A trimming circuit for a bandgap reference source to reduce oscillation

Abstract

A trimming circuit for a bandgap reference source to reduce oscillation, characterized in that: the circuit is connected between the device voltage terminal of the bandgap reference source and the pre-stabilized voltage output terminal; and the circuit includes a reference resistor and multiple trimming branches arranged in a preset order; wherein, the preset order is set based on the oscillation direction when the pre-stabilized voltage oscillates. The method of the present invention realizes the reasonable design of the trimming module in the bandgap circuit according to the mutation direction of the output voltage of the pre-stabilization module under the working condition of the circuit, thereby minimizing the circuit oscillation and enabling the circuit to be quickly stabilized.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and more particularly, to a trimming circuit for a bandgap reference source that reduces oscillation. Background Art

[0002] Currently, a DC-DC (Direct Current-Direct Current) converter is a voltage converter that converts an input voltage and effectively outputs a fixed voltage. Such converters are widely used in products such as mobile phones, MP3 players, digital cameras, and portable media players.

[0003] In a DC-DC converter with a wide input range, a pre-stabilization module is often used to supply power to the bandgap circuit. After the bandgap circuit generates a sufficiently stable bandgap voltage, it provides voltage and current biasing for other modules such as an LDO (Low Dropout Regulator). Since the LDO needs to supply power to other low-voltage modules, the output terminal of the LDO sometimes needs to be shorted to the output terminal of the pre-stabilization module. Generally speaking, the LDO needs to have a strong load-carrying capacity, that is, the short-circuit current of the LDO needs to reach a relatively high index, such as more than 100 mA. However, when the short-circuit current of the LDO is large, it is difficult for the bandgap circuit to maintain transient stability.

[0004] On the other hand, there is a technical solution in the prior art to provide a trimming module for the bandgap circuit, that is, different process corners are used to trim the bandgap voltage to a more accurate voltage value, thereby improving the output accuracy of the circuit.

[0005] Furthermore, when both the LDO and the bandgap circuit are connected to the pre-stabilization module, as the LDO suddenly accesses a heavy load, the output voltage of the pre-stabilization module will drop suddenly, resulting in a parasitic capacitance current in the switching transistor in the conduction state in the trimming module of the bandgap circuit. During the sudden change of the pre-stabilization voltage, the output of the bandgap voltage realizes a reverse mutation with the pre-stabilization voltage. For the LDO, its output terminal drops suddenly and its input terminal rises suddenly, causing the output of the bandgap circuit and the pre-stabilization module, which are the feedback loops of the LDO, to continuously adjust. And due to the existence of phase delay, periodic oscillation of the bandgap circuit and the pre-stabilization module occurs, and it is difficult for the DC-DC converter to reach a stable state in a short time.

[0006] To solve the above problems, there is an urgent need for a trimming circuit for a bandgap reference source that reduces oscillation. Summary of the Invention

[0007] To solve the deficiencies in the prior art, the purpose of the present invention is to provide a trimming circuit for a bandgap reference source that reduces oscillation. According to the operating conditions of the circuit, the reasonable design of the trimming module in the bandgap circuit is realized based on the mutation direction of the output voltage of the pre-stabilization module, thereby minimizing circuit oscillation.

[0008] The present invention adopts the following technical solutions.

[0009] A trimming circuit for a bandgap reference source that reduces oscillation, the circuit is connected between the device voltage terminal of the bandgap reference source and the pre-stabilized voltage output terminal; and the circuit includes a reference resistor and multiple trimming branches arranged in a preset order; wherein, the preset order is set based on the oscillation direction when the pre-stabilized voltage oscillates.

[0010] When the LDO is connected to a heavy load, or its load mutates, or the pre-stabilized voltage mutates due to various reasons, it will cause serious oscillation of the circuit. To solve this problem, the present invention improves the order between the resistors and branches of the trimming circuit.

[0011] Preferably, when the pre-stabilized voltage oscillates in a sudden drop manner, maximize the ratio of the transient currents of each pole of the switching transistor in the trimming branch Wherein, is the transient current of the parasitic capacitance between the gate and source of the switching transistor in the conducting state when the pre-stabilized voltage suddenly drops; is the transient current of the parasitic capacitance between the gate and drain of the switching transistor in the conducting state when the pre-stabilized voltage suddenly drops.

