Patent Grant
8427129
This invention relates to voltage reference generation circuits.
Electronic devices and systems are pervasive in modern society. The key components of many modern electronic systems and devices include semiconductor chips. The semiconductor chips may be used for a variety of purposes and include such things as control circuitry and memory devices.
Many of the semiconductor chips that are used for various applications consist of a semiconductor die that is housed in a package. The semiconductor die contained in a package is electrically connected to the input and output leads of the package. The package is in turn electrically coupled to various other circuitry in the electronic device. Among the inputs that are supplied to the chip from the other circuitry to which it is coupled is a power supply input.
The power that is supplied to the chip by the other circuitry is often not adequate for the chip's requirements. This may be the case for a variety of reasons. For example, the power supply may have too much noise for the chip to function at its optimum level.
The high current drive bandgap based voltage regulator includes a high current drive output transistor having a transistor input terminal and a transistor output terminal. A feedback network is coupled between the output of the transistor and the input terminal of the transistor. The high current drive bandgap based voltage regulator also includes an operational amplifier in the feedback loop. The operational amplifier has at least two operational amplifier input terminals and an operational amplifier output terminal. The operational amplifier output terminal is coupled to the transistor input terminal and the operational amplifier input terminals are coupled to the transistor output terminal. The output of the voltage reference generation circuit is coupled to the output of the high current drive transistor.
In one aspect the embodiments provide a high current drive bandgap based voltage regulator for providing a reference voltage at a designed output voltage value.
The high current drive bandgap based voltage regulator includes a high current drive output transistor having a transistor input terminal and a transistor output terminal. A feedback network is coupled between the output of the transistor and the input terminal of the transistor. The high current drive bandgap based voltage regulator also includes an operational amplifier in the feedback loop. The operational amplifier has at least two operational amplifier input terminals and an operational amplifier output terminal. The operational amplifier output terminal is coupled to the transistor input terminal and the operational input terminals is coupled to the transistor output terminal. The output of the voltage reference generation circuit is coupled to the output of the high current drive transistor.
The high current drive bandgap based voltage regulator is operable to provide a current of at least 100 μA to the output terminal while maintaining the output voltage at the output terminal at a value substantially equal to the designed output voltage value.
Several examples of the present invention will now be described in detail with reference to the drawings, in which:
Reference is first made to
In this embodiment, resistor 112 may be used together with resistor 114 to form a voltage divider. The feedback loop may be connected to voltage divider internal node 126 within the voltage divider. For example, resistor 112 is coupled between high current drive bandgap based voltage regulator output terminal 122 and resistor 114. Resistor 114 is coupled between resistor 112 and a negative polarity terminal, which can be, for example, a ground terminal or a negative voltage supply terminal. In various embodiments, resistors 112 and 114 can be selected to have particular values so that high current drive bandgap based voltage regulator 100 provides a reference voltage at particular value, which may be referred to as the designed output voltage value. Thus, the designed voltage value can depend on various parameters including the values of resistors 112 and 114 and the bandgap voltage of the substrate used to implement the high current drive bandgap based voltage regulator 100. For example, in some embodiments, silicon may be used to implement the substrate and therefore the bandgap voltage of silicon would be a parameter that affects the designed voltage value. In various other embodiments, any appropriate substrate may be used.
The designed output voltage can be expressed as
where Vout is the designed output voltage, Vbandgap is the bandgap voltage of the substrate (e.g. for embodiments that utilize silicon as a substrate, the bandgap voltage is the bandgap voltage of silicon), R112 is the resistance value of resistor 112, and R114 is the resistance value of resistor 114.
In various other embodiments, resistors 112 and 114 are not utilized. In such embodiments, both the output terminal 122 and the feedback network 120 are coupled to the source terminal of transistor 104. In such embodiments, the designed voltage value can be different than when a voltage divider is used. More specifically, Vout=Vbandgap, where Vout is the designed output voltage and Vbandgap is the bandgap voltage of the substrate (e.g. for embodiments that utilize silicon as a substrate, the bandgap voltage is the bandgap voltage of silicon).
High current drive output transistor 104 is a transistor that is capable of sourcing a large current. In some embodiments transistor 104 is an NMOS (n-channel metal oxide semiconductor) transistor. In certain applications, the use of an NMOS transistor may provide better power supply rejection than would the use of an equivalent PMOS transistor in an analogous design. Power supply rejection is a measure of a device's ability to tolerate changes in the power supply. Given that in many instances, the use of a high current drive bandgap based voltage regulator may be prompted by the need for power supply rejection, an NMOS device may be more appropriate in certain circumstances.
Known voltage reference generators such as that illustrated in
Reference is now made to
In general, the width W of the transistor 400 is made sufficiently wide such that an appropriate amount of current can be supplied to the current consuming circuit. If the output transistor is not sufficiently wide, then the high current drive bandgap based voltage regulator may not be able to supply sufficient current to the current consuming circuit and the voltage may not be maintained at an appropriate level. The manner in which this is accomplished is discussed in further detail below.
The width of a transistor can be expressed as the total width (Wt) or as the width of a single finger (Wfinger) and a variable (e.g. M) to indicate the number of fingers present in the transistor. As used herein W will be used to refer to the total width of a transistor (i.e. W=Wt).
Various embodiments of the high current drive bandgap based voltage regulator 100 made in accordance with Applicant's teachings may be used for a wide variety of applications. Examples of possible applications in which embodiments of the regulators discussed herein may be used include, but are not limited to, low-noise amplifiers, digital to analog converters (DACs), analog to digital converters (ADCs), phased lock loops (PLLs), filters, and a variety of Radio Frequency (RF) circuitry such as Mixers, LNA, and RF filters.
In each of these applications, the design of the specific embodiments of the high current drive bandgap based voltage regulator 100 may be altered in order to better suit the needs of the particular application. Specifically, each of these different embodiments of high current drive bandgap based voltage regulator 100 may be optimized in various manners. For example, these optimizations may be accomplished by altering the width W and length L of output transistor 104 as well as the loop gain of feedback network 120 and bandwidth of operational amplifier 102 and output transistor 104. This may effectively trade off several characteristics including, but not limited to, device noise, supply noise rejection, current sourcing ability, and regulation.
Various embodiments of the high current drive bandgap based voltage regulator 100 can output various values of currents. For example, in some embodiments high current drive bandgap based voltage regulator 100 can output a current of at least 100 μA. In some other embodiments, high current drive bandgap based voltage regulator 100 can output a current of at least 1 mA. In some other embodiments, high current drive bandgap based voltage regulator 100 can output a current of at least 10 mA.
In one embodiment, 0.35 μm CMOS technology is utilized to implement output transistor 104 of high current drive bandgap based voltage regulator 100. The output transistor 104 has the following parameter values: L=0.38 μm, Wfinger=5 μm, M=70, and therefore, W=Wfinger×M=(5 μm)×70=350 μm. The use of these values allows the output transistor to drive a current of up to 10 mA. In other implementations, other technology may be used and the parameter values can be adjusted accordingly.
Various embodiments of the high current drive bandgap based voltage regulator 100 may be utilized in a variety of applications. The particular embodiment utilized depends on the particular requirements of the applications in which it is to be used. The above discussion was intended to be an example only. There are a wide variety of applications in which high current drive bandgap based voltage regulator 100 can be used of which only a few have been discussed for illustrative purposes.
The high current drive bandgap based voltage regulator according to Applicant's teachings may be implemented in a wide variety of embodiments. Reference is now made to
In embodiments based on this design, transistor 504 is a PMOS (p-channel metal oxide semiconductor) transistor. The use of a PMOS transistor can add more gain to the feedback loop than an equivalent NMOS transistor. This can negatively affect the stability of the overall regulator. However, depending on the process used to fabricate the semiconductor circuit, a PMOS transistor may generate less noise then an equivalent NMOS transistor.
In various embodiments, the high current drive bandgap based voltage regulator may be implemented using a biCMOS design. As is known to those skilled in the art, biCMOS designs allow for the combination of advantages of both CMOS and Bipolar transistors in a single circuit. For example, bipolar transistors generally have a greater current driving capability for a given area than do CMOS transistors. On the other hand, CMOS transistors generally have a higher input impedance than do bipolar transistors. The various embodiments illustrated in
In some embodiments the output transistor of the high current drive bandgap based voltage regulator is a bipolar transistor. This may provide for several advantages over using a CMOS output transistor. In particular, it may provide for a greater current driving capability for a given area as well as lower noise. In addition, the use of the bipolar transistor may allow for better regulation characteristics.
Reference is now made to
Operational amplifier 602, resistors 606, 608, 610, and 612 as well as diodes 616 and 618 comprise feedback network 620. One end of feedback network 620 is coupled to the inputs of operational amplifier 602 and the other end of the feedback network 620 is coupled to voltage divider internal node 626. The output of high current drive bandgap based voltage regulator 600 is taken at output terminal 622. Output terminal 622 can be coupled to a current consuming circuit 624.
In various embodiments, bipolar transistors can be used to implement the operational amplifier. This would allow for a lower noise operational amplifier. The decision to use bipolar transistors in the operational amplifier can be made regardless of the specific implementation used for the output transistor. In particular, the operational amplifiers of
The present invention has been described here by way of example only. Various modification and variations may be made to these example embodiments without departing from the spirit and scope of the invention, which is defined by the appended claims.
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