Isolation amplifier with reconfigurable filter

Abstract

Examples of circuitry and systems and methods provide a multi-way configurable amplifier (200) to support various applications. The multi-path configurable amplifier (200) may include a reconfigurable filter (204) comprising: a first input (216) and a second input (218) adapted to receive an input signal; a fully differential amplifier (FDA) (232); and a first reconfigurable resistance-capacitance (RC) network (234) and a second reconfigurable RC network (236). The FDA (232) has an inverted input, a normal input, an inverted output, and a normal output. The inverting input is coupled to the first input (216) and the non-inverting input is coupled to the second input (218). The first reconfigurable RC network (234) is coupled to the positive phase output, and the second reconfigurable RC network (236) is selectively coupleable to the negative phase output. The reconfigurable filter (204) can be configured to enable operation in any of a plurality of modes including a single-ended mode of operation and a differential mode of operation.

Description

Technical Field

[0001] The present specification generally relates to a reconfigurable filter to enable an isolation amplifier to operate in any of a plurality of modes, including a fully differential mode, a single-ended mode generating a single-ended output from a differential input, and a unipolar mode to support a plurality of different products, including direct interface with a single-input analog-to-digital converter (ADC). Background Art

[0002] An isolation amplifier has an output separated from the input circuitry of the amplifier by an isolation barrier that can withstand high voltages. The isolation barrier separates parts of the system that operate on different common-mode voltage levels and protects the low-voltage side from hazardous voltages and damage. The input of the isolation amplifier can be optimized for direct connection to a low-impedance shunt resistor or other low-impedance voltage source with low signal levels. Applications such as isolated voltage or current sensing in various environments including automotive require excellent DC accuracy and low-temperature drift.

[0003] Many isolation amplifiers used in such sensing applications provide a differential analog output between two output pins that can interface with a differential input ADC. However, in order to interface with a single-ended input ADC, such amplifiers require external circuitry to convert the amplifier output to a ground-referenced single-ended signal for input to the single-ended input ADC. However, this external circuitry requires additional space, increases complexity, and increases the cost of the overall product.

[0004] Another existing method of interfacing an isolation amplifier with a single-ended input ADC is to use two such ADCs, one coupled to one of the differential outputs of the amplifier and the other coupled to the other of the differential outputs of the amplifier. This approach has accuracy issues because the signal measured at each output pin of the amplifier with respect to ground is not an exact signal. Overhead is added in terms of space, complexity, and cost to accommodate two ADCs and address accuracy issues.

[0005] It is within this context that features and aspects of the present specification emerge. Summary of the invention

[0006] In an example, a reconfigurable filter includes: a first input and a second input adapted to receive an input signal; a fully differential amplifier (FDA); and a first reconfigurable resistor-capacitor (RC) network and a second reconfigurable RC network. The FDA has an inverting input, a non-inverting input, an inverting output, and a non-inverting output. The inverting input is coupled to the first input, and the non-inverting input is coupled to the second input. The first reconfigurable RC network is coupled to the non-inverting output, and the second reconfigurable RC network is selectively coupled to the inverting output. The reconfigurable filter can be configured to enable operation in any of a plurality of modes including a single-ended operation mode and a differential operation mode.

[0007] In an example, a system (e.g., which may be or include an isolation amplifier) ​​includes: a digital-to-analog converter (DAC); a multiple feedback (MFB) filter; and a plurality of terminals including an output terminal, a multi-function terminal, a voltage supply terminal, and a ground terminal. The DAC has a digital input, a DAC reference voltage input, a first output, and a second output. The first input and the second input of the MFB filter are coupled to the first output and the second output of the DAC, respectively. The MFB filter includes a fully differential amplifier (FDA) having an inverting input, a non-inverting input, an inverting output, and a non-inverting output. The inverting input is coupled to the first input, and the non-inverting input is coupled to the second input. The MFB filter can be configured to enable the amplifier of the system to operate in any one of a plurality of modes including a single-ended operation mode and a differential operation mode.