[0012] Preferably, arrange the switching transistor corresponding to the trimming branch with the highest trimming probability in the trimming circuit at the edge of the module of the trimming circuit to achieve the ratio of the transient currents of the switching transistor increase.

[0013] Preferably, arrange the branch with the highest trimming accuracy among the multiple trimming branches at the edge of the module of the trimming circuit; and adjust the size of the switching transistor in the adjusting branch.

[0014] Preferably, when the pre-stabilized voltage oscillates in a sudden drop manner, maximize the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch

[0015] The bandgap voltage output by the circuit is V bg0 , and this voltage value should be equal to the sum of the voltage divisions of each resistor in the trimming circuit, the voltage divisions of each resistor in the bandgap reference source, and the voltage between the base and emitter of the transistor. Therefore, the equation V bg0 =I s0 R down +I d0 R up +V be2. In the above formula, I s0 is the source current of the switch transistor NM0 that is the only one in the on state at this time, and I d0 is the drain current of this transistor. In addition, R down is the resistance value of the equivalent resistance formed by all the resistors between the switch transistor and the transistor Q2 below. And R up is the sum of all the resistors between the switch transistor and the pre-stabilized voltage output terminal above.

[0016] Preferably, the trimming up-resistance is the resistance value of the equivalent resistance between the switch transistor closest to the pre-stabilized voltage output terminal in the on state and the pre-stabilized voltage output terminal after the states of the switch transistors in multiple trimming branches are determined.

[0017] Preferably, the trimming down-resistance is the resistance value of the equivalent resistance between the switch transistor closest to the base of the transistor in the bandgap reference source in the on state and the base of the transistor after the states of the switch transistors in multiple trimming branches are determined.

[0018] Preferably, a reference resistor is directly connected to the device of the bandgap reference source and connected to the pre-stabilized voltage output terminal after passing through multiple trimming branches.

[0019] Preferably, the output terminal of the trimming circuit is connected to the LDO.

[0020] Preferably, when the pre-stabilized voltage oscillates in a sudden increase manner, minimize the ratio of the transient currents of each pole of the switch transistor in the trimming branch and the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch

[0021] In order to make the bandgap voltage V′ bg0 relative to V bg0 change in the same direction as the decrease direction of VCC as much as possible when VCC suddenly decreases, so as to avoid oscillation, it can be achieved by maximizing the ratio of the transient currents of each pole of the switch transistor in the trimming branch or by maximizing the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch .

[0022] The beneficial effect of the present invention is that, compared with the prior art, a trimming circuit for a bandgap reference source for reducing oscillation in the present invention can reasonably design the trimming module in the bandgap circuit according to the mutation direction of the output voltage of the pre-stabilization module under the working conditions of the circuit, so as to minimize the oscillation of the circuit and make the circuit quickly stable.

[0023] The beneficial effects of the present invention also include:

[0024] 1. When there is a sudden need for the LDO in the circuit to access a heavy load or a sudden transition from a heavy load to a light load, the bandgap reference trimming circuit in the present invention can adjust the connection mode of the trimming branch and the trimming resistor according to the load demand of the LDO. Its layout in the chip can reduce oscillation without changing the circuit structure or adding components. While reducing oscillation and improving the fast response ability of the circuit, it also ensures the high output accuracy of the circuit.

[0025] 2. The method of the present invention fully considers the oscillation problems in various different trimming implementation cases. During the trimming process, the on-state frequencies of each switching transistor are calculated, and the switching transistor with the highest frequency is set at the edge of the module to facilitate modifying the transient parasitic capacitance current of the switching transistor. This method is very ingenious. It does not require a large increase in the area of the trimming module, nor does it need to modify the layout of the trimming module in the entire chip, achieving a very good oscillation reduction effect at the lowest cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a schematic structural diagram of a bandgap reference trimming circuit in the prior art of the present invention;

[0027] Figure 2 is a schematic structural diagram of a bandgap reference trimming circuit for reducing oscillation in the present invention;

