through the above-mentioned description, those skilled in the art can make various changes and modifications without departing from the technical concept of the present invention. The technical scope of the present invention is not limited to the contents of the specification, and its technical scope must be determined according to the scope of the claims.

Claims

1. A current source circuit, characterized in that: It includes a startup circuit, a current mirror circuit, and a constant temperature current generating circuit. The input end of the startup circuit is connected to a shutdown control signal PD of a current source, and the output end thereof is respectively connected to the current mirror circuit and the constant temperature current generating circuit. The current mirror circuit is connected to the constant temperature current generating circuit and divides the voltage, and the current mirror circuit outputs a bias current. The startup circuit includes a MOS tube M5 and a capacitor C. The gate of the MOS tube M5 is connected to the shutdown control signal PD of the current source, and the common end of the MOS tube M5 and the capacitor C is respectively connected to the current mirror circuit and the constant temperature current generating circuit. The constant temperature current generating circuit comprises a MOS tube M1, a MOS tube M2, a MOS tube M3, a MOS tube M4, a resistor R1 and a resistor R2. The gate of the MOS tube M1 is connected to the gate of the MOS tube M2, the gate of the MOS tube M3 is connected to the gate of the MOS tube M4, the MOS tube M3 is connected to the MOS tube M1, the MOS tube M4 is connected to the MOS tube M2, one end of the resistor R1 is connected to the MOS tube M2, and the other end is grounded, one end of the resistor R2 is connected to the common end of the MOS tube M4 and the MOS tube M2, and the other end is grounded, and the MOS tube M1, the MOS tube M2, the MOS tube M3, and the MOS tube M4 are NMOS tubes; The current mirror circuit includes MOS tube M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, and MOS tube M11. MOS tube M8 and MOS tube M6 are connected in sequence, the MOS tube M9 and MOS tube M7 are connected in sequence, the MOS tube M10 and MOS tube M11 are connected in sequence, the gates of the MOS tubes M8, MOS tube M9 and MOS tube M10 are connected, the gates of the MOS tubes M6, MOS tube M7 and MOS tube M11 are connected, the MOS tubes M6 and MOS tube M7 are connected to the constant temperature current generating circuit respectively, and the MOS tubes M6, MOS tube M7, MOS tube M8, MOS tube M9, MOS tube M10, and MOS tube M11 are PMOS tubes.

2. A current source circuit according to claim 1, characterized in that: The MOS tube M5 is an NMOS tube.

3. A current source circuit according to claim 1, characterized in that: The width-to-length ratio of the MOS tube M2 is a set multiple of that of the MOS tube M1 , and the width-to-length ratios of the MOS tube M3 and the MOS tube M4 are equal.

4. A current source circuit according to claim 1, characterized in that: The width-to-length ratio of the MOS tube M6 is equal to that of the MOS tube M7, the width-to-length ratio of the MOS tube M8 is equal to that of the MOS tube M9, the width-to-length ratio of the MOS tube M11 is P times that of the MOS tube M6 and the MOS tube M7, and the width-to-length ratio of the MOS tube M10 is P times that of the MOS tube M8 and the MOS tube M9, where P is a set positive integer.

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