Test device for low dropout linear regulator

Abstract

The present application discloses a test device for a low dropout linear regulator, comprising: a variable load module connected to the voltage output terminal of the low dropout linear regulator, and the low dropout linear regulator generates an output voltage according to the load value of the variable load module and outputs it at the voltage output terminal; a signal source for providing a pulse signal; a driving module for generating a driving signal according to the pulse signal; an adjustment transistor connected between the variable load module and the reference ground for adjusting the output current at the load end according to the driving signal; and a signal conditioning module for adjusting the conduction speed of the adjustment transistor by adjusting the rising edge speed of the pulse signal, thereby changing the change speed of the output current. The test device of the present application solves the problems of ringing and oscillation of the output voltage in the load transient response test, which is beneficial to improving the stability of the system.

Description

Technical Field

[0001] The present invention relates to the technical field of linear regulators, and more particularly, to a test device for a low dropout linear regulator. Background Art

[0002] A low dropout linear regulator (LDO) converts an unstable input voltage into an adjustable DC output voltage for use as a power supply for other systems. Due to the characteristics of simple structure, low static power consumption, and small output voltage ripple of linear regulators, linear regulators are often used for on-chip power management of mobile consumer electronic device chips.

[0003] As a complete functional module, some performance indicators must be considered during the design of an LDO. Only designs that meet the corresponding indicators can be finally applied to systems and products. The main performance indicators of an LDO include: input / output voltage difference, load driving ability, static current, power supply rejection ratio, efficiency, start-up time, load transient response, etc. During mass production, there are often certain deviations between the actual performance indicators of the LDO and the nominal values, resulting in inconsistencies between the theoretical and actual values. Such inconsistencies will increase the inconsistencies of the system or product. Therefore, the testing of the LDO plays a very important role in improving the consistency and stability of the entire circuit system.

[0004] The traditional method for testing the load transient response of an LDO is mainly to supply power to the LDO and its modules using a voltage source instrument, and gradually change the operating conditions of the LDO by adjusting the output voltage or load size to determine the performance of the LDO. As Figure 1 shown, in the traditional load transient response test method, when the load changes, the rise time of the output current Iout is short, which easily causes phenomena such as ringing and oscillation of the output voltage Vout. In addition, with the improvement of the performance of the LDO, the requirements for the test device for load transient response are also getting higher and higher, and the same product often has different test conditions, and the requirements for the system stability of the test device are also getting larger. Therefore, the traditional test device can no longer meet the requirements of existing LDO tests. Summary of the Invention

[0005] In view of the above problems, the purpose of the present invention is to provide a test device for a low dropout linear regulator, which can adjust the rise time of the output current during the load transient response test to avoid phenomena such as ringing or oscillation of the output voltage.

[0006] According to an embodiment of the present invention, a test device for a low dropout linear regulator is provided. The low dropout linear regulator includes a voltage input terminal and a voltage output terminal. Wherein, the test device includes: a variable load module connected to the voltage output terminal of the low dropout linear regulator. The low dropout linear regulator generates an output voltage according to the load value of the variable load module and outputs it at the voltage output terminal; a signal source for providing a pulse signal; a driving module for generating a driving signal according to the pulse signal; an adjustment transistor connected between the variable load module and the reference ground for adjusting the output current at the load end according to the driving signal; and a signal conditioning module for adjusting the conduction speed of the adjustment transistor by adjusting the rising edge speed of the pulse signal, thereby changing the change speed of the output current.

[0007] Optionally, the test device further includes: a DC voltage source connected between the voltage input terminal of the low dropout linear regulator and the reference ground, the DC voltage source is used to supply power to the low dropout linear regulator; an input capacitor connected between the voltage input terminal of the low dropout linear regulator and the reference ground; and an output capacitor connected between the voltage output terminal of the low dropout linear regulator and the reference ground.

[0008] Optionally, the driving module includes: a first transistor and a second transistor connected in sequence between the voltage input terminal of the low dropout linear regulator and the reference ground. The control terminals of the first transistor and the second transistor receive the pulse signal, and the intermediate node of the first transistor and the second transistor outputs the driving signal.

[0009] Optionally, the signal conditioning module includes: a variable resistor, the first end of the variable resistor is connected to the output terminal of the signal source, and the second end is connected to the control terminals of the first transistor and the second transistor.

[0010] Optionally, the signal conditioning module further includes: a variable capacitor connected between the control terminal of the adjustment transistor and the reference ground.

[0011] Optionally, the variable load module includes: a first variable load resistor, the first end of the first variable load resistor is connected to the voltage output terminal of the low dropout linear regulator, and the second end is connected to the first end of the adjustment transistor; and a second variable load resistor, the first end of the second variable load resistor is connected to the voltage output terminal of the low dropout linear regulator, and the second end is connected to the reference ground.

[0012] Optionally, the adjustment transistor is selected from an N-type metal oxide semiconductor field effect transistor.

[0013] Optionally, the first transistor is selected from NPN bipolar transistors, and the second transistor is selected from PNP bipolar transistors.

[0014] The test device for a low dropout linear regulator according to an embodiment of the present invention includes: a variable load module connected to the voltage output terminal of the low dropout linear regulator, where the low dropout linear regulator generates an output voltage according to the load value of the variable load module and outputs it at the voltage output terminal; a signal source for providing a pulse signal; a driving module for generating a driving signal according to the pulse signal; an adjustment transistor connected between the variable load module and the reference ground for adjusting the output current at the load end according to the driving signal; and a signal conditioning module for adjusting the conduction speed of the adjustment transistor by adjusting the rising edge speed of the pulse signal, thereby changing the change speed of the output current. The test device according to the embodiment of the present invention solves the problems of ringing and oscillation of the output voltage in the load transient response test, which is beneficial to improving the stability of the system. In addition, the test device according to the embodiment of the present invention can provide different test conditions and is applicable to the test of higher performance low dropout linear regulators. Description of the Drawings

[0015] Through the following description of the embodiments of the present invention with reference to the drawings, the above and other objects, features, and advantages of the present invention will become clearer. In the drawings:

[0016] Figure 1 A voltage schematic diagram of the output current and output voltage during the load transient response test of a conventional LDO is shown;

[0017] Figure 2 A circuit schematic diagram of the test device for a low dropout linear regulator according to an embodiment of the present invention is shown;

[0018] Figure 3 A voltage schematic diagram of the output current and output voltage during the load transient response test of an existing test device for a low dropout linear regulator is shown;

[0019] Figure 4 A voltage schematic diagram of the output current and output voltage during the load transient response test of the test device for a low dropout linear regulator according to an embodiment of the present invention is shown. Detailed Embodiments

[0020] The various embodiments of the present invention will be described in more detail below with reference to the drawings. In each drawing, the same elements are denoted by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0021] It should be understood that in the following description, a "circuit" refers to a conductive loop formed by at least one component or sub-circuit through electrical connection or electromagnetic connection. When an element or circuit is said to be "connected to" another element or when an element / circuit is said to be "connected between" two nodes, it can be directly coupled or connected to another element or there may be intermediate elements. The connection between elements can be physical, logical, or a combination thereof. On the contrary, when an element is said to be "directly coupled to" or "directly connected to" another element, it means there are no intermediate elements between the two.

[0022] In the present application, a MOSFET includes a first terminal, a second terminal, and a control terminal. In the on-state of the MOSFET, current flows from the first terminal to the second terminal. The first terminal, the second terminal, and the control terminal of a P-type MOSFET are the source, the drain, and the gate respectively, and the first terminal, the second terminal, and the control terminal of an N-type MOSFET are the drain, the source, and the gate respectively. A bipolar transistor includes a first terminal, a second terminal, and a control terminal. In the on-state of the bipolar transistor, current flows from the first terminal to the second terminal. The first terminal, the second terminal, and the control terminal of a PNP-type bipolar transistor are the emitter, the collector, and the base respectively, and the first terminal, the second terminal, and the control terminal of an NPN-type bipolar transistor are the collector, the emitter, and the base respectively.

[0023] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0024] Figure 2 A circuit schematic diagram of a test device for a low dropout linear regulator according to an embodiment of the present invention is shown. As Figure 2 shown, the test device includes a signal source 110, a driving module 120, an adjusting transistor Q1, and a variable load module 130. The variable load module 130 is connected to the voltage output terminal of the low dropout linear regulator 200, and the low dropout linear regulator 200 generates an output voltage according to the load value of the variable load module 130 and outputs it at the voltage output terminal. The signal source 110 is used to provide a pulse signal, the driving module 120 is used to generate a driving signal according to the pulse signal, and the adjusting transistor Q1 is connected between the variable load module 130 and the reference ground, and is used to adjust the output current at the load end according to the driving signal.

[0025] Among them, the test device 100 further includes a signal conditioning module, and the signal conditioning module adjusts the conduction speed of the adjusting transistor Q1 by adjusting the rising edge speed of the pulse signal, thereby changing the change speed of the output current at the load end.

[0026] Further, the test device 100 further includes a DC voltage source DC, an input capacitor Cin, and an output capacitor Cout. The DC voltage source DC is connected between the voltage input terminal of the low-dropout linear regulator 200 and the reference ground, and the DC voltage source DC is used to supply power to the low-dropout linear regulator 200. The input capacitor Cin and the output capacitor Cout are respectively connected between the voltage input terminal of the low-dropout linear regulator 200 and the reference ground and between the voltage output terminal of the low-dropout linear regulator 200 and the reference ground.

[0027] Further, the driving module 120 includes transistors P1 and P2. The transistors P1 and P2 are sequentially connected between the voltage input terminal of the low-dropout linear regulator 200 and the reference ground. The control terminals of the transistors P1 and P2 receive the pulse signal, and the intermediate node of the transistors P1 and P2 outputs the driving signal.

[0028] Further, the signal conditioning module includes a variable resistor Rs and / or a variable capacitor C1. The first end of the variable resistor Rs is connected to the output terminal of the signal source 110, the second end is connected to the control terminals of the transistors P1 and P2, and the variable capacitor C1 is connected between the control terminal of the regulating transistor Q1 and the reference ground.

[0029] Further, the variable load module 130 includes: a first variable load resistor R1 and a second variable load resistor R2. The first end of the first variable load resistor R1 is connected to the voltage output terminal of the low-dropout linear regulator 200, the second end is connected to the first end of the regulating transistor Q1, and the first end of the second variable load resistor R2 is connected to the voltage output terminal of the low-dropout linear regulator 200, and the second end is connected to the reference ground. Among them, the first variable load resistor R1 is a dynamic variable load resistor, and the second variable load resistor R2 is a static variable load resistor. Therefore, by adjusting the resistance values of the first variable load resistor R1 and the second variable load resistor R2, any combination of dynamic load and static load can be obtained.

[0030] Further, the regulating transistor Q1 is, for example, selected from N-type MOSFETs, the transistor P1 is, for example, selected from NPN-type bipolar transistors, and the transistor P2 is, for example, selected from PNP-type bipolar transistors. When the pulse signal provided by the signal source 110 is a logic high level, the transistor P1 is turned on, the transistor P2 is turned off, and the regulating transistor Q1 is turned on to provide the output current required for testing. At this time, the RC circuit composed of the variable resistor Rs and the variable capacitor C1 can slow down the turn-on speed of the regulating transistor Q1, thereby making the system more stable; when the pulse signal provided by the signal source 110 is a logic low level, the transistor P1 is turned off, the transistor P2 is turned on, and the control terminal of the regulating transistor Q1 discharges to the ground through the transistor P2, which can make the turn-off speed of the regulating transistor Q1 faster and reduce the switching loss.

[0031] During the conduction process of the adjustment transistor Q1, the rising time of the output current can be changed by changing the resistance value of the variable resistor Rs or the capacitance value of the variable capacitor C1. Since the rising speed of the pulse signal provided by the signal source 110 is constant, if the capacitance value of the variable capacitor C1 remains unchanged, the smaller the resistance value of the variable resistor Rs, the shorter the rising time of the pulse signal, and the faster the rising speed of the current at the load end. The larger the resistance value of the variable resistor Rs, the longer the rising time of the pulse signal, and the slower the rising speed of the current at the load end. Similarly, if the resistance value of the variable resistor Rs remains unchanged, the smaller the capacitance value of the variable capacitor C1, the shorter the rising time of the pulse signal, and the faster the rising speed of the current at the load end. The larger the capacitance value of the variable capacitor C1, the longer the rising time of the pulse signal, and the slower the rising speed of the current at the load end.

[0032] Figure 3 And Figure 4 respectively show the voltage schematic diagrams of the output current and output voltage during the load transient response test of the test device of the existing low-dropout linear regulator and the test device of the low-dropout linear regulator according to the embodiment of the present invention. Among them, Figure 3 And Figure 4 the dotted lines in represent the output voltage Vout, and the solid lines represent the output current Iout. As Figure 4 shown, by increasing the resistance value of the variable resistor Rs, the rising time of the output current Iout during the load transient response test can be increased from 200 ns to 500 ns. At the same time, no phenomena such as glitches and ringing occur in the output voltage Vout during this process. Therefore, the test device of the present invention can solve the problems of ringing and oscillation of the output voltage in the load transient response test, improve the stability of the system, and is applicable to the test of higher-performance low-dropout linear regulators.

[0033] In summary, the test device of the low-dropout linear regulator according to the embodiment of the present invention includes: a variable load module connected to the voltage output end of the low-dropout linear regulator, and the low-dropout linear regulator generates an output voltage according to the load value of the variable load module and outputs it at the voltage output end; a signal source for providing a pulse signal; a driving module for generating a driving signal according to the pulse signal; an adjustment transistor connected between the variable load module and the reference ground for adjusting the output current at the load end according to the driving signal; and a signal conditioning module for adjusting the conduction speed of the adjustment transistor by adjusting the rising edge speed of the pulse signal, thereby changing the change speed of the output current. The test device of the embodiment of the present invention solves the problems of ringing and oscillation of the output voltage in the load transient response test, which is beneficial to improving the stability of the system. In addition, the test device of the embodiment of the present invention can provide different test conditions and is applicable to the test of higher-performance low-dropout linear regulators.

[0034] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or further includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising an..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0035] According to the embodiments of the present invention as described above, these embodiments do not describe all the details in detail, nor do they limit the invention to only the specific embodiments. Obviously, according to the above description, many modifications and variations can be made. These embodiments are selected and specifically described in this specification in order to better explain the principles and practical applications of the present invention, so that those skilled in the art can make good use of the present invention and its modified use based on the present invention. The protection scope of the present invention shall be subject to the scope defined by the claims of the present invention.

Claims

1. A test device for a low dropout linear regulator, the low dropout linear regulator including a voltage input terminal and a voltage output terminal, wherein, The test device includes: a variable load module connected to the voltage output terminal of the low dropout linear regulator, where the low dropout linear regulator generates an output voltage according to the load value of the variable load module and outputs it at the voltage output terminal; a signal source for providing a pulse signal; a driving module for generating a driving signal according to the pulse signal; an adjustment transistor connected between the variable load module and the reference ground for adjusting the output current at the load end according to the driving signal; and a signal conditioning module for adjusting the conduction speed of the adjustment transistor by adjusting the rising edge speed of the pulse signal, thereby changing the change speed of the output current, wherein the signal conditioning module includes a variable resistor and / or a variable capacitor, a first end of the variable resistor is connected to the output terminal of the signal source, a second end is connected to the driving module, the variable capacitor is connected between the control terminal of the adjustment transistor and the reference ground, and the rising speed of the output current is changed by changing the resistance value of the variable resistor or the capacitance value of the variable capacitor during the conduction process of the adjustment transistor.

2. The test device according to claim 1, wherein, It further includes: a DC voltage source connected between the voltage input terminal of the low dropout linear regulator and the reference ground, and the DC voltage source is used to supply power to the low dropout linear regulator; an input capacitor connected between the voltage input terminal of the low dropout linear regulator and the reference ground; and an output capacitor connected between the voltage output terminal of the low dropout linear regulator and the reference ground.

3. The test device according to claim 2, wherein, The driving module includes: a first transistor and a second transistor connected in sequence between the voltage input terminal of the low dropout linear regulator and the reference ground, control terminals of the first transistor and the second transistor receive the pulse signal, and an intermediate node of the first transistor and the second transistor outputs the driving signal.

4. The test device according to claim 1, wherein, The variable load module includes: a first variable load resistor, a first end of the first variable load resistor is connected to the voltage output terminal of the low dropout linear regulator, and a second end is connected to a first end of the adjustment transistor; and a second variable load resistor, a first end of the second variable load resistor is connected to the voltage output terminal of the low dropout linear regulator, and a second end is connected to the reference ground.

5. The test device according to claim 1, wherein, The adjustment transistor is selected from N-type metal oxide semiconductor field effect transistors.

6. The test device according to claim 3, wherein, The first transistor is selected from NPN-type bipolar transistors, and the second transistor is selected from PNP-type bipolar transistors.

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