[0028] Figure 3 is a schematic diagram for analyzing the principle of avoiding oscillation of a bandgap reference trimming circuit for reducing oscillation in the present invention;

[0029] Figure 4 is a schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the first embodiment of a bandgap reference trimming circuit for reducing oscillation in the present invention;

[0030] Figure 5 is a high-precision schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the first embodiment of a bandgap reference trimming circuit for reducing oscillation in the present invention;

[0031] Figure 6 is a schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the second embodiment of a bandgap reference trimming circuit for reducing oscillation in the present invention;

[0032] Figure 7 is a high-precision schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the second embodiment of a bandgap reference trimming circuit for reducing oscillation in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0033] The present application will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solutions of the present invention and cannot be used to limit the protection scope of the present application.

[0034] Figure 1 It is a schematic structural diagram of a trimming circuit for a bandgap reference source in the prior art of the present invention. As Figure 1 shown, in the trimming circuit for a bandgap reference source in the prior art, it is usually connected between the device voltage terminal of the bandgap reference source and the pre-stabilized voltage output terminal. Generally speaking, this circuit includes a reference resistor and multiple trimming branches.

[0035] In this circuit, as described in the background art, when the LDO is connected to a heavy load, or its load changes suddenly, or the pre-stabilized voltage changes suddenly due to various reasons, it will cause serious oscillation of the circuit. To solve this problem, the present invention improves the structure of the trimming circuit.

[0036] Figure 2 It is a schematic structural diagram of a bandgap reference source trimming circuit for reducing oscillation in the present invention. As Figure 2 shown, a bandgap reference source trimming circuit for reducing oscillation, wherein the circuit is connected between the device voltage terminal of the bandgap reference source and the pre-stabilized voltage output terminal; and the circuit includes a reference resistor and multiple trimming branches arranged in a preset order; wherein the preset order is set based on the oscillation direction when the pre-stabilized voltage oscillates.

[0037] It can be understood that in the present invention, the position of the trimming circuit is the same as that of the trimming circuit in the prior art, and it is still connected between the bandgap reference source and the pre-stabilization module to realize the trimming of the output voltage of the bandgap reference source. The pre-stabilized voltage described in the present invention can be the voltage Vcc generated by a low-dropout linear regulator (LDO, Low Drop Out). The ratio of the number of two triodes in the reference voltage source is 8:1. However, different from Figure 1 the trimming method in, the internal structure of the trimming circuit in the present invention, such as the positional relationship between the reference resistor and multiple trimming branches, is slightly different from the solution in the prior art. Specifically, in the prior art, the order of the reference resistor and multiple trimming branches is usually arranged only according to the convenience of layout, or to reduce output error, metal wire resistance and other factors. In the present invention, the order between the above-mentioned resistor and branches is determined based on the mutation direction when the pre-stabilized voltage mutates and causes oscillation.

[0038] Preferably, when the pre-stabilized voltage oscillates in a sudden drop manner, maximize the ratio of the transient currents of each pole of the switching tube in the trimming branch wherein, is the transient current of the parasitic capacitance between the gate and source of the switching tube in the conducting state when the pre-stabilized voltage suddenly drops; is the transient current of the parasitic capacitance between the gate and drain of the switching transistor in the conducting state when the pre-stabilized voltage suddenly drops.

[0039] Preferably, when the pre-stabilized voltage oscillates in a sudden drop manner, maximize the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch

[0040] Reference Figure 2 Taking the structure of the trimming circuit in [reference] as an example, when the BG_T<4:0> signal outputs the default low level state. At this time, when all control signals are low, except for NM0, other switching transistors are in the cut-off state, while the NM0 switching transistor is in the conducting state, shielding the resistor 4R in parallel with it, and NM0 is approximately in a short-circuit state. For Figure 2 Analyzing the circuit in [reference], it can be known that the bandgap voltage output by this circuit is V bg0 , and this voltage value should be equal to the sum of the voltage divisions of the resistors in the trimming circuit, the voltage divisions of the resistors in the bandgap reference source, and the voltage between the base and emitter of the transistor. Therefore, the equation is listed as

[0041] V bg0 = I s0 R down + I d0 R up + V be2 (1)

[0042] In the above formula, I s0 is the source current of the only switching transistor NM0 that is in the on state at this time, and I d0 is the drain current of this transistor. In addition, R down is the resistance value of the equivalent resistance formed by all the resistors between the switching transistor and the transistor Q2. And R up is the sum of all the resistors between the switching transistor and the pre-stabilized voltage output terminal. In addition, V be2 is the voltage difference between the base and emitter of the second transistor Q2 in this circuit.

