WO2003093917A1

WO2003093917A1 - Circuit arrangement for providing a reference signal

Info

Publication number: WO2003093917A1
Application number: PCT/DE2003/001393
Authority: WO
Inventors: Martin Bosch; Johann Traub
Original assignee: Infineon Technologies Ag
Priority date: 2002-04-30
Filing date: 2003-04-30
Publication date: 2003-11-13
Also published as: DE10219347A1

Abstract

The invention relates to a circuit arrangement for providing a reference signal and comprising a diode (5) that serves as a reference element. The electrical reference quantity thereof is, however, firstly calibrated to a band gap reference (16) by means of a control loop (31, 14, 16) during a calibrating phase. The amplification of an amplifier (31) is set. Said amplifier comprises a network of resistors (8) containing a multitude of resistors (12) that can be switched on and off independent of one another.

Description

description

Circuit arrangement for providing a reference signal

The present invention relates to a circuit arrangement for providing a reference signal.

Reference signals in the form of a voltage reference or current reference are required for a large number of functional units in circuit technology, in particular for integrated circuits, for example for modulators, voltage-controlled oscillators, low-noise amplifiers, voltage regulators, amplifiers, etc. This serves the goal of setting certain electrical quantities to a desired level.

The electrical properties of the circuit that provides reference signals of this type must be taken into account, since their properties are included in the properties of the supplied circuits, namely the accuracy of the voltage or current provided, noise properties,

Own power consumption, temperature response and so on.

A very low power consumption of such viewing arrangements and particularly low noise are particularly desired for mobile radio applications. However, these are usually two conflicting requirements.

Bandgap circuits that are easy to integrate are normally used for the provision of reference signals, which is good, in particular, because of the exact voltage reference

Characterize temperature behavior and high stability. The disadvantage of such bandgap circuits, however, is their relatively high noise level. This can usually only be reduced with high power consumption.

Since, as explained, this is unsuitable for mobile radio, an integrated circuit is occasionally supplied there. voltage itself used as a reference signal. Of course, this has the disadvantage that both tolerances of the voltage supply, which are caused, for example, by the varying battery voltage, and interference signals in the frequency spectrum of the voltage supply are inevitably introduced into the supplied electrical circuit.

Another option for providing a reference voltage would be to use Zener diodes, the Zener voltage of which has a very high stability and accuracy. However, these have the disadvantage that they cannot be produced using practically all conventional semiconductor manufacturing processes.

The object of the present invention is to provide a circuit arrangement for providing a reference signal, which can be produced in integrated circuit technology, offers good noise properties with low power consumption and enables precise referencing with good temperature properties.

In the following, the terms electronic component and amplifier are used interchangeably. The terms controllable electronic property and controllable amplification are also used interchangeably.

According to the invention, the object is achieved by a circuit arrangement for providing a reference signal, comprising: a diode,

an electronic component which has a controllable electrical property which influences the dependence of the reference signal on an input signal of the electronic component, with an input to which the input signal can be fed and which is connected to the diode and has an output which the reference signal is provided is, and with a control input for setting the controllable electrical property, and - a control loop comprising a controller with a comparator, with an actual input, which is connected to the output of the electronic component, with a setpoint

Input which is connected to a reference source and an output which is connected to the control input of the electronic component operating as an actuator.

According to the present principle, the advantages of a

Band gap reference source on the one hand, such as the exact, temperature-stable provision of a reference voltage, and on the other hand a diode, which has an excellent noise behavior when flowing through, combined with one another. According to the present principle, this can be achieved by first, for example, calibrating the circuit arrangement by means of the reference source and the control circuit, which then has the effect that, in a subsequent referencing or normal operation, the diode has an exact, temperature-stable characteristic via the electronic component with adjustable properties and low-noise reference signal, which can be present both as a current signal or as a voltage signal.

Instead of a bandgap circle, other reference sources can also be provided. Combinations of several reference sources are also possible. Any dependencies on circuit parameters, such as, for example, on the temperature or the supply voltage, can thus be derived in order for a circuit supplied with the regulated voltage

To achieve advantages, such as temperature compensation of a voltage controlled oscillator.

The actual input can also be indirectly connected to the output of the electronic component, for example to the output of a circuit supplied by the reference signal. In this case the actual input is not the reference signal itself, but a signal derived from the reference signal.

The diode is preferably designed in bipolar circuit technology. Such bipolar diodes are in bipolar, in

BiCMOS as well as parasitic in pure CMOS (Complementary Metal Oxide Semiconductor) manufacturing processes are available and can therefore be easily manufactured in integrated circuit technology. The voltage reference of the diode, which can be calibrated with the reference source according to the principle presented, is preferably the base-emitter voltage of the diode designed as a correspondingly connected transistor, or generally the forward voltage, forward voltage or diode voltage of the diode.

Instead of a single diode, a series connection of several diodes or a parallel connection of several diodes can also be provided.

The calibration of the diode using the reference source and the

The controller and the adjustable electronic component primarily serve to compensate for any temperature dependencies that may exist and any manufacturing tolerances that may be present, which can be in the order of + -30 millivolts for diodes.

During an adjustment or calibration phase, the voltage derived from the diode is preferably converted by means of the electronic component into a tunable current, which is brought to a value by means of the control circuit, which is converted into a voltage and corresponds to the signal provided by the reference source.

The current provided by the electronic component can, if the reference signal is to be present as a reference voltage, for example via a resistor or by means of a combination of resistors and bipolar diodes. be transferred to the reference voltage. The electronic component is preferably designed as a resistance network with an adjustable resistance value, the resistance network comprising a plurality of resistors which can be switched on and off independently of one another.

Sections of conductor tracks can preferably be provided as resistors in order to achieve specific, desired temperature properties.

The controller preferably has an activation input for switching between a setting operating mode, which represents a calibration operation, and a normal operating mode, during which a calibrated reference signal is provided by means of the diode.

The reference source is likewise preferably switched off as a function of a signal present at the activation input or derived therefrom after a calibration has been carried out. For this purpose, the reference source preferably has a control input which is coupled to the activation input or to an output of the controller. This has the advantage that the relatively high noise components of the reference source, in particular if it is designed as a bandgap circuit, cannot act in normal operation in the reference signal provided by the circuit arrangement and the reference signal provided is therefore particularly low-noise.

The controller is preferably designed as a digital controller in such a way that the control input of the electronic component is designed to supply a digitally coded control signal which is provided by the comparator, which also works digitally. The controller can advantageously work with a digital approximation method, for example in accordance with the successive approximation, and can be designed accordingly. The circuit arrangement described is particularly suitable for providing a reference signal for the voltage supply of voltage-controlled oscillators, voltage-controlled oscillators, VCO, since any noise from the reference source that is present would have a particularly disadvantageous effect on the phase noise of the oscillator. Furthermore, the circuit described is particularly well suited for use in mobile radio because of the low power requirement.

Further details and advantageous embodiments of the present principle are the subject of the dependent claims.

The invention is explained in more detail below using several exemplary embodiments with reference to the drawings.

Show it:

FIG. 1 shows a first exemplary embodiment of a circuit arrangement according to the invention using a simplified circuit diagram of a reference voltage source,

Figure 2 shows a second embodiment of the circuit arrangement according to the invention using a simplified

Circuit diagram of a reference current source,

FIG. 3 shows an exemplary embodiment of a voltage regulator developed with reference to FIG. 1 on the basis of a simplified circuit diagram and

Figure 4 shows the principle of the circuit arrangement according to the invention using an exemplary, highly simplified block diagram.

FIG. 1 shows a circuit arrangement for providing a reference signal which is present as a reference voltage and which ches can be tapped at an output 1 of the circuit arrangement. A diode 5, which functions as a reference element, is connected to the output 1 via a current mirror 2, comprising a first transistor 3 connected as a diode and a further transistor 4. The diode 5 is designed as an NPN bipolar transistor, the base of which is short-circuited with its collector connection and connected to a supply potential connection 6. The diode 5 is arranged in a first current path which, in addition to the diode 5, comprises the current mirror transistor 3 which is connected by its emitter connection to the emitter connection of the diode 5, and a resistor 7 which is connected to the collector connection of the current mirror transistor 3 connected. The current mirror transistor 3 is connected as a diode in that its base is connected to its collector terminal. The basic connection of the PNP

Current mirror transistor 3 is also connected to the base connection of the further transistor 4, which is likewise designed as a PNP transistor and which together forms the current mirror 2. This is arranged with its emitter-collector path in a second current path, which includes a control element 8 in a series circuit in addition to the transistor 4, as well as a resistor 9 and a further diode 10. The control element 8 is on the one hand with the supply potential connection 6 and on the other hand with connected to the emitter terminal of transistor 4. The collector connection of transistor 4 is connected to output 1 and resistor 9, which in turn is connected via diode 10 to a reference potential connection 11. The resistor 7 of the first current path is also connected to the reference potential connection 11. The actuator 8 is designed as a resistance network with an adjustable resistance value and comprises a large number of resistors 12 which can be switched on and off independently of one another. The resistors 12 are each arranged in a series circuit comprising a switching transistor 13 and the resistor 12, the series circuits 12 , 13 are in turn connected in parallel. With the exception of one that is always on, the switching transistors 13 each have a control input that is associated with a ordered output DO to D4 of a digital controller 14 is connected. The controller 14 is constructed in such a way that it can carry out an adjustment according to the successive approximation method, as will be explained in more detail later. The controller 14 also has an input which is connected to the output of a comparator 15. The comparator 15 is designed as a comparator and comprises a target input and an actual input. The actual input is connected to output 1 of the circuit arrangement. The setpoint input is connected to the output of a reference generator 16 which is designed as a bandgap circuit and which is connected to reference potential connection 11. The bandgap circuit 16 comprises a control input for switching it on and off, which is connected to a correspondingly designed output of the controller 14. Finally, the controller 14 comprises a control input which is coupled to an activation input 17 of the circuit arrangement.

Depending on a signal present at the activation input 17, the circuit arrangement according to FIG. 1 can operate in two operating modes, namely a calibration mode and a normal mode. In the calibration mode, the reference source 16 provides a reference voltage which is compared with the reference voltage provided at the output 1 of the circuit. The result of this comparison is fed to the controller 14, which, depending on this, influences the switches 13 until the voltage value of the controller at the output 1 comes as close as possible to that of the bandgap circuit 16 using the method of successive approximation. The reference voltage value at output 1 is set as a function of the base-emitter voltage of diode 5, which works as a reference diode, and as a function of the settings on resistor network 8. A current flows through the resistor 7 and the diode 5, which defines the base-emitter voltage of the diode 5. This voltage is passed on via the current mirror 2 to the resistance bank of the setting device 8. If the calibration operation switched off, a voltage value dependent on the base-emitter voltage of the reference diode 5 and the calibrated resistance setting device 8 is practically applied to the output 1.

Since the bandgap circuit can be switched off in normal operation by means of the control signal which drives the reference source 16, good noise characteristics of the reference signal at output 1 can be expected in normal operation. In addition, the bipolar diode 5 has a very low self-consumption. The Bandga source 16 offers high accuracy and good temperature behavior, so that the present principle combines all the advantages mentioned. The circuit according to FIG. 1 is therefore particularly suitable for use as a voltage regulator for extremely low-noise requirements such as

For example, the voltage supply of voltage-controlled oscillators, whose phase noise is correspondingly low, is suitable. Since the output voltage at output 1 is provided as a voltage dropping via resistor 9 and further diode 10, a further improvement in the noise properties can be achieved with the further diode 10 connected in series.

While conventional circuits with low-noise bandgap circuits with an output voltage of 2.3 volts one

23 to 28 nV / NHz, a noise voltage of less than 8 nV / Hz can be achieved with a comparable bias current.

Alternatively, MOS transistors can be provided as resistors, which can be controlled directly with the digital control lines of the outputs DO to D4.

FIG. 2 shows an alternative embodiment of the circuit arrangement for providing a reference signal, which is designed in contrast to the circuit of FIG. 1 to provide a reference current instead of a reference voltage at output 1 of the circuit.

Apart from the second current branch 8, 4, 9, 10 of the circuit arrangement from FIG. 1, the circuit diagram of FIG. 2 does not differ in structure and mode of operation from that of FIG. 1 and should not be repeated again so far. In the second current branch 2, however, no series circuit comprising a resistor 9 and a diode 10 is connected between the collector terminal of the current mirror transistor 4, whose emitter terminal is still connected to the actuator 8, but a series circuit comprising a switch 18 and, depending on the switch position , The resistor 9, which is connected to the reference potential terminal 11. The switch 18 is on the one hand firmly connected to the collector terminal of the transistor 4. On the other hand, depending on the switch position, the switch 18 is either connected to a connection of the resistor 9 and to the actual input of the comparator 15 and in a second switch position to the output 1 of the controller arrangement. The control input of the switch 18, like the control input of the reference source 16, is coupled to the control output of the controller 14.

While in the setting mode, the current provided as a function of the diode 5 and its base-emitter voltage is converted into a voltage and brought to a corresponding value by the comparator 15 and the bandgap reference source, in the normal mode that of the diode 5 and the already calibrated setting device 8 as a function of the reference current provided directly on the

Output 1 of the circuit can be given.

The advantages with regard to noise properties, own power consumption, accuracy, stability and temperature response of the reference circuit according to FIG. 2 correspond to those of the reference circuit from FIG. 1. If the switch 18 is to be dispensed with, a further current source can also be provided as an alternative to the switch 18, in which case one of the current sources controls the comparator after conversion of the current into a voltage and another current source supplies the output 1 of the circuit.

Figure 3 shows a development of the voltage regulator of Figure 1, designed as an extremely low-noise low-drop voltage regulator. Only the deviations in FIG. 3 from FIG. 1 are to be described here. As in FIG. 1, a controller 14 is provided in the present case, which operates as a function of an activation signal at the activation input 17. According to FIG. 3, an actuator 19 designed as a programmable voltage divider is connected to several outputs for providing a digitally coded control signal from the controller 14. The programmable voltage divider 19 has a tap point which is connected to an actual input of a further comparator 20. The setpoint input of the further comparator 20 is connected to a circuit node between a current source 21, which is additionally connected to the supply potential connection 6 and the reference diode 5, which is connected on the emitter side to the reference potential connection 11. The output of the further comparator 20 is connected to a base connection of a PNP transistor 25, the collector connection of which is connected on the one hand to the programmable voltage divider 19 and on the other hand to the output 1 of the circuit and whose emitter connection is connected to the supply potential connection 6. Instead of the PNP transistor 25, a PMOS transistor can also be provided.

Comparator 15 is still provided, the nominal input of which is connected to reference generator 16 and the actual input of which is connected to output 1 by means of a voltage divider 22, 23 comprising two resistors. The

The output of the comparator 15 is connected to a control input of the controller 14 as in FIG. 1. The mode of operation of the low-noise voltage regulator according to FIG. 3 is illustrated below using a numerical example. The bandgap reference source 16 typically provides a voltage of 1.2 volts. So that a desired reference voltage of 2.4 volts is available at output 1, the voltage divider 22, 23 is designed with two resistors 22, 23 of the same size.

If the actual voltage value at output 1 deviates from the target value of 2.4 volts, then programmable voltage divider 19 is detuned by means of controller 14 until the target voltage of 2.4 volts is just being made available at the output. If one assumes that the reference diode 5 has a base-emitter voltage of approximately 0.8 volts, the divider ratio on the programmable voltage divider 19 will be adjusted according to the successive approximation method so that the resistance value resulting from parallel connection in adjusts the lower part of the voltage divider in total to half the value of the resistor 24 in the programmable voltage divider, such that a voltage of 1.6 volts drops across the resistor 24 and a voltage of 0.8 volts drops across the resistor network.

FIG. 3 accordingly combines the advantages of voltage regulation mentioned in FIG. 1 according to the principle presented with the advantages of a low-drop voltage regulator.

Figure 4 finally shows a highly simplified block diagram of the principle of the invention. A series circuit comprising a current source 30 and the reference diode 5 is connected between a supply connection 6 and a reference potential connection 11. The voltage drop across the diode 5 is fed to a digitally controllable amplifier 31 at its input, for this purpose the input is connected to the anode of the diode 5. The output of the variable amplifier is with output 1 of the circuit arrangement connected, at which the reference signal is present as a voltage reference or current reference. The variable amplifier 31 has a multiplicity of digital control inputs which are connected to the output of a digital controller 14. The digital controller 14 has an actual input which is connected to the output 1 of the circuit and a target input which is connected to a reference source 16. For example, amplifier 31 is designed with a programmable gain factor.

In a calibration operation, a signal derived from the voltage drop across the diode 5 is brought to the value of a reference signal provided by a reference source 16. For this purpose, the amplification ratio of the amplifier 31 is suitably programmed by means of the controller 14. This is done in a digital control, for example by successive approximation in several successive adjustment steps. In a subsequent normal operation, the reference source 16 can be switched off. Then the reference voltage drop across the diode 5 is in the

Amplifier 31 prepared in accordance with the programming and supplied to output 1 as a calibrated reference signal.

The advantages of the present principle can also be easily recognized from the block diagram of FIG. 4, namely

Combination of the extremely good noise properties and the low internal power consumption of the diode 5 combined with the high accuracy and the good temperature response of the reference source 15. LIST OF REFERENCE NUMBERS

1 exit

2 current mirror 3 transistor

4 transistor

5 diode

6 supply potential connection

7 resistor 8 actuator

9 resistance

10 diode

11 Reference potential connection

12 resistor 13 switch

14 controllers

15 comparators

16 Reference source

17 Activation input 18 switch

19 voltage dividers, programmable

20 comparators

21 power source

22 resistance 23 resistance

24 resistance

25 transistor

30 power source

31 programmable amplifiers

Claims

claims

1. Circuit arrangement for providing a reference signal, comprising - a diode (5),

- An amplifier (31) which has a controllable gain which influences the dependence of the reference signal on an input signal of the amplifier (31), with an input to which the input signal can be fed and which is connected to the diode (5) with an output (1) at which the reference signal is provided and with a control input for setting the controllable gain, and

- A control circuit comprising a controller (14) with a comparator, with an actual input, which is connected to the output of the amplifier (31), with a desired input, which is connected to a reference source (16), and with an output which is connected to the control input of the amplifier (31) operating as an actuator.

2. Circuit arrangement according to claim 1, d a d u r c h g e k e n n z e i c h n e t that the diode (5) is formed in bipolar circuit technology, the base-emitter voltage represents the input signal to the amplifier (31) can be supplied.

3. Circuit arrangement according to claim 1 or 2, so that the amplifier (31) comprises a resistor network (8) with an adjustable resistance value, with a plurality of resistors (12) which can be switched on and off independently of one another.

4. Circuit arrangement according to one of claims 1 to 3, characterized in that the controller (14) comprises an activation input (17) for switching between a setting mode of the circuit arrangement for calibrating the amplifier (8, 31) and one Normal operating mode for providing a calibrated reference signal using the diode (5).

5. Circuit arrangement according to claim 4, d a d u r c h g e k e n n z e i c h n e t that the reference source (16) is designed to be switched off in dependence on the activation signal for its switching off during the normal operating mode.

6. Circuit arrangement according to one of claims 1 to 5, that the reference source (16) is designed as a bandgap generator which provides a bandgap voltage at its output.

7. Circuit arrangement according to one of claims 1 to 6, that the controller (14) is designed to adjust the controllable gain of the amplifier (8, 31) in a digital approximation method.

8. Circuit arrangement according to one of claims 1 to 7, so that the amplifier (31) working as an actuator is designed as a voltage divider with a programmable divider ratio (19).