Page 149 – Electronics-Lab.com

The Negative Feedback in Electronics

Introduction

According to Norbert Wiener, the American mathematician and the father of cybernetics, feedback is a method of controlling a system by reinserting the results of its past performance into it. In a feedback system, a signal that is proportional to the output is fed back to the input and combined with the input signal to produce the desired system response. Harold Black, an American electrical engineer, invented the negative feedback amplifier in 1927.

Feedback comes in two varieties: positive, and negative. Negative feedback is a connecting technique where some of the output signal (e.g. voltage) is sent back to the inverting terminal and then it is added to the input signal there. It means the signal fed back from the output to the input is 180° out of phase with the applied excitation in the input. This feedback signal can be “sent” back through a resistor, capacitor, complex circuit, or simply through a wire.

A typical feedback block diagram is shown in Figure 1. The input signal V_s is applied to a summing circuit, where it is combined with a feedback signal V_f. The difference of these signals (V_s – V_f) as V_i then becomes the input voltage to the amplifier network with the gain of ‘A’. A portion of the amplifier output V_o is connected to the feedback network ‘β’, which provides a reduced portion of the output as a feedback signal to the input summing circuit.

Figure 1: Block diagram of a feedback amplifier system

We can write the Equation 1 as the total transfer function or feedback amplifier gain in terms of frequency for this configuration:

Equation 1: Feedback amplifier transfer function

where the product of A(jω)β(jω) is called the loop gain.

Effect Of Negative Feedback On Gain And Bandwidth

While positive feedback drives an amplifier circuit toward a point of instability (oscillations), negative feedback drives it toward a point of stability. An amplifier circuit equipped with some amount of negative feedback is not only more stable, but it distorts the input waveform less and is generally capable of amplifying a wider range of frequencies. The trade-off for these advantages is decreased gain.

So, The net result of negative feedback is stability in the amplifier characteristics. Negative feedback may also prevent a transistor/ op-amp amplifier circuit from thermal runaway. Negative feedback also has the advantage of making amplifier total gain more dependent on resistor values and less dependent on the characteristics of semiconductor elements.

In Equation 1, the overall gain with negative feedback is shown. In the condition that the loop gain is large enough, the expression of the formula becomes simplified as shown in Equation 2:

Equation 2: Conditional expression of the total gain

As long as βA >> 1, the overall gain is approximately 1/β. the gain or transfer function of the feedback amplifier essentially becomes a function of the feedback network only. This part of the system can be a very simple resistive circuit, as a voltage divider.

In some of the active amplifier circuits, the individual parameters may vary widely depending on frequency and temperature. It means the value of open-loop gain ‘A’ is not constant in time. But, in a purely resistive feedback circuit, the feedback network gain ‘β’ can be constant. Thus, the overall gain with feedback is not dependent on temperature or frequency and changes in internal components cause little effect on the output. This makes an amplifier stable and easy to design.

Similarly, the frequency distortion because of varying amplifier gain with frequency is considerably reduced in a negative feedback amplifier circuit. It means feedback causes a Reduction in Frequency Distortion.

In fact, as more negative feedback is used, the resultant characteristics of the amplifier (whole system) become less dependent on the characteristics of the no-feedback amplifier (open-loop system) and finally depend on the properties only of the feedback network itself.

Figure 2: Increasing bandwidth in feedback amplifier

As a matter of fact, the gain-bandwidth product of the basic amplifier is the same value as the feedback amplifier. It is also interesting to note that although the use of feedback has the result of lowering the gain, it provides an increase in bandwidth particularly. It means the range of frequencies the amplifier can operate is extended in the feedback system. Figure 2 shows that the amplifier with negative feedback has more bandwidth (BW_f) than the amplifier without feedback (BW₀), while its gain has decreased from A₀ to A_f0.

Reduction Of Nonlinear Distortion

Distortion in an output signal is caused by a change in the basic amplifier gain or the slope of its transfer function. The change in gain can be a function of the nonlinear properties of semiconductor components used in the basic amplifier.

According to Figure 1 configurations, ‘A’ (in simple notation without the argument), is the gain of the amplifier stage alone and without feedback. With feedback β, the overall gain of the circuit is reduced by a factor (1 + βA). Negative feedback has a “damping” effect on an amplifier: if the output signal becomes increased in magnitude, the feedback signal introduces a reversed influence into the input of the amplifier, thus decreasing the change in the output signal. For this reason, in a feedback system, the output changes with fewer variations for a given input signal than without feedback. The term (1 + βA) is also called the desensitivity factor.

Naturally, any real amplifier transfer function has changed in gain but, whereas the open-loop gain ‘A’ changes by a large factor, the closed-loop gain {A/ (1 + βA)} changes by only some percent. A smaller change in overall gain means less distortion in the output signal of the negative feedback amplifier and possibly having near-ideal linearity.

Let us consider a numerical example. If the value of ‘A’ equals 100,000 and the value of ‘β’ equals 0.01, then the overall gain of the feedback system will be:

A_f = A/ (1 + A. β) = 100,000 / [1 + (100,000)(0.01)] = 99.90

Now, if the value of A changes to 150,000, then we will have:

A_f = A/ (1 + A. β) = 150,000 / [1 + (150,000)(0.01)] = 99.93

It shows clearly that by 1.5 times changing the value of open-loop gain (50 % increasing), the value of closed-loop gain has been changed by 3 % only!

Figure 3: comparison between transfer functions of a system with and without feedback

Figure 3 roughly (not in scale) shows the comparison between the transfer functions of an open-loop system (blue curve) and a closed-loop system (green curve). While the gain of the open-loop system has a big change from A₀ to A₁, the gain of the feedback system changes from A_f0to A_f1more smoothly.

Reduction Of Noise Sensitivity

In any electronic system, unwanted random and irrelevant signals may be present in addition to the desired signal. These random signals are usually called noise. Electronic noise can be generated within an amplifier or may enter the amplifier along with the input signal. The noise produced within an amplifier can be reduced by the factor (1 + βA) for considerable improvement. On the other hand, it may increase the signal-to-noise ratio (SNR) at the output of the system.

More precisely, feedback can help reduce the effect of noise generated in an amplifier (such as power-supply hum), but it cannot reduce the effect when the noise is part of the input signal. A large signal-to-noise ratio obviously allows the signal to be detected without any loss of information. This is a desirable characteristic.

The output signal-to-noise ratio is defined in Equation 3, where S_o is the power of desired output signal and N_o is the power of the noise (unwanted) signal at the output.

Equation 3: Definition of signal-to-noise ratio

Feedback Connection Types

There are four basic ways of connecting the feedback signal. These designations correspond to the input- and output-port connections, respectively, between the feedback network and the basic amplifier. Both voltage and current can be fed back to the input either in series or parallel. Specifically, there can be:

Voltage-series feedback (Figure 4 a).
Voltage-shunt feedback (Figure 4 b).
Current-series feedback (Figure 4 c).
Current-shunt feedback (Figure 4 d).

The first term refers to the connection at the output, and the second term refers to the connection at the amplifier input. In the list above, voltage refers to connecting the output voltage as input to the feedback network while current refers to tapping off some output current through the feedback network. Also series refers to connecting the feedback signal in series with the input signal voltage while shunt refers to connecting the feedback signal in shunt (parallel) with an input current source. The type of connection determines which parameter (voltage or current) is sampled at the output and which parameter is amplified. Impedance levels decrease when networks are connected in parallel and increase when they are series-connected.

The connections also determine the feedback amplifier characteristics—in particular, the input and output resistances. The resistance parameters become an important circuit property, when, for example, we consider voltage amplifiers versus current amplifiers.

The topology of the feedback system can change the characteristics of the whole network in comparison to the basic amplifier network alone. Feedback offers the designer the choice of different specifications without changing the parameters of the basic amplifier stage.

Input And Output Impedances With Feedback

A summary of input and output impedances with feedback configurations in Figure 4 is provided in Table 1. The source and output signals in the table are referred to as the feedback stage (circuit) while input and output impedances are referred to as the overall network.

Table 1: Properties of feedback amplifier configurations

It is clear that series feedback connections tend to increase the input resistance, whereas shunt feedback connections tend to decrease the input resistance. Voltage feedback tends to decrease the output impedance, whereas current feedback tends to increase the output impedance. The factor by which the impedance changes is (1 + βA).

A Practical Example Of Using Op-amps (Operational Amplifiers) In Feedback Systems

The name operational amplifier, or op-amp, came into being to describe the fact that these amplifiers were used to create circuits in analog computers, performing some operations like multiplication, differentiation, and so on. Ideal operational amplifiers are typically modeled with very high (ideally infinite) input impedance and very low (ideally zero) output impedance and specifically with very high (ideally infinite) open-loop voltage gain. The trick to making op-amps useful and practical devices involves applying negative feedback. When voltage is “fed” back from the output terminal to the inverting terminal, the gain of an op-amp can be controlled and reduced to reasonable levels. This feedback information specifically tells the op-amp to readjust its output voltage to a value determined by the resistance of the feedback resistor.

The basic circuit connection using an op-amp is shown in Figure 5.

Figure 5: A basic feedback connection using an op-amp

To achieve loop-gain of larger than 1, we should set β less than 1. The type of configuration of this circuit is a voltage-series feedback connection. In the set of Equations 4, the relationship between parameters are expressed. V_o is the op amp’s output voltage as a function of its input voltages V₊(noninverting) and V_–(inverting) and of its open-loop voltage gain ‘A’ (Equations 4-a). The high gain of the op-amp ‘A’ without feedback, is reduced by the feedback factor of β which is calculated for a simple resistive voltage divider (Equations 4-b). Finally, Equation 4-c shows the overall voltage gain with feedback based on values of 2 resistances.

Equation 4: Sets of relations about the feedback op-amp circuit

Let us consider a numerical analysis. If we have A = 100,000 as the open-loop gain, and R_f= 2 kΩ and also R_i = 200 Ω, then we can find the parameters as:

β = feedback factor= 200 / (2000 + 200) = 0.09

βA = loop-gain = (0.09)(100,000) = 9000

A_f = close-loop gain = 100,000 / (1 + 9000) = 11.10

Note that since βA >> 1, we can also calculate with suitable approximation:

Af ≈ 1/ β = 11.11

It is obvious that two simple resistors control the gain of this circuit. The op-amp circuits are sometimes easier to analyze and calculate than transistor amplification circuits.

Summary

The feedback process takes a portion of the output signal and returns it to the input to become part of the input excitation.
Negative feedback is implemented simply by coupling the output back in such a way as to cancel some of the input signals.
Negative feedback has some advantages as follows:
- Better stabilized voltage gain (self-stabilizing); Variations in the circuit transfer function (gain) as a result of changes in transistor parameters are reduced by feedback. It means circuit performance is insensitive to manufacturing and environmental changes. This is one of the most attractive features of negative feedback.
- Improved frequency response (bandwidth improvement); The bandwidth of a circuit that incorporates negative feedback is larger than that of the basic amplifier.
- Higher input impedance and lower output impedance (control of impedance levels); The input and output impedances can be increased or decreased with the proper type of negative feedback circuit.
- Reduced noise (Noise sensitivity reduction); Negative feedback may increase the output signal-to-noise ratio if noise is generated within the feedback loop.
- More linear operation and lower distortions (Reduction of nonlinear distortion); Since transistors have nonlinear characteristics, distortion may appear in the output signals, especially at large signal levels. Negative feedback reduces this distortion.
Negative feedback also has some disadvantages:
- Circuit gain. The overall amplifier gain, with negative feedback, is reduced compared to the basic amplifier used in the circuit.
- Instability condition. There is a possibility that the feedback circuit may oscillate especially at high frequencies.

Two-Port Parameters and Transformations

Introduction

A linear circuit is one whose output signal is linearly proportional to its input signal. As a simple case, it is possible to model the network at only two terminals as shown in Figure 1. Here, only V₁ and I₁ as the voltage and the current internal to the circuit, need to be described. A pair of terminals through which a current may enter or leave a network is known as a port. As shown in Figure 1, the current I₁which enters one terminal ‘a’, equals the current leaving the other terminal ‘b’. Two-terminal devices or elements (such as resistors, capacitors, and inductors) can be characterized as one-port networks.

Figure 1: Representation of a one-port linear network

To establish a mathematical model for the network at the defined port, two further restrictions should be considered: (1) all external connections to the circuit, such as sources and impedances, are made at the port and (2) the network can have internal dependent sources, but not independent sources. Then, with the logical assumption of (I_a = I_b = I), we can rewrite Ohm’s law for this port as shown in Equation 1:

Equation 1: Ohm’s law applied to the terminals ‘ab’

where Z is the impedance and Y is the admittance of the network at the port. In a mathematical model, the various terms that relate the voltage and the current are called parameters. Z and Y are parameters which can be in the form of Laplace transforms [Z(s) and Y(s)], sinusoidal steady-state functions [Z(jω) and Y(jω)], or simply constant resistive terms.

Generally, to analyze a linear electric circuit, Thévenin’s and Norton’s theorems can be used to produce a simplified behavior model of an electric/electronic network as viewed from the selected terminals. These theorems provide techniques by which the real network is replaced by an equivalent circuit. Figure 2 reviews these theorems. You can also find details about the theorems in the links attached.

Figure 2: Reviewing of Thévenin’s and Norton’s theorem

Each circuit normally accepts an input signal at a set of terminals and produces an output signal at a set of other terminals. Basically, a two-port network has two terminal pairs acting as access points, as shown in Figure 3, the current enters one terminal of each pair, ‘a’ and ‘c’, and leaves the other terminal in each pair, ‘b’ and ‘d’. Here we see the input port, represented by V_ab and I_a(or I_b), and the output port, represented by V_cd and I_c(or I_d). It should be noted that the representation of currents and voltage in two ports are based on sign conventions in electrical circuits. The same restrictions about external connections and internal sources mentioned above for the single port systems are also applied.

Figure 3: Representation of a two-port linear network

For example, a bipolar transistor as a three-terminal device in a common-emitter configuration can be used as a linear amplifier, has an input port between its base and emitter (V_be and I_b) and an output port between the collector and emitter (V_ce and I_c); as shown in Figure 4. Essentially, the transistor action can be described such that the voltage across two terminals (base and emitter) controls the current in the third terminal (collector). We can also apply the two-port system model (Figure 3) in such circuit. This is also applicable to other electronic active or passive devices like op-amps and transformers.

Figure 4: A single-stage amplifier using BJT as a two-port circuit

Mathematical demonstration of two-port networks is important because such circuits are used in huge applications like communications, control, and power systems. Additionally, knowing the parameters of a two-port network enables us to consider it as a black box when embedded within a larger network i.e., this reduces the analysis complexity.

Mathematical Modeling Of Two-port Networks Based On Z-parameters

There are many options to establish a model. Here, just the z-parameter (impedance) technique is introduced. In order to produce a mathematical model of circuits represented by a two-port linear network, we must find relationships between voltages and currents. Let us visualize placing two voltage sources at the input and the output, as shown in Figure 5. Thus, we have selected two of the variables, V₁and V₂. We call these variables the independent variables. The remaining variables, I₁ and I₂, are dependent upon the selected applied voltages. We call I₁ and I₂ the dependent variables. (Also it is possible to imagine there are 2 current sources placed in the input and output ports i.e., the type of variables will be interchanged).

Figure 5: A linear two-port network driven by voltage sources (top) and current sources (bottom)

To analyze the system, we use the principle of superposition which states: The response of a linear circuit excited by multiple independent input signals is the sum of the responses of the circuit to each of the input signals alone. Using superposition method, we can write each dependent variable as a function of independent variables as follows in Equation 2:

Equation 2: Mathematical model of a two-port network via z-parameters

In Equation 2, the coefficients of z_ij are called as parameters of the two-port network. These parameters can be calculated by setting input port or output port in open-circuited condition i.e., by disconnecting sources simply. Equation 3 shows the set of equations which used for computation. Since the parameters are found by setting port currents, I₁ or I₂, equal to zero, they are called open-circuit parameters. Also, since the definitions of the parameters as shown in Equation 3 are the ratio of voltages to currents, they are referred as impedance parameters, or z-parameters.

By these definitions we can call z-parameters new characteristics:

z₁₁ as the input impedance of the linear network;
z₁₂as the transfer impedance from port 1 to port 2;
z₂₁as the transfer impedance from port 2 to port 1;
z₂₂as the output impedance of the linear network.

Many real two-port networks appear in the configuration like Figure 6 in which one port delivers energy by voltage or current sources i.e., the excitation is generally applied at this input port, and the other port consumes energy i.e., it normally extracts the desired signal by a load. The symbol of Z_S indicates the internal impedance of the voltage source and Z_L indicates the impedance of the external electrical load.

Figure 6: A typical model for real two-port networks configuration by a source and a load

Equation 4: Network voltage gain and current gain definitions

In such configurations, which are very common in amplifier systems, it is possible to define the gain of voltage (or current) between input and output ports. we can specify two important definitions for gains of the two-port network as shown in Equation 4. In this set of equations, A_vstands for network (open-circuit) voltage gain and A_istands for network (short-circuit) current gain.

The amplifiers take power from an external source of energy (normally a DC power supply) and use it to boost the input signal. Finally, the amplifier delivers an output signal whose waveform corresponds to the input signal but its power level is higher. The output waveform of an amplifier must be an exact duplication of the input waveform. It preserves the details of the signal waveform and any deviation of the output waveform from the shape of the input waveform is considered as distortion.

Frequency Response Of A Two-port Network

The frequency response characteristics of a system can be found directly from its transfer function. Normally in each amplifier the response of gain magnitudes, |A(jω)|, verses frequency ranges can be plotted in logarithmic scale similar to the graph in Figure 7. The values of amplitude are in terms of Decibels (dB) and frequency values are measured in Hertz (Hz).

Figure 7: Typical two-port network frequency response

For a practical amplifier the gain drops off at high frequencies due to the active device and circuit capacitances. Gain may also drop off at low frequencies for capacitive coupled amplifier stages. Three frequency ranges are indicated in the Plot: low, midband and high frequency ranges. If the linearity would be critical in the performance of the system, the ideal operating region could be between frequencies of f₁ and f₂, in the midband range, because of perfect flat response. But, for most of amplifier systems the operation between frequencies of f_L and f_H would be acceptable, where the gain of the system is almost constant. The value of gain at f_L and f_H is 3 dB less than the maximum midband gain (0 dB in the graph). f_L and f_H are called the lower and upper corner (cut-off) frequencies, respectively. The Bandwidth of the amplifier stage is the difference between these 2 high and low frequencies as shown in Equation 5.

There is a Figure of Merit applied to amplifiers called the Gain-Bandwidth Product (GBP) that is commonly used to initiate the design process of an amplifier. It provides important information about the relationship between the gain of the amplifier and the expected operating frequency range.

Equation 5: Definition of Bandwidth and GBP

Summary

Many networks can be considered as having two pairs of terminals: a pair of input terminals at which the excitation is usually applied, and a pair of output terminals at which the desired signals are extracted. Because the system behaves linearly, the variables are related by a set of linear equations. These equations relate the port currents and voltages and define a set of two-port parameters.
The functions of each two-port linear network can be described with mathematical models based on measures of each terminal. One of the simple and well-known models is the z-parameters model which is based on impedance parameters between terminals of the network.
Voltage and current gains are also defined for linear two-port networks.

Infineon presents the world’s first ISO26262-compliant high-resolution 3D image sensor for automotive

Posted on 10 June, 202210 June, 2022 by mixos

Innovative car cockpits, seamless connectivity with new services, and improved passive safety: 3D depth sensors play a key role in monitoring systems in the vehicle cabin. They are essential to meet regulations as well as NCAP ratings and to realize the vision of the driver becoming a passenger. Infineon Technologies AG , in collaboration with 3D time-of-flight system specialist pmdtechnologies ag, has therefore developed the second generation of the REAL3™ automotive image sensor – an ISO26262-complient high resolution 3D image sensor.

“Leveraging our leadership in 3D sensors for consumer applications, we are now offering high resolution with a tiny image circle to the automotive world. This enables cars with functions from the consumer world, while maintaining automotive standards and even improving passive safety,” said Christian Herzum, Vice President 3D Sensing at Infineon. “For instance, reliable and secure facial authentication allows seamless connectivity for any type of service that requires authentication such as payment, battery charging or accessing private data.”

In addition, the same camera meets all requirements for driver monitoring to detect driver distraction and fatigue. This enables the offering of a driver monitoring system with secure 3D facial recognition using only one ToF camera.

“From the start we were focussed on improving the robustness of the underlying pmd-based ToF Technology against external influences such as sunlight or other disturbing light sources. For this reason, the new imager shows excellent and cutting edge performance even under harsh conditions”, said Bernd Buxbaum, CEO pmdtechnologies ag.

The sensor comes in a 9 x 9 mm² plastic BGA package and offers a VGA system resolution of 640 x 480 pixels with a tiny image circle of 4 mm. This allows lens sizes similar to those known from smartphones, but now also for automotive applications. The high resolution of the REAL3 sensor also makes it suitable for camera applications with a wide field of view, such as complete front-row occupant monitoring systems. The resulting 3D body models enable accurate estimates of occupant size and weight, as well as highly precise passenger and seat position data, which is key information for intelligent airbag deployment and restraint systems. In addition to its small size, the single-chip solution is qualified to AEC-Q100 Grade 2 and is the first of its kind being developed according to the ISO26262 (ASIL-B) standard.

Besides safety critical applications, the 3D data allows for comfort features such as gesture control or intuitive interior lighting that follows passengers’ movements. Additionally, the imager might be used in environmental perception scenarios as a Flash-LiDAR in the automotive space and – based on the safety conformity – it is also an ideal candidate for adjacent applications in mobile robotics, drones and other autonomous use cases in general where reliability and safety is a must to protect operators.

Depth sensor technology from Infineon and pmd

The time-of-flight technology of the depth sensor is the basis for a wide range of use cases. It provides highly reliable distance information and at the same time a 2D grayscale image of the entire scene under all ambient light conditions – at night, in sunlight, and under heavily changing lighting conditions.

Availability

Development samples of the new 3D image sensor chip (IRS2877A) are available now and series production has begun. The ISO26262 compliant variant IRS2877AS will be available for series production by the end of 2022.

More information is available at www.infineon.com/real3-automotive.

Monolithic Power Systems (MPS) MP3363 Boost LED Drivers

Posted on 10 June, 2022 by mixos

Monolithic Power Systems (MPS) MP3363 Boost LED Drivers offer an ideal solution for low-current and high-current boost applications. The MP3363 provides a low 0.2V feedback voltage (VFB), allowing higher efficiency in white LED driver applications. The device regulates the output voltage (VOUT) up to 36V, with an efficiency as high as 95%. Additionally, the current mode regulation and external compensation components permit the MP3363 control loop to be optimized across a wide variety of input voltages.

The MPS MP3363 Boost LED Drivers deliver analog dimming and pulse-width modulation (PWM) dimming on the same pin. An input PWM signal with a dimming frequency below 2kHz initiates PWM dimming, while an input PWM signal with a dimming frequency above 5kHz initiates analog dimming.

The MP3363 drivers implement many protection features, including soft start, cycle-by-cycle current limit, and input under-voltage lockout (UVLO) protection that prevents the sensitive external circuitry from being damaged or overstressed during start-up or potential overload current conditions.

The MP3363 Boost LED Drivers are housed in a TSOT23-8 package.

Features

Wide 1.8V to 36V input voltage range
1A Peak current limit
0.5μA Shutdown current
Low 200mV Feedback Voltage (V_FB)
200kHz to 2.2MHz Configurable Switching Frequency (f_SW)
Internal 100mΩ, 40V power switch
High efficiency
Analog dimming and Pulse-Width Modulation (PWM) dimming
Under-Voltage Lockout (UVLO) Protection
Open/Short LED protection
Short FB to GND protection
Soft start
Thermal Shutdown (TSD)
Available in a TSOT23-8 package

more information: https://www.monolithicpower.com/en/mp3363.html

Melexis MLX90397 Micropower Triaxis 3D Magnetometer

Posted on 10 June, 2022 by mixos

Melexis MLX90397 Micropower Triaxis® 3D Magnetometer is a position sensor IC featuring Triaxis® Hall Technology and optimized for battery-powered designs. The MLX90397 measures magnetic fields along the three axis X, Y, and Z (Y being in a plane parallel to the surface of the die, Z being perpendicular to the surface). These measurements and the IC temperature are converted into 16-bit words, which are transferred upon request over an I²C communication channel. The device transmits compensated raw measurement data of the selected Bx, By, Bz, or a combination. The MLX90397 is designed for position sensor applications with a ±50mT range and an adaptative range on Bz of ±200mT.

The Melexis MLX90397 Micropower Triaxis 3D Magnetometer is housed in a compact 2.0mm x 2.5mm UTDFN-8 package ideal for space-constrained applications.

Features

3-axis magnetometer device suitable for position sensors applications Triaxis® (Hall Technology)
Low power operation
- 7nA typical idle mode current
- 1.7V to 3.6V supply voltage
Compatible with I²C (0.1MHz, 0.4MHz, or 1MHz)
Digital 16-bit output
- 16-bit magnetic (XYZ)
- 16-bit temperature
At runtime selectable modes
- Magnetic axis selection
- Single measurement
- Continuous mode up to 1.4kHz (XYZ)
Low 2µT noise for a 50mT range
Ambient temperature range from -40℃ to +105℃
2.0mm x 2.5mm x 0.4mm UTDFN-8 package (JEDEC qualified)
RoHS compliant and “Green” package

Block Diagram

more information: https://www.melexis.com/en/product/MLX90397/Triaxis-ValueