Simple over-temperature protection circuit capable of resisting process fluctuation in operational amplifier

Abstract

The invention belongs to the field of integrated circuits, and particularly relates to an anti-process-fluctuation simple over-temperature protection circuit in an operational amplifier, which is characterized in that for the operational amplifier with output capacity, a reference voltage generated by a reference circuit is compared with an output level of the over-temperature protection circuit, so that a control turn-off signal is obtained; an overheating turn-off function is implemented on the circuit, and reference current generated by the reference circuit is processed by the bias circuit and then provides bias current for the over-temperature protection circuit.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuits and relates to an over-temperature protection circuit for operational amplifiers, specifically a simple over-temperature protection circuit for operational amplifiers to resist process fluctuations. Background Technology

[0002] For operational amplifiers with a certain driving capability, the increased output current when driving high-current or large-capacitive loads leads to a significant increase in power consumption. Due to cost considerations and the demands of modern advanced packaging technology, the design of operational amplifiers often requires minimizing the chip area. Smaller chip area and smaller package size result in a significant increase in package thermal resistance. Therefore, as power consumption increases, the junction temperature of the operational amplifier rises rapidly. Once the limit is exceeded, it can lead to functional degradation or even burnout. Thus, a simple over-temperature protection circuit has become one of the protection methods integrated internally into operational amplifiers, offering advantages such as simple structure, ease of integration, and small area.

[0003] Existing simple over-temperature protection circuits typically utilize the PTAT current generated by the operational amplifier reference to produce an over-temperature protection signal. Common methods include allowing the PTAT current to flow through a resistor, generating a voltage signal that is compared with a reference voltage to generate the over-temperature protection signal; or using the PTAT current to flow through a resistor and a negative-temperature element (such as a diode, a transistor's BE junction, or a gate-drain shorted MOSFET), comparing the resulting voltages to generate the over-temperature protection signal. The over-temperature protection signal then passes through logic circuitry to control the operational amplifier's on / off state.

[0004] However, relying solely on the temperature coefficient of a single device results in a relatively small voltage change, which can easily lead to drift and false triggering of the over-temperature protection point. Furthermore, both the operational amplifier's reference and the over-temperature protection circuit are affected by process variations. Changes in process doping, dimensional errors, and other factors can significantly impact the operation of the over-temperature protection circuit, causing the over-temperature protection point to shift, resulting in over-temperature protection failure or premature triggering at operating temperature. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a simple over-temperature protection circuit for operational amplifiers to resist process fluctuations. The circuit includes comparing the reference voltage generated by the reference circuit with the output level of the over-temperature protection circuit for operational amplifiers with output capability, thereby obtaining a control shutdown signal to implement the overheat shutdown function of the circuit. The reference current generated by the reference circuit is processed by the bias circuit to provide bias current for the over-temperature protection circuit.

[0006] This invention provides a simple over-temperature protection circuit for operational amplifiers to resist process fluctuations. It achieves stable over-temperature protection with a simple structure and a small layout area, and is not easily affected by process fluctuations. Attached Figure Description

[0007] Figure 1 This is a schematic diagram illustrating the over-temperature protection circuit technology of the present invention;

[0008] Figure 2 This is a schematic diagram of the over-temperature protection circuit of the present invention;

[0009] Figure 3 This is a schematic diagram illustrating an application example of the over-temperature protection circuit of the present invention;

[0010] Figure 4 The marking voltage V of this invention BG and V OT Temperature characteristic graph;

[0011] Figure 5 This is a schematic diagram illustrating the over-temperature protection point of the present invention as it fluctuates with the process. Detailed Implementation

[0012] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0013] This invention proposes a simple over-temperature protection circuit for operational amplifiers to resist process fluctuations. The reference current generated by the reference circuit is used to generate a bias current through the bias circuit to power the over-temperature protection circuit. The over-temperature level output by the over-temperature protection circuit is shaped by the logic circuit to obtain a shutdown control signal. The shutdown control signal is used to control the on and off functions of the main operational amplifier according to the temperature.

[0014] For operational amplifiers with a certain output capability, a reference voltage generated by a reference is compared with the output level of an over-temperature protection circuit to obtain a control shutdown signal, thereby implementing an over-temperature shutdown function for the circuit. The technical approach of this invention's circuit is as follows: Figure 1 As shown, the reference circuit generates a reference current I. BG and reference voltage V BG Reference current I BG The over-temperature protection circuit is powered by the bias circuit, thereby generating the over-temperature output level V. OT Over-temperature output level V OT With reference voltage V BGThe comparison is then performed, and the signal is shaped by a logic circuit (inverter) to obtain the shutdown control signal V. EN This controls the on / off function of the main operational amplifier module.