[0043] According to the above formula, when the circuit is in a stable state, the magnitude of V bg0 is related to the values of the above resistors and currents. And when the circuit is in a dynamic situation, for example, when the LDO instantaneously switches to the heavy load state, the pre-stabilized voltage, that is, VCC in the present invention Figure 2 will instantaneously decrease, which causes a transient current to be generated in the parasitic capacitance of the switching transistor NM0 in the on state. Specifically, the parasitic capacitances are the parasitic capacitance C gd between the gate and drain of the NM0 transistor and the parasitic capacitance C gs between the gate and source.. When a transient current occurs, the transient currents generated by the two capacitors are respectively and and their directions are both from the source and drain of the switching transistor to the input terminal of the BG_T<0> signal. Therefore, the equation is established as

[0044]

[0045] Since the operating state of the transistors in the bandgap reference source remains unchanged, the base voltage remains unchanged in the above two cases. In order to make the bandgap voltage V′ bg0 relative to V bg0 change in a direction as close as possible to the decreasing direction of VCC, so as to avoid oscillation, the two formulas (1) and (2) can be subtracted from both sides of the equation respectively, and then we get

[0046]

[0047] If the direction of change of the bandgap voltage V′ bg0 relative to V bg0 is as close as possible to the decreasing direction of VCC, then the term needs to be as small as possible, while the term needs to be as large as possible.

[0048] Therefore, it can be achieved by maximizing the ratio of the transient currents of each pole of the switching transistor in the trimming branch , or by maximizing the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch .

[0049] Preferably, the switching transistor corresponding to the trimming branch with the highest trimming probability in the trimming circuit is arranged at the module edge of the trimming circuit to achieve an increase in the ratio of the transient currents of the switching transistor .

[0050] To ensure the maximization of the ratio of the transient currents of the switching transistor , the usage probability of the switching transistors in multiple trimming branches is considered in the present invention. When the trimming range of the circuit is small, the switching transistor used the most must be the one with the highest trimming accuracy. That is, the switching transistor corresponding to the branch with the smallest resistance value in parallel with the switching transistor.

[0051] Preferably, the branch with the highest trimming accuracy among multiple trimming branches is arranged at the module edge of the trimming circuit; and, the size of the switching transistor in the adjustment branch is adjusted.

[0052] At this time, the switching transistor can be arranged at the edge of the module to facilitate the adjustment of the area of the switching transistor. Since the size of the switching transistor is closely related to the magnitude of the parasitic capacitance of the switching transistor, in the method of the present invention, the size of the switching transistor can be adjusted. For example, the size of its source electrode can be increased, and the size of the drain electrode can be decreased or remain unchanged, etc. In this way, a significant reduction in oscillation can be achieved.

[0053] Preferably, the trimming up-resistance is the resistance value of the equivalent resistance between the switching transistor closest to the pre-stabilized voltage output terminal and in the on state and the pre-stabilized voltage output terminal after the states of the switching transistors in multiple trimming branches are determined. The trimming down-resistance is the resistance value of the equivalent resistance between the switching transistor closest to the base of the transistor in the bandgap reference source and in the on state and the base of the transistor after the states of the switching transistors in multiple trimming branches are determined.