[0008] In an example, a method includes: controlling a first reconfigurable resistor-capacitor (RC) network of a filter of an amplifier to set the amplifier in a selected operating mode among a plurality of operating modes; controlling a second reconfigurable RC network of the filter to set the amplifier in the selected operating mode; selecting a source of a reference voltage input to a digital-to-analog converter (DAC) of the amplifier based on the selected operating mode; and generating an output signal by the amplifier according to the selected operating mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 Figure 2 is a diagram of an example isolation amplifier.

[0010] Figure 2 is a diagram of an example filter system including an example multi-way reconfigurable multiple feedback (MFB) filter to enable an isolation amplifier to operate in any of a plurality of modes.

[0011] Figure 3 is a diagram of another example filter system including an example multi-way reconfigurable MFB filter to enable an isolation amplifier to operate in any one of a plurality of modes.

[0012] Figure 4Ais a diagram of an example isolation amplifier system that includes circuitry to enable direct coupling to a single-ended input ADC.

[0013] Figure 4B is a diagram of another example isolation amplifier system that includes circuitry to enable direct coupling to a single-ended input ADC.

[0014] Figure 5 To set up the instance multi-way reconfigurable MFB filter in a specific configuration (e.g. Figure 2 or 3) to enable an associated isolation amplifier to operate in a specific mode. DETAILED DESCRIPTION

[0015] Specific examples are described in detail below with reference to the accompanying drawings. In the drawings, corresponding numerals and symbols generally refer to corresponding parts unless otherwise indicated. Objects depicted in the figures are not necessarily drawn to scale.

[0016] In an example arrangement, systems, circuits, and methods provide an isolation amplifier with a multi-way reconfigurable MFB filter to enable the isolation amplifier to operate in any of a plurality of modes, including a fully differential mode, a single-ended mode, and various unipolar modes, in which a single-ended ground referenced output signal is generated from an input signal, which may be a differential input signal. Circuitry is also provided to enable the single-ended output to be directly coupled to a single-ended input ADC and to scale the single-ended ground referenced output signal with a reference voltage that matches the full scale range of the ADC. The reference voltage may be provided through a dedicated or shared terminal (or pin). The arrangement advantageously supports a plurality of different products and applications.

[0017] Figure 1 1 is a diagram of an example isolation amplifier 100, which includes an input side circuit system 102 for processing a differential signal input at terminals INP and INN of the isolation amplifier 100. Its terminal VDD1 is suitable for coupling to a high-side voltage source referenced to GND1, which may be 3.3V or 5V. Terminal GND1 of the isolation amplifier 100 is suitable for coupling to a high-side ground. The isolation amplifier 100 further includes an output side circuit system 104 separated from the input side circuit system 102 by an isolation barrier 106. On the output side, terminal VDD2 is suitable for coupling to a low-side voltage source, which may be, for example, 3.3V or 5V. Terminal GND2 is suitable for coupling to a low-side ground. In the isolation amplifier 100, terminals OUT(P) and OUTN / V REFIN serves multiple purposes. When the isolation amplifier 100 is configured in differential mode, a differential output signal (OUTP-OUTN) is output at these terminals. When the isolation amplifier 100 is configured in single-ended mode or in any of the various unipolar modes, a single-ended output signal (OUT) is output at terminal OUT(P) referenced to GND2, while terminal OUTN / V REF IN is used as an external reference voltage supply (V REF IN) or midpoint referenced input. Therefore, OUTN / V REF The IN terminal may be considered a multi-function terminal. A multiple feedback (MFB) filter is provided as part of the output circuitry 104 to configure the isolation amplifier 100 in its various modes and to facilitate low pass filtering after D / A conversion.

[0018] Figure 2 FIG. 2 is a diagram of an example of such a multi-way reconfigurable MFB filter (or filter assembly) 204 within a filter system 200. The filter system 200 also includes a digital-to-analog converter (DAC) 202 that drives the filter assembly 204. The DAC 202 has a digital input 206 at which a bit stream (bs) is input and a DAC reference voltage input 208 at which a DAC reference voltage (V REF _DAC), the voltage signal can be obtained in different ways depending on the operating mode. The voltage signal is input to the DAC 202 through the buffer 210. The DAC 202 is configured to output a differential analog signal at a first output 212 and a second output 214, respectively. The bit stream (bs) can be the output of an analog-to-digital converter (ADC) (not shown) at the input side of the isolation amplifier 100.

[0019] The first output 212 and the second output 214 of the DAC 202 are coupled to the corresponding first input 216 and the second input 218 of the filter component 204. The first output 212 is coupled to the first input 216 via a first pair of resistors 222, and the second output 214 is coupled to the second input 218 via a second pair of resistors 224. Each of the first pair and the second pair of resistors may have a resistance that is a multiple of R, where R represents a unit value of resistance or other suitable resistance consistent with the teachings herein. A capacitor 226 may be coupled between a first node between the resistors of the first pair and a second node between the resistors of the second pair. In another example, the capacitor 226 may be omitted. Another capacitor 228 is coupled between the first input 216 and the second input 218 of the filter component 204. When used, the capacitor 226 may have a capacitance of nC, where n is a factor, and C represents a unit value of capacitance. The capacitor 228 may have a capacitance of mC, where m is another factor that may be different from the factor n. In some examples, the resistors in each of the first and second pairs directly coupled to the DAC 202 and the capacitor 226 can be separate from the filter component 204 .

[0020] The filter component 204 includes a fully differential amplifier (FDA) 232 that can be reconfigured to drive OUTP only as an operational amplifier (op amp), a first reconfigurable resistor-capacitor (RC) network 234, and a second reconfigurable RC network 236. FDA 232 has an inverting input (-) and a non-inverting input (+), as well as an inverting output (-) and a non-inverting output (+). FDA 232 can be configured via a switching mechanism so that its inverting output can be disabled (e.g., set to a high impedance state). This is illustrated by an external switch 238 coupled to the inverting output of FDA 232, but other techniques can be used to achieve the disablement. For example, one or more switches within FDA 232 can be used to disable (float, tri-state) OUTN without being connected in series with the output. RC network 234 is coupled between the non-inverting output and the inverting input of FDA 232. In the external switch example, the RC network 236 may be selectively coupled to the inverting output of the FDA 232 via the switch 238 , and also coupled to the non-inverting input of the FDA 232 .

[0021] The filter component 204 further includes a first integrator resistor 242 and a second integrator resistor 244, respectively. The first integrator resistor 242 is coupled between the first input 216 of the filter component 204 and the inverting input of the FDA 232, and the second integrator resistor 244 is coupled between the second input 218 of the filter component 204 and the non-inverting input of the FDA 232. The integration resistors 242 and 244 may also be referred to as input resistors due to being coupled to the inputs of the FDA 232.

[0022] The first RC network 234 includes a first variable resistance element 252 and a first variable capacitance element 254. The first variable resistance element 252 is coupled between the non-inverting output of the FDA 232 and the input 216 of the filter component 204, while the first variable capacitance element 254 is coupled between the non-inverting output of the FDA 232 and the inverting input thereof. The first variable resistance element 252 represents one or more resistors that can be configured to provide a specific resistance between the non-inverting output of the FDA 232 and the input 216 of the filter component 204. Similarly, the first variable capacitance element 254 represents one or more capacitors that can be configured to provide a specific capacitance between the non-inverting output and the inverting input of the FDA 232.

[0023] The second RC network 236 includes a second variable resistance element 256 and a second variable capacitance element 258, which have input terminals coupled to the input 218 of the filter component 204 and the non-inverting input of the FDA 232, respectively. In an example, the output terminals of the second variable resistance element 256 and the second variable capacitance element 258 can be selectively coupled to the inverting output of the FDA 232 via the switch 238. In another example, as described above, the inverting output of the FDA 232 can be activated (e.g., by an internal mechanism) to thereby activate the second RC network 236. As with the first variable resistance element 252 and the first variable capacitance element 254, the second variable resistance element 256 and the second variable capacitance element 258 represent one or more components, respectively. Therefore, one or more resistors can be used to configure the second variable resistance element 256 to provide a specific resistance in its electrical path, and one or more capacitors can be used to configure the second variable capacitance element 258 to provide a specific capacitance in its electrical path.

[0024] The filter component 204 also includes a variable resistor 262, which may be one or more resistors, coupled between the input 218 and the ground terminal (GND2). The terminal OUT(P) of the filter component 204 is coupled to the non-inverting output of the FDA 232. When the filter component 204 is configured in the differential mode, the terminal OUTN / V REF IN is used as an output terminal (OUTN), in which case switch 238 is closed (in the external switch example), thereby coupling this terminal to the inverting output of FDA 232. In single-ended mode, switch 238 (when used) is open, in which case OUTN / V REF IN is used as input terminal (V REF IN).

[0025] In addition to the switch 238 (or other mechanism for activating / deactivating the inverting output of the FDA 232), the first RC network 234 and the second RC network 236 may also be configured. Figure 3The reconfigurable MFB filter (or filter component) 304 in shows an example structure and control scheme for the RC networks 234 and 236 , which is shown in the context of the example filter system 300 .

[0026] In addition to illustrating example structures and operations of variable resistance elements 252 and 256 and variable capacitance elements 254 and 258, Figure 3 Additional components of filter assembly 304 are also shown that are also used to configure isolation amplifier 100. Components of filter assembly 304 that are identical or substantially similar to components of filter assembly 204 are identified with the same reference numerals as their respective counterparts of filter assembly 204.

[0027] In the example filter component 304, the variable resistance element 252 includes a resistor 302, which can be selectively coupled between the input 216 and the output terminal OUT(P) of the filter component 204 via a switch 305, which can be in the form of an n-channel metal oxide semiconductor (NMOS) field effect transistor (NMOS transistor). When the switch 305 is turned on (conductive), the resistor 302 is coupled between the input 216 and OUT(P); otherwise, the path of the resistor 302 and the switch 305 is disconnected. Figure 3 In the example of , the resistive element 252 further includes a pair of resistors 306 and 308, which can be configured for series operation or to use only resistor 308 in the event that resistor 306 is shorted. Therefore, the (NMOS transistor) switch 310 is coupled across the terminals of the resistor 306 to create a short circuit path when the switch 310 is turned on (conductive). Therefore, by using switches 305 and 310, a variety of different resistance values ​​can be set for the reconfigurable RC network 234 of which the variable resistive element 252 is a part. In the example, the resistance of resistor 302 is 3R, and when switch 310 is open, the resistance of each of resistors 306 and 308 is 1.5R, where the series equivalent is 2×1.5R.

[0028] Reconfigurable RC network 234 also includes variable capacitance element 254, which in example filter component 304 includes capacitors 312 and 314 and (NMOS transistor) switch 316. Depending on whether switch 316 is on or off, the capacitance between the OUT(P) terminal (also the non-inverting output terminal of FDA 232) and the inverting input terminal of FDA 232 can be the total capacitance (2C) of capacitors 312 and 314 coupled in parallel, or can be the capacitance (C) of capacitor 314.

[0029] The reconfigurable RC network 236 is similarly constructed using switch control of multiple resistors and capacitors. In the illustrated example, the variable resistive element 256 includes two resistors 322 and 324 and a (NMOS transistor) switch 326. As configured, the switch 326 can be used to set the resistance of the reconfigurable RC network 236 to the sum of the resistances of the resistors 322 and 324 (2×1.5R), or simply to the resistance of the resistor 324 (1.5R). In the example filter component 304, the variable capacitive element 258 of the reconfigurable RC network 236 includes two capacitors 332 and 334 and a (NMOS transistor) switch 336, which can be used to set the capacitance of the reconfigurable RC network 236 to one of two different capacitances, namely C or 2C.

[0030] In filter component 304, variable resistor 262 is implemented by a resistor and a switch coupled in series. In the illustrated example, the variable resistor can have a value of 3R or substantially infinity (∞), depending on whether the switch is closed or open.

[0031] The example filter component 304 further includes a V REF The switching circuit system includes a circuit system coupled to the terminal OUTN / V REF The switch circuitry further includes a resistor 346 coupled in parallel with a capacitor 348 between the first input of the multiplexer 344 and ground (GND2). REF ) 352 is coupled to a second input of multiplexer 344. The output of multiplexer 344 is coupled to the input of buffer 210, the output of which is coupled to DAC reference voltage input 208. Depending on the operating mode, multiplexer 344 selects V REF _DAC source.

[0032] In an example, to configure amplifier 100 in differential mode to generate a differential output signal in response to a differential input signal, switch 238 is closed and reconfigurable RC networks 234 and 236 are configured as follows. In reconfigurable RC network 234, switch 310 is closed, switch 305 is closed, and switch 316 is closed, thereby providing a resistance of 1.5R and a capacitance of 2C. In reconfigurable RC network 236, switch 326 is closed, and switch 336 is closed, thereby providing a resistance of 1.5R and a capacitance of 2C. In differential mode, the switch of variable resistor 262 is open, thereby providing infinite resistance. In addition, in differential mode, multiplexer 344 selects the input from voltage source 352 as V REF _DAC source.

[0033] The following table shows example configurations for differential input mode and other modes, each of which can be obtained by controlling the switches of filter component 304. In all modes except differential mode, switch 238 is open. For ratiometric mode, V REF _DAC through the amplifier 100 V REF IN terminal. In single-ended (SE) mode with ratiometric scaling (ratio), and in unipolar ratiometric mode, the voltage signal input to buffer 210 is V REF IN / 3, while in other modes (fixed gain), the voltage signal input to buffer 210 is V REF In unipolar 1.5V / V mode or unipolar 1V / V mode, the output swing can be offset by V REF IN or its fraction. Voltage V clip is the absolute clipping voltage on the high side (INN-INP), and V REF is the internal reference voltage.

[0034]

[0035] Figure 3 An example of how reconfigurable RC networks 234 and 236 may be structured is shown. Other arrangements consistent with the teachings herein are possible. For example, a second order MFB filter may be used, in which case capacitor 226 may be omitted. Each RC network may include any suitable combination of resistors coupled in parallel and / or series, and any suitable combination of capacitors coupled in parallel and / or series, and a control switch. Similarly, Figure 3 An example configuration of variable resistor 262 is shown; however, it may be configured in any suitable manner to obtain the desired resistance for a given mode of operation.

[0036] Figure 4A and 4B Different examples of larger systems (i.e., environments) 400 and 450 are shown, respectively, in which the isolation amplifier 100 is configured in single-ended mode to generate a single-ended ground referenced output signal at its output (OUT) in response to a differential input signal, the output being directly coupled to a single-ended input ADC 402, which may be part of a microcontroller unit (MCU). In the systems 400 and 450, the multi-function terminal (OUTN / V REF IN) is configured as the reference input terminal (V REF IN) to receive the reference voltage (V REF ).

[0037] Both systems 400 and 450 include input circuitry 404. Figure 4A and4B In the example of FIG. 4 , the input circuit system 404 includes a low impedance shunt resistor (R SHUNT ) to generate an input signal transmitted to the input terminals INP and INN of the isolation amplifier 100. SHUNT One end of is coupled to the input side ground terminal (GND1) of the isolation amplifier 100. Depending on the application, the input circuit system 404 may be different from the input circuit system shown. In the illustrated example, the differential input signal is approximately 640 mV peak-to-peak (pp).

[0038] In both systems 400 and 450, the input side voltage supply terminal (VDD1) of the isolation amplifier 100 may be coupled to a voltage source (not shown). In addition, in both systems 400 and 450, the output side voltage supply terminal (VDD2) of the isolation amplifier 100 is coupled to the voltage supply terminal (VDDA) of the MCU, and these two terminals are commonly coupled to a voltage source, which may be in the range of approximately 2.7V to 5.5V, such as 3.3V, and may be different from the voltage source on the input side. The output side ground terminal (GND2) and the ground terminal of the MCU are both coupled to a common ground. Figure 4A and 4B The voltages indicated in are examples.

[0039] exist Figure 4A In the system 400, V REF The IN terminal is coupled to both the VREFHI terminal and the VDDA terminal of the MCU. Figure 4B In the system 450, V REF IN terminal is coupled only to VREFHI terminal, and voltage source 452 is coupled to V REF The voltage source 452 is configured to generate an external reference voltage (V REF _EXT), the external reference voltage is connected to the V REF The IN terminal is supplied to the isolation amplifier and to the MCU via the VREFHI terminal of the MCU. In the example, V REF _EXT can range between about 2.7V and a voltage of VDD2; other ranges are possible. In an example, V REF _EXT is less than the voltage supplied to VDD2 and VDDA.

[0040] The single-ended ground referenced output signals generated by each of systems 400 and 450 are scaled with the differential input signals (bipolar inputs). Figure 4A and 4B In the example of FIG. 1 , the output voltage (V(OUT, GND2)) of the isolation amplifier 100 is substantially V REFIN / 2 is centered. At zero input, the amplifier 100 outputs approximately V REF IN / 2; in response to a positive input signal, the output of amplifier 100 is approximately V REF IN / 2 and V REF IN; and in response to a negative input signal, the output of amplifier 100 is approximately V REF IN / 2 and ground (zero). In addition, in the example systems 400 and 450, Where Vin is V INP -V INN , and A represents a fixed gain value; in this example, A = 1 / V clip Other input / output signal combinations are possible. For example, in the case of unipolar fixed gain mode, the output voltage is driven as follows. At zero input, the amplifier 100 output closely follows V REF IN or a fraction thereof, and in response to a positive input signal, the amplifier 100 is at zero and A*V REF Output between, where in the examples in the above table, A can be 1.5 or 3.

[0041] Figure 5 Flowchart of an example method 500 of operating an isolation amplifier (eg, isolation amplifier 100 ) having a reconfigurable MFB filter (eg, MFB filters 204 and / or 304 ).

[0042] In operation 502, a first reconfigurable resistor-capacitor (RC) network of a multiple feedback filter of an amplifier (e.g., an isolation amplifier) ​​is controlled to set the amplifier in a selected operating mode among a plurality of operating modes. In operation 504, a second reconfigurable RC network of the multiple feedback filter is controlled to set the amplifier in the selected operating mode. Control or configuration of the first reconfigurable RC network and the second reconfigurable RC network may be performed via a switch (e.g., an NMOS transistor), as described above. In operation 506, a source of a reference voltage input to a digital-to-analog converter (DAC) of the amplifier is selected based on the selected operating mode. With the amplifier so configured, in operation 508, an output signal is generated according to the selected operating mode.

[0043] Figure 5 Describes one possible set and order of operations. Not all operations must be performed in the order described. Some operations may be combined into a single operation. Additional operations and / or alternative operations may be performed.

[0044] Examples of circuit systems, systems, and methods provide a multi-channel configurable isolation amplifier that supports unipolar sensing applications and bipolar sensing applications. By adopting a multi-channel reconfigurable MFB filter, the amplifier can utilize the full dynamic range of the downstream ADC and thus maximize the measurement resolution. No external circuit system is required to generate a single-ended output signal, thereby reducing board space and system cost. Advantageously, the monolithic silicon can be configured to operate in any of the modes described above. Measurement accuracy is also improved. Due to the ratiometric scaling at the output in the single-ended mode and the unipolar ratio mode, the error between the reference voltage of the host system and the DAC reference voltage of the isolation amplifier can be suppressed or eliminated. The gain and gain drift errors of the signal chain are defined only by the input side circuit of the isolation amplifier.

[0045] The term "coupled" is used throughout this specification. The term and its derivatives may cover connections, communications, or signal paths that achieve a functional relationship consistent with this specification. For example, if device A provides a signal to control device B to perform an action, then in the first instance, device A is coupled to device B, or in the second instance, if the intermediate component C does not substantially change the functional relationship between device A and device B, then device A is coupled to device B through the intermediate component C, so that device B is controlled by device A via the control signal provided by device A.

[0046] A device "configured to" perform a task or function may be configured (i.e., programmed and / or hardwired) to perform the function when manufactured by a manufacturer, and / or may be configured (or reconfigurable) by a user after manufacture to perform the function and / or other additional or alternative functions. Configuration may be performed through firmware and / or software programming of the device, through the construction and / or layout of the device's hardware components and interconnects, volatile or non-volatile memory elements, or a combination thereof.

