CN109375701B

CN109375701B - Reference voltage reference source of multiplexed output

Info

Publication number: CN109375701B
Application number: CN201811594954.4A
Authority: CN
Inventors: 王晗; 林鹤
Original assignee: Anhui Xilei Electronic Technology Co ltd
Current assignee: Anhui Xilei Electronic Technology Co ltd
Priority date: 2018-09-19
Filing date: 2018-12-25
Publication date: 2020-12-22
Anticipated expiration: 2038-12-25
Also published as: CN109375701A

Abstract

The invention provides a reference voltage reference source with multi-path output, which is characterized in that: the reference voltage reference source comprises a first current source, a second current source, first to sixth transistors and a voltage adjusting element; the output of the first current source is connected with the input end of the first transistor, the output of the second current source is connected with the input end of the second transistor, the control end of the first transistor is connected with the control end of the second transistor, and the input end of the first transistor is also connected with the control end of the first transistor and provides a first reference voltage output; the output end of the first transistor is connected with the input end of the third transistor, the input end of the third transistor is connected with the control end of the third transistor, the output end of the third transistor is connected with the input end of the fourth transistor, the input end of the fourth transistor is connected with the control end of the fourth transistor, and the output end of the fourth transistor is grounded; the output end of the second transistor is connected with the input end of the fifth transistor through a voltage adjusting element, the input end of the fifth transistor is connected with the control end of the fifth transistor and provides a second reference voltage output, the output end of the fifth transistor is connected with the input end of the sixth transistor, the input end of the sixth transistor is connected with the control end of the sixth transistor, and the output end of the sixth transistor is grounded. The invention can provide two paths of different output reference voltages at the same time, not only reduces the extra area and power consumption brought by a multi-path reference voltage reference source, but also has simple structure and extremely low required current.

Description

Reference voltage reference source of multiplexed output

Technical Field

The invention relates to the field of power supply circuits, in particular to a reference voltage reference source with multiplexed output.

Background

The domestic mobile phone market is developing vigorously, according to the research of the research institute of the high-industry lithium battery industry, the goods output of the Chinese mobile phone reaches 12.5 hundred million in 2012, and the market scale of the lithium battery of the mobile phone reaches 232 million yuan (including PACK). The mobile phone basically uses lithium ion batteries, which can be made into flat rectangles, cylinders, rectangles, buckles and the like according to the requirements of different electronic products, and a plurality of batteries can be connected in series and in parallel to form a battery pack. The rated voltage of a lithium ion battery is generally 3.7V due to the change of materials, and the rated voltage of a lithium iron phosphate (hereinafter referred to as ferrophosphorus) positive electrode is 3.2V. The final charging voltage at full charge is typically 4.2V and the ferrophosphorus is 3.65V. The final discharge voltage of the lithium ion battery is 2.75V-3.0V (the working voltage range or the final discharge voltage is given by a battery factory, and each parameter is slightly different, generally 3.0V, and ferrophosphorus is 2.5V). Generally, the voltage output range of lithium battery is about 3.0V to 4.2V, and the voltage variation range is about 40%, and such a large voltage variation range puts high requirements on the chip or module connected with the battery for supplying power.

In a cellular phone, a significant number of chips or internal circuits are directly powered by batteries (e.g., rf front-end circuits, power amplifiers, rf switches, etc.). Due to the wide variation range of the directly connected battery voltage, it is often necessary to convert the input voltage of 3.0V to 4.2V to a fixed voltage (e.g. 1.8V or 1.2V) lower than 3.0V by using a reference voltage reference source capable of withstanding a higher power supply voltage. The method has the advantages that the linear voltage stabilizer can bear the power supply voltage with a large variation range and keep the output voltage amplitude unchanged, so that the requirements of other internal circuits on the variation range of the power supply voltage are greatly reduced, and the circuit implementation is simplified.

With the rapid development of the internet of things market, the number and market share of wearable electronic devices are also rapidly increased, and the rise of consumer applications such as smart watches, smart bracelets and wireless earphones promotes the fire heat of the wearable market. In wireless electronic products such as watches, bracelets and earphones, the power consumption of a chip is strictly required, and wearable equipment objectively requires lighter equipment weight and longer standby time and working time. The requirement of low power consumption is urgent relative to other electronic product markets, and a plurality of power supply voltages are often needed in a complex SoC chip inside a product to provide normal operation of functional modules of different power domains, so that a plurality of reference voltage reference sources are often needed to provide different reference voltages which do not change along with changes of temperature and power supply voltage. The placement of multiple reference voltage reference sources would require additional area and power consumption and result in a geometrically enhanced complexity of the design.

Fig. 1 shows a conventional bandgap reference voltage circuit, which mainly comprises two parts: the core circuit adopts a resistor and a triode to respectively generate two paths of voltages with positive temperature coefficients and negative temperature coefficients and add the two paths of voltages to obtain output reference voltage, so that the positive temperature coefficients and the negative temperature coefficients are completely counteracted, and the output reference voltage is unrelated to temperature; and a current mirror structure is adopted above the resistor and the triode so as to eliminate the influence of power supply voltage fluctuation on output voltage. The reference voltage circuit can generate a reference voltage of about 1.2V, the voltage is directly dependent on the band gap voltage of silicon, the variation amplitude is small, but only one output is provided, and therefore, an additional linear transformer and the like are needed to provide other reference voltages.

Therefore, the structure and the number of the reference voltage reference sources are required to be reduced to meet the requirements of low power consumption and miniaturization in practical application.

Disclosure of Invention

In order to overcome the defects in the prior art, the invention provides a novel reference voltage reference source which has the advantages of multi-path output and simple circuit structure, can effectively reduce the power consumption and the number of reference sources, and can be applied to ultra-low power consumption application in the field of various consumer electronics.

In order to achieve the object of the present invention, the present invention provides a reference voltage reference source with multiple outputs, which is characterized in that: the reference voltage reference source includes a first current source (I1) and a second current source (I2), first to sixth transistors (NM1-NM6), a voltage adjustment element; wherein,

the output of the first current source is connected with the input end of the first transistor, the output of the second current source is connected with the input end of the second transistor, the control end of the first transistor is connected with the control end of the second transistor, and the input end of the first transistor is also connected with the control end of the first transistor and provides a first reference voltage output; the output end of the first transistor is connected with the input end of the third transistor, the input end of the third transistor is connected with the control end of the third transistor, the output end of the third transistor is connected with the input end of the fourth transistor, the input end of the fourth transistor is connected with the control end of the fourth transistor, and the output end of the fourth transistor is grounded;

the output end of the second transistor is connected with the input end of the fifth transistor through a voltage adjusting element, the input end of the fifth transistor is connected with the control end of the fifth transistor and provides a second reference voltage output, the output end of the fifth transistor is connected with the input end of the sixth transistor, the input end of the sixth transistor is connected with the control end of the sixth transistor, and the output end of the sixth transistor is grounded.

Further, the currents of the first current source and the second current source are equal, and the first current source and the second current source are implemented by adopting a current mirror.

Further, the voltage adjusting element is a regulating resistor.

Further, the voltage adjustment element is a series combination of a resistor and a diode, and the diode is connected between the output end of the second transistor and the input end of the fifth transistor in a forward direction.

The first transistor, the second transistor, the third transistor and the fourth transistor adopt NMOS tubes; the NMOS transistor also has a body electrode connected to ground to further reduce the noise of the circuit.

Further, the first reference voltage is 1.8V, and the second reference voltage is 1.2V.

The reference voltage circuit of the invention adopts a single reference voltage reference source, can provide two different output reference voltages at the same time, and the two output reference voltages do not change along with the fluctuation of temperature and power supply voltage; meanwhile, the extra area and power consumption brought by the multi-path reference voltage reference source are reduced, the structure is simple, and the required current is extremely low. Compared with the traditional circuit structure, the circuit design is simplified, meanwhile, the ultra-low power consumption application is realized, the manufacturing cost is saved, and the circuit is very suitable for the reference voltage reference source of the SoC chip in the wearable equipment.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

Drawings

The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the example serve to explain the principles of the invention and not to limit the invention.

FIG. 1 is a prior art bandgap reference voltage circuit;

FIG. 2 is a circuit diagram of a multi-output reference voltage reference source according to an embodiment of the present invention;

fig. 3 is a graph of a simulation of the output of the reference voltage reference source shown in fig. 2.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. It should be noted that the embodiments and features of the embodiments in the present application may be arbitrarily combined with each other without conflict.

The bandgap reference voltage circuit shown in fig. 1 can only provide a reference voltage output of about 1.2V, which is directly dependent on the bandgap voltage of silicon. When the requirement of multiple reference voltages is met, an additional linear transformer or a reference voltage reference circuit is often needed to provide other reference voltages, which results in the increase of the volume and power consumption of the device.

In order to overcome the defects, the invention provides a reference voltage source with multi-path output. Fig. 2 shows a reference voltage reference source circuit with multiple outputs according to an embodiment of the invention. As shown in fig. 2, the reference voltage reference source includes current sources I1 and I2, first to sixth transistors NM1-NM6, a voltage adjustment element, an output of current source I1 is connected to a drain of NM1, an output of current source I2 is connected to a drain of NM2, a gate of NM1 is connected to a gate of NM2, a drain of NM1 is further connected to a gate of NM1 and provides a first reference voltage output VREF 1; the source of NM1 is connected to the drain of NM3, the drain of NM3 is connected to the gate thereof, the source of NM3 is connected to the drain of NM4, the drain of NM4 is connected to the gate thereof, and the source of NM4 is grounded; the source of NM2 is connected to the drain of NM5 through a voltage adjusting element, the drain of NM5 is connected to its gate and provides a second reference voltage output VREF2, the source of NM5 is connected to the drain of NM6, the drain of NM6 is connected to its gate, and the source of NM6 is grounded.

Wherein, the voltage adjusting element is an adjusting resistor; the first reference voltage is greater than a second reference voltage; the currents I1 and I2 of the left branch and the right branch are the same, and can be realized by a current mirror.

Further, the voltage adjustment element may be a series combination of a resistor and a diode, the diode being connected between NM2 and NM5 in a forward direction, for example: the anode of the diode is connected with the source of NM2, and the cathode of the diode is connected with the drain of NM5 through a resistor, or the source of NM2 is connected with the anode of the diode through a resistor, and the cathode of the diode is connected with the drain of NM 5. The arrangement of the diode can avoid the influence of a module driven by the second reference voltage source on the first reference voltage, improve the isolation between the reference voltages and further improve the reliability of the system.

In addition, the transistors NM1-NM6 may all employ NMOS transistors, and NM1-NM6 also have grounded body electrodes to further reduce noise of the circuit.

Illustratively, the first reference voltage is 1.8V and the second reference voltage is 1.2V.

The working principle of the invention is illustrated as follows: the NMOS transistors NM1-NM6 operate in the sub-threshold operating region,

I＝u_n*(W/L)C_d*V_T ²e(Vgs-Vth)/(nV_T)

then there are:

in the above formula, Un is the electric mobility, W and L are the gate width and the gate length of the transistor, Cd is the capacitance constant, VT ═ kT/q, T is the absolute temperature, Vgs is the overdrive voltage of the transistor, Vth is the threshold voltage of the transistor, and n is the sub-threshold constant.

Since NM1 and NM2 are identical in size, it is known that NM1 and NM2 have the same source voltage, and the current flowing through the adjustment resistor R can be derived from the above equation as follows:

I＝nV_T*ln(S₂S₅S₆/S₁S₃S₄)/R

in the above formula, S represents the gate width-length ratio W/L of the corresponding transistor, and R is the resistance value of the adjusting resistor.

Thus, an expression of the second reference voltage 1.2V can be obtained as follows:

V_{REF_1P2}＝2V_th+nV_T*ln[I/(u₀T^-1.5*S₅S₆*C_d*V_T ²)]

in the above equation, Vth is a term of negative temperature coefficient, which is about-1.5 degrees per degree Celsius; in the second term, VT ═ kT/q is proportional to absolute temperature T, and the following logarithmic term ln (T) is a weakly dependent expression of temperature, which can be considered approximately constant, so that the second term is a positive temperature coefficient term, which can be cancelled out by selecting appropriate NM5 and NM6 sizes, resulting in a temperature independent output voltage.

The expression of the first reference voltage 1.8V is as follows:

V_{REF_1P8}＝V_{REF_1P2}+IR+V_th+nV_T*ln[I/(u₀T^-1.5*S₂*C_d*V_T ²)]

where the first term is a constant voltage, the second term is a positive temperature coefficient term, the third term is a negative temperature coefficient term, and the last term is a positive temperature coefficient term, a temperature independent output voltage can be obtained by selecting appropriate dimensions of the transistors NMl and NM 2.

The reference voltage reference source shown in fig. 2 is simulated by using the simulation platform to obtain the output simulation result shown in fig. 3, and it can be seen that the 1.2V and 1.8V outputs obtained by proper design have small variation amplitude with temperature variation, and can meet stable operation.

The reference voltage circuit of the invention adopts a single reference voltage reference source, can provide two different output reference voltages at the same time through the transistor working at the sub-threshold, the output 1.2V and 1.8V of the reference voltage circuit basically do not change along with the fluctuation of temperature and power supply voltage, and the constant output is kept; therefore, the power supply reference source provided by the invention can effectively reduce the extra area and power consumption brought by the multi-path reference voltage reference source. The invention has simple structure, only one regulating resistor and the rest of NMOS transistors which can work in an extremely low current working state, has small process variation and extremely low required working current, and is very suitable for a reference voltage reference source of an SoC chip in wearable equipment.

Although the embodiments of the present invention have been described above, the above description is only for the convenience of understanding the present invention, and is not intended to limit the present invention. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the scope of the present invention should be determined by the following claims.

Claims

1. A multiplexed output reference voltage reference source, comprising: the reference voltage reference source includes a first current source (I1) and a second current source (I2), first to sixth transistors (NM1-NM6), a voltage adjustment element; wherein,

the output end of the second transistor is connected with the input end of a fifth transistor through a voltage adjusting element, the input end of the fifth transistor is connected with the control end of the fifth transistor and provides a second reference voltage output, the output end of the fifth transistor is connected with the input end of a sixth transistor, the input end of the sixth transistor is connected with the control end of the sixth transistor, and the output end of the sixth transistor is grounded; the first to sixth transistors are all operated in a subthreshold operation region.

2. The reference voltage reference source of claim 1, wherein the first current source and the second current source have equal currents.

3. The reference voltage reference source of claim 1, wherein the first and second current sources are implemented using current mirrors.

4. The reference voltage reference source of claim 1, wherein the voltage adjustment element is a tuning resistor.

5. The reference voltage reference source of claim 1 wherein the voltage adjustment element is a series combination of a resistor and a diode, the diode being connected in a forward direction between the output terminal of the second transistor and the input terminal of the fifth transistor.

6. The reference voltage reference source according to any one of claims 1 to 5, wherein the first to sixth transistors employ NMOS transistors.

7. The reference voltage reference source of claim 6 wherein the NMOS transistor further has a body connected to ground to further reduce circuit noise.

8. The reference voltage reference source according to any one of claims 1-5, wherein the first reference voltage is 1.8V and the second reference voltage is 1.2V.