[0054] As described above, the calculation methods of the trimming up-resistance and the trimming down-resistance in the present invention can change accordingly according to the changes in the circuit. However, in order to maximize the value of, Figure 1 the resistor R1 in the circuit in down can be arranged below the trimming circuit and used as part of R down . In addition, a reference resistor R0 in the trimming circuit should also be arranged below the trimming circuit and used as part of R down . Since the resistance values of the resistors in multiple trimming branches are not completely the same, in order to increase the possibility of the value of R up , the circuit with the lowest trimming accuracy can be placed below, and the circuits with higher trimming accuracies can be placed above in sequence, making it more likely to become part of R

[0055] It should be noted that each trimming branch in the present invention may include a switching transistor and a resistor connected across the two ends of the switching transistor. When the resistance value of the resistor is smaller, the number of fingers of the switching transistor connected thereto can be increased. It can be understood that when the switching transistor is in parallel with the resistor, the larger the number of fingers of the switching transistor, the smaller the equivalent resistance Rds between the source and drain of the switching transistor when it is turned on. The trimming circuit is used to trim the value of Vbg by trimming the resistance value of the series resistors. For example, when the resistance is smaller, the larger the number of switching transistors in parallel with it, it can ensure that the equivalent resistance of the switching transistor is much smaller than the resistance value of its parallel resistor. After the two are in parallel, when the switching transistor is turned off, its resistance can be considered approximately equal to the size of the resistor, so as to approximately realize trimming Vbg by adding or subtracting the size of the resistor, rather than trimming Vbg by adding or subtracting the equivalent resistance after the resistor is in parallel with the switching transistor. On the other hand, this arrangement can also prevent a large amount of current flowing through the switching transistor in the conducting state from being shunted when the resistance is very small. In the embodiment of the present invention, the number of fingers of the switching transistor on the resistor with the highest trimming accuracy of 0.25R can be 32. As the resistance value increases, the number of fingers in the switching transistor can be reduced, so as to meet the requirement that the current between the source and drain of the switching transistor in the circuit is much larger than the current of the resistor.

[0056] Figure 3 It is a schematic diagram for analyzing the principle of avoiding oscillation of a trimming circuit of a bandgap reference source for reducing oscillation in the present invention. As Figure 3 shown, in the present invention, simulations are respectively carried out for the Figure 3 layout on the left side and the layout on the right side in Figures 4 to 7 , and the obtained simulation results are as Figure 4 and Figure 5 shown. Among them, Figure 6 and Figure 7 are the simulation results of the first embodiment of the present invention. During this simulation process, a load is added to the LDO, and the load current that causes an instantaneous drop in the pre-stabilized voltage is 10 mA. And

[0057] In addition, Figure 4 and Figure 7 the dashed lines in Figure 3The simulation result of the circuit in the prior art state on the left side, while the solid line is Figure 3 The simulation result of the improved circuit of the present invention on the right side.

[0058] Figure 4 It is a schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the first embodiment of a trimming circuit for a bandgap reference source with reduced oscillation in the present invention. As Figure 4 shown, in the prior art, when the pre-stabilization voltage instantaneously drops from about 4.745V to about 4.74V, the bandgap voltage Vbg undergoes a large oscillation, and its voltage rises from about 1.248V to 1.2486V, and the oscillation continues from 4.0ms to about 4.023ms before ending. However, after the improvement of the present invention, although the pre-stabilization voltage drops from 4.475V to about 4.739V, the oscillation basically ends before 4.01ms. In addition, the bandgap voltage Vbg basically does not oscillate at 4.0ms.

[0059] Figure 5 It is a high-precision schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the first embodiment of a trimming circuit for a bandgap reference source with reduced oscillation in the present invention. Figure 5 It is Figure 4 a high-precision partial schematic diagram. After improving the precision of the horizontal axis and the vertical axis in Figure 4 , it can be seen that the bandgap voltage Vbg only drops from about 1.24803V to about 1.24799V at 4.0ms, and recovers to about 1.24804V at about 4.003ms, and quickly returns to a stable state after 4.01ms.

[0060] Compared with the prior art, the method of the present invention reduces the maximum peak-to-valley value of the bandgap voltage during the pre-stabilization voltage settlement caused by a 10mA load current from 0.96mV to 45uV.

[0061] Figure 6 It is a schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the second embodiment of a trimming circuit for a bandgap reference source with reduced oscillation in the present invention. In the prior art, when a 100mA load current settlement occurs in VCC, causing VCC to drop from 4.744V to about 4.716V, VCC takes about 0.018ms to recover from the oscillation, and at this time the bandgap voltage Vbg rises from 1.248V to about 1.253V, and still cannot fully recover from the oscillation after 0.018ms. After the improvement of the circuit of the present invention, when VCC undergoes a settlement, the bandgap voltage Vbg only slightly drops from 1.248V to about 1.2476V, and only takes 0.004ms to fully recover from the oscillation.

[0062] Figure 7 This is a high-precision schematic diagram showing the variation of the pre-stabilization voltage and the bandgap voltage with time during the simulation of the second embodiment of the trimming circuit for a bandgap reference source that reduces oscillation in the present invention. As Figure 7 shown, in this case, the maximum peak-to-valley value of the bandgap voltage Vbg is reduced from 6.18 mV to 0.49 mV, and Vbg quickly returns to stability.

[0063] The beneficial effect of the present invention is that, compared with the prior art, the trimming circuit for a bandgap reference source that reduces oscillation in the present invention can rationally design the trimming module in the bandgap circuit according to the mutation direction of the output voltage of the pre-stabilization module under the working conditions of the circuit, thereby minimizing circuit oscillation and enabling the circuit to quickly stabilize.

[0064] The applicant of the present invention has made a detailed description and illustration of the embodiments of the present invention in conjunction with the accompanying drawings of the specification. However, those skilled in the art should understand that the above embodiments are only the preferred implementation schemes of the present invention, and the detailed description is only to help readers better understand the spirit of the present invention, rather than a limitation on the protection scope of the present invention. On the contrary, any improvement or modification made based on the spirit of the present invention should fall within the protection scope of the present invention.

Claims

1. A trimming circuit for a bandgap reference source to reduce oscillation, characterized in that: The circuit is connected between the device voltage terminal of the bandgap reference source and the pre-stabilized voltage output terminal; and the circuit includes a reference resistor and multiple trimming branches arranged in a preset order. Wherein, the preset order is set based on the oscillation direction when the pre-stabilized voltage oscillates. When the pre-stabilized voltage oscillates in a sudden drop manner, maximize the ratio of the transient currents of each pole of the switching transistor in the trimming branch Wherein, is the transient current of the parasitic capacitance between the gate and source of the switching transistor when it is in the on state during the pre-stable voltage dip; is the transient current of the parasitic capacitance between the gate and drain of the switching transistor when it is in the on state during the pre-stable voltage dip.

2. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 1, characterized in that: Arrange the switching transistor corresponding to the trimming branch with the highest trimming probability in the trimming circuit at the edge of the module of the trimming circuit to achieve the ratio of the transient currents of the switching transistors to increase.

3. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 2, characterized in that: The branch with the highest trimming accuracy among the multiple trimming branches is arranged at the edge of the module of the trimming circuit; and the size of the switching transistor in the branch is adjusted.

4. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 1, characterized in that: When the pre-stabilized voltage oscillates in a sudden drop manner, maximize the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch 5. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 4, characterized in that: The trimming up-resistance is the resistance value of the equivalent resistance between the switching transistor closest to the pre-stabilized voltage output terminal in the conducting state and the pre-stabilized voltage output terminal when the states of the switching transistors of the multiple trimming branches are determined.

6. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 4, characterized in that: The trimming down-resistance is the resistance value of the equivalent resistance between the switching transistor closest to the base of the transistor in the bandgap reference source in the conducting state and the base of the transistor when the states of the switching transistors of the multiple trimming branches are determined.

7. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 6, characterized in that: The reference resistor is directly connected to the device of the bandgap reference source and is connected to the pre-stabilized voltage output terminal through multiple trimming branches.

8. The trimming circuit for a bandgap reference source to reduce oscillation according to claim 1, characterized in that: The output terminal of the trimming circuit is connected to a low-dropout linear regulator (LDO).

9. The trimming circuit for a bandgap reference source to reduce oscillation according to any one of claims 1-8, characterized in that: Minimize the ratio of the transient currents of each pole of the switching transistor in the trimming branch when the pre-stabilized voltage oscillates in a sudden increase manner and the ratio of the trimming up-resistance to the trimming down-resistance in the trimming branch

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