[0047] As used herein, the terms "terminal" and "pin" also encompass "node", "interconnection" and / or "lead". Unless specifically stated to the contrary, these terms generally mean an interconnection or an end thereof between device elements, circuit elements, integrated circuits, devices or other electronic or semiconductor components.

[0048] A circuit or device described herein as including certain components may actually be adapted to be coupled to those components to form the described circuit system or device. For example, a structure described as including one or more semiconductor elements (e.g., transistors), one or more passive elements (e.g., resistors, capacitors, etc.), and / or one or more sources (e.g., voltage sources and / or current sources) may actually include only semiconductor elements within a single physical device (i.e., a semiconductor die and / or an integrated circuit (IC) package), and may be adapted to be coupled to at least some of the passive elements and / or sources to form the described structure at the time of manufacture or after the time of manufacture, for example by an end user and / or a third party.

[0049] Although the use of n-channel MOSFETs is described herein, other types of transistors (or equivalent devices) may be used alternatively or in combination.The circuits described herein may be reconfigured to include replacement components to provide functionality at least partially similar to that available before component replacement.

[0050] The use of the phrase "ground" in the foregoing description includes chassis ground, ground line ground, floating ground, virtual ground, digital ground, common ground, and / or any other form of ground connection that is applicable or suitable for the teachings of this specification. Unless otherwise stated, "about," "approximately," or "substantially" preceding a value means + / - 10% of the stated value.

[0051] Modifications of the described examples are possible, as are other examples, within the scope of the claims.

Claims

1. A reconfigurable filter comprising: a first input and a second input adapted to receive an input signal; a fully differential amplifier (FDA) having an inverting input, a non-inverting input, an inverting output, and a non-inverting output, the inverting input being coupled to the first input and the non-inverting input being coupled to the second input; a first reconfigurable resistor-capacitor (RC) network coupled to the non-inverting output; and a second reconfigurable RC network selectively coupleable to the inverting output; The reconfigurable filter is configurable to enable operation in any one of a plurality of modes including a single-ended operation mode and a differential operation mode.

2. The reconfigurable filter according to claim 1, further comprising: a first input resistor coupling the first input to the inverting input of the FDA; and a second input resistor coupling the second input to the non-inverting input of the FDA, Wherein the first reconfigurable RC network is coupled across the first input resistor and the second reconfigurable RC network is coupled across the second input resistor.

3. A reconfigurable filter according to claim 2, wherein the first reconfigurable RC network includes a first capacitive element coupled between the non-inverting output of the FDA and the inverting input of the FDA, and a first resistive element coupled between the non-inverting output of the FDA and the first input of the reconfigurable filter. The reconfigurable filter of claim 3, wherein the second reconfigurable RC network comprises a second capacitive element selectively coupleable between the inverting output of the FDA and the non-inverting input of the FDA, and a second resistive element selectively coupleable between the inverting output of the FDA and the second input of the reconfigurable filter. The reconfigurable filter according to claim 1, further comprising: a switching mechanism configured to selectively couple the second reconfigurable RC network to the inverting output of the FDA, the switch mechanism is configured to be arranged in a first configuration to provide a differential output signal at an output terminal of an amplifier associated with the reconfigurable filter and a multi-function terminal, the output terminal being coupled to the non-inverting output of the FDA and the inverting output being coupled to the multi-function terminal, and The switch mechanism is configured to be arranged in a second configuration to provide a single-ended output signal at the output terminal and to decouple the multi-function terminal from the inverting output of the FDA and to enable the multi-function terminal to receive a reference voltage signal. The reconfigurable filter of claim 5, wherein the switching mechanism comprises a plurality of switches within the FDA to selectively activate and deactivate the inverted output of the FDA.

4. The reconfigurable filter of claim 5, wherein the switching mechanism comprises a switch configured to selectively couple the inverted output of the FDA to the multi-function terminal.

5. The reconfigurable filter of claim 5, wherein the first reconfigurable RC network, the second reconfigurable RC network, and the switching mechanism are configurable in a first setting to provide a single-ended output signal at the output terminal in the single-ended operating mode.

6. A reconfigurable filter according to claim 8, wherein the first reconfigurable RC network, the second reconfigurable RC network and the switching mechanism are capable of being configured in a second setting to provide a differential output signal at the output terminal and the multi-function terminal in the differential operating mode.

7. The reconfigurable filter of claim 1 , further comprising: A variable resistor is coupled between the second input and ground, the resistance of the variable resistor being set based on a selected operating mode.

8. The reconfigurable filter of claim 4, wherein: The first capacitive element includes a plurality of first output capacitors and a first output capacitive switch; The first resistance element includes a plurality of first output resistors and a first output resistance switch; The second capacitive element includes a plurality of second output capacitors and a second output capacitive switch; and The second resistance element includes a plurality of second output resistors and a second output resistance switch.

9. A system comprising: a digital-to-analog converter (DAC) having a digital input, a DAC reference voltage input, a first output, and a second output; and a multiple feedback (MFB) filter having first and second inputs coupled to the first and second outputs of the DAC, respectively, the MFB filter comprising a fully differential amplifier (FDA) having an inverting input, a non-inverting input, an inverting output, and a non-inverting output, the inverting input being coupled to the first input, and the non-inverting input being coupled to the second input; and a plurality of terminals including an output terminal, a multi-function terminal, a voltage supply terminal, and a ground terminal; The MFB filter can be configured to enable the amplifier of the system to operate in any one of a plurality of modes including a single-ended operation mode and a differential operation mode.

10. The system according to claim 12, wherein: In the single-ended operating mode, the MFB filter is configured to generate a single-ended output signal at the output terminal.

11. The system of claim 13, wherein the single-ended output signal is referenced to a voltage at the multi-function terminal.

12. The system according to claim 12, wherein: In the differential operating mode, the MFB filter is configured to generate a differential output signal at the output terminal and the multi-function terminal.

13. The system of claim 13, wherein the MFB filter is configurable to scale the single-ended output signal using a reference voltage signal input to the multi-function terminal, the generated single-ended output signal being based on an input voltage to the system and a difference between the reference voltage signal and a ground voltage.

14. The system of claim 13, wherein the single-ended output signal is suitable for input to a single-ended input analog-to-digital converter.

15. The system of claim 12, further comprising: a multiplexer having a first input coupled to the multi-function terminal and configured to receive a first reference voltage signal, and a second input coupled to a reference voltage source and configured to receive a second reference voltage signal; and A buffer has an input coupled to the output of the multiplexer, and an output coupled to the DAC reference voltage input.

16. A method comprising: controlling a first reconfigurable resistor-capacitor (RC) network of a filter of an amplifier to set the amplifier in a selected operating mode among a plurality of operating modes; controlling a second reconfigurable RC network of the filter to set the amplifier in the selected operating mode; selecting a source of a reference voltage input to a digital-to-analog converter (DAC) of the amplifier based on the selected operating mode; and An output signal is generated by the amplifier according to the selected operating mode.

17. The method of claim 19, wherein the controlling of the first reconfigurable RC network comprises: controlling a first switch associated with a resistive element of the first reconfigurable RC network to set a resistance thereof; and A second switch associated with a capacitive element of the first reconfigurable RC network is controlled to set a capacitance thereof.

18. The method of claim 20, wherein the controlling of the second reconfigurable RC network comprises: controlling a third switch associated with the resistive element of the second reconfigurable RC network to set the resistance thereof; and A fourth switch associated with the capacitive element of the second reconfigurable RC network is controlled to set the capacitance thereof.

19. The method of claim 19, wherein the selecting of the source of a reference voltage input to a digital-to-analog converter (DAC) of the amplifier comprises: Switches of the filter are controlled based on the selected operating mode to configure terminals of the amplifier as output terminals or input terminals.

20. The method of claim 19, further comprising: setting a variable resistor of the filter based on the selected operating mode, The filter is a multiple feedback filter.

21. The method of claim 19, further comprising: setting a variable resistor of the filter based on the selected operating mode, The amplifier is an isolation amplifier.

Images