[0015] The simple over-temperature protection structure of this invention is as follows: Figure 2 As shown, it can be compatible with any operational amplifier's PTAT reference source, which generates the reference current I. BG By introducing a first MOSFET M1 with its gate and drain shorted and a first resistor R1, a reference voltage V is obtained. BG At this time, the reference voltage V BG This is a voltage with a positive temperature coefficient. The main circuit of the over-temperature protection structure consists of six devices. The second MOSFET M2 and the second resistor R2, and the first MOSFET M1 and the first resistor R1 use similar structures to ensure similar susceptibility to temperature and process variations. The bias current I generated by the bias circuit... B From the reference current I BG Generated by a current mirror, i.e., I B =I BG And bias current I B The circuit is divided into two paths: one using the first transistor Q1 and the fifth MOSFET M5, and the other using the fourth MOSFET M4. The fourth MOSFET M4 and the third MOSFET M3 form a current mirror structure, making the current I2 generated by the fourth MOSFET M4 equal to the current I3 generated by the third MOSFET M3. At this time, current I3 flows through the second MOSFET M2 and the second resistor R2, resulting in an over-temperature output level V. OT The gate length L of the fourth MOSFET M4 is much larger than that of the fifth MOSFET M5. This results in the current I1 flowing through the fifth MOSFET and the first transistor Q1 at room temperature and under normal process conditions being much smaller than the current I2. Therefore, I3 = I2 ≈ I B ≈I BG By adjusting the parameters of the second MOSFET M2 and the second resistor R2, V can be obtained. OT >V BG At this time, the over-temperature protection function is not activated.

[0016] As temperature increases, the parameters of single-transistor devices are affected by temperature. The series connection of the fifth MOSFET M5 and the first transistor Q1 is more sensitive to temperature than that of the fourth MOSFET M4, causing the current I1 to increase rapidly, resulting in a higher current I1. B The proportion of current supplied to current I2 decreases, which in turn leads to a decrease in current I3 and voltage V. OT Then it decreases accordingly; causing the voltage V OT Voltage exhibiting a negative temperature coefficient, and voltage V exhibiting a positive temperature coefficient. BG After comparison by comparator C1, when voltage V OTDescending to V OT =V BG If the temperature rises further, comparator C1 will flip, ultimately activating the over-temperature protection function via the enable voltage V. EN The control switching device shuts down the main operational amplifier, rapidly reducing power consumption and protecting the circuit.

[0017] Figure 3 This diagram illustrates the actual over-temperature protection circuit structure in a typical operational amplifier, involving the reference for generating the PTAT current and the over-temperature protection function module. The operational amplifier's reference in the diagram consists of the 8:1 ratio of the third transistor Q3 and the fourth transistor Q4, and the ΔV... BE The fourth resistor R4 connects to the base of the fourth transistor Q4 and the base of the third transistor Q3, respectively. The internal amplifier A1 clamps the collectors of both transistors Q3 and Q4 to the same voltage. Simultaneously, the resistance of the third resistor R3 equals the resistance of the fourth resistor R4, resulting in equal currents in transistors Q3 and Q4, thus generating a PTAT current. The output of amplifier A1 feeds back to the gate of the sixth MOSFET M6, causing it to conduct and generate current, which is distributed to the fifth resistor R5 and the fifth transistor Q5 via two separate paths. The reference voltage V... BG The voltage difference generated by the PTAT current flowing through the fifth resistor R5 and the sixth resistor R6, as well as the voltage V of the fourth transistor Q4, are then determined. BE This is generated by superposition, while the reference current I... BG Then, based on the voltage V BG The voltage is generated through the fifth transistor Q5, the seventh MOSFET M7, and the seventh resistor R7.

[0018] The core of this invention lies in the fact that, in addition to its advantages of simple structure, small area, and low cost, its over-temperature protection function is not easily affected by process fluctuations. This is achieved through two aspects: first, by utilizing the series connection of the first transistor Q1 and the fifth MOSFET M5 to share the bias current I with the fourth MOSFET M4. B While obtaining the negative temperature coefficient current I2, the difference between the characteristics of the first transistor Q1 and the fifth MOSFET M5 connected in series and the characteristics of the fourth MOSFET M4 can be utilized. The current I1 will change with process fluctuations, and its trend is similar to that of the current I... B The trends of change are the same, but because I2=I B – I1 can eliminate some of the effects of process fluctuations in current I2; secondly, voltage V BG and voltage V OT The generation of V is due to the similar structure of the first MOSFET M1, the first resistor R1, and the second MOSFET M2 and the second resistor R2, which makes the voltage level V... BG and level V OTThe trends of change converge, which to some extent eliminates the large differences in comparator output caused by process fluctuations. In summary, through these two aspects of design, a simple over-temperature protection structure resistant to process fluctuations can be obtained. The entire structure uses only a few components to achieve stable and effective over-temperature protection.

[0019] Figure 4 The reference voltage V was shown. BG and over-temperature output level V OT Temperature characteristic curve, reference voltage V BG The positive temperature coefficient voltage generated by the standard PTAT current, and the over-temperature output level V. OT The initial stage is also affected by the PTAT current, exhibiting a positive temperature coefficient. This ensures that the over-temperature protection function will not falsely activate under normal and low-temperature operating conditions, thus preventing the operational amplifier's function from being affected. However, as the temperature increases, due to the current distribution effect of currents I1 and I2, current I3 decreases rapidly at high temperatures, causing the voltage level V to... OT It rapidly transforms into a negative temperature coefficient voltage, thus, as the temperature further increases, it correlates with the voltage level V. BG When the voltage relationship changes, the signal is flipped after comparison by the comparator, thus outputting the enable control signal V. EN Over-temperature protection is provided for the operational amplifier.

[0020] Figure 5 This study demonstrates the over-temperature protection structure's ability to withstand process fluctuations. The structure utilizes MOS devices, NPN devices, and resistors. Simulations of their biasing process angles were performed to characterize the impact of process fluctuations. T represents Typical, S represents Slow, and F represents Fast, representing the biasing process angles for MOS and NPN devices. T, Max, and Min represent the biasing process angles for the resistors. Combinations of these three device process angles resulted in 15 different typical process states to simulate the effects of process fluctuations. The final change in the over-temperature protection point is shown below. Figure 5 As shown in the figure, the over-temperature protection point under typical conditions is 144.3℃. However, under extreme process fluctuations, the over-temperature protection point falls on both sides of the typical condition, with extreme over-temperature protection points of 139.5℃ and 148.6℃ respectively. This shows that even under severe process fluctuations, the overall error of the over-temperature protection function is within ±5℃, demonstrating strong resistance to process fluctuations.

[0021] The above-described embodiments further illustrate the purpose, technical solution, and advantages of the present invention. It should be understood that the above-described embodiments are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made to the present invention within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A simple over-temperature protection circuit for operational amplifiers to resist process fluctuations, characterized in that, For an operational amplifier with a certain output capability, the reference voltage generated by the reference circuit is compared with the output level of the over-temperature protection circuit to obtain a control shutdown signal and implement the over-temperature shutdown function of the circuit. The reference current generated by the reference circuit is processed by the bias circuit to provide bias current for the over-temperature protection circuit.

2. The simplified over-temperature protection circuit for operational amplifiers against process fluctuations according to claim 1, characterized in that, The logic circuit includes a comparator and an inverter. The over-temperature level is used as the positive input terminal of the comparator, and the reference voltage generated by the reference circuit is used as the negative input terminal of the comparator. The output terminal of the comparator is processed by the inverter and outputs a shutdown control signal.

3. A simple over-temperature protection circuit for operational amplifiers to resist process fluctuations according to claim 2, characterized in that, The reference current passes sequentially through an N-type MOSFET with its gate shorted and a resistor to obtain the reference voltage.

4. A simple over-temperature protection circuit for operational amplifiers to resist process fluctuations according to claim 1, characterized in that, The reference current generates a bias current through the current mirror.

5. A simple over-temperature protection circuit for operational amplifiers against process fluctuations according to claim 1, characterized in that, The bias current is divided into two paths. The first path flows through the first transistor and the fifth MOSFET, and the second path flows through the fourth MOSFET. The current flowing through the fourth MOSFET is replicated by the current mirror structure formed by the third MOSFET and the fourth MOSFET. The replicated current flows through an N-type MOSFET with its gate shorted and a resistor to obtain the reference voltage.

6. A simple over-temperature protection circuit for operational amplifiers against process fluctuations according to claim 5, characterized in that, The over-temperature protection circuit includes a second MOSFET, a third MOSFET, a fourth MOSFET, a fifth MOSFET, a first transistor, and a second resistor, wherein: The source of the second MOSFET is connected to one end of the second resistor. The gate and drain of the second MOSFET and the drain of the third MOSFET are connected together as the output terminal of the over-temperature protection circuit. The source of the third MOSFET, the source of the fourth MOSFET, the base and collector of the first MOSFET are connected to the power supply terminal; the gate of the third MOSFET, the gate and source of the fourth MOSFET, and the gate and source of the fifth MOSFET are connected together and connected to the bias current terminal. The emitter of the first transistor is connected to the source of the fifth MOSFET.

7. A simple over-temperature protection circuit for operational amplifiers against process fluctuations according to claim 6, characterized in that, The second MOSFET is an N-type MOSFET, while the third, fourth, and fifth MOSFETs are P-type MOSFETs.

8. A simple over-temperature protection circuit for operational amplifiers against process fluctuations according to claim 5 or 6, characterized in that, The gate length L of the fifth MOSFET is greater than that of the fourth MOSFET, so that the current flowing through the first and fifth MOSFETs at room temperature is more than an order of magnitude lower than the current flowing through the fourth MOSFET.

9. A simple over-temperature protection circuit for operational amplifiers against process fluctuations according to claim 8, characterized in that, Adjust the parameters of the second MOSFET and the second resistor so that the over-temperature protection circuit outputs a higher over-temperature level than the reference level output by the reference circuit under normal temperature conditions. At this time, the over-temperature protection function is turned off. As the temperature rises during use, the over-temperature protection circuit outputs a lower over-temperature level. The over-temperature protection function is turned on when the output level of the over-temperature protection circuit equals the reference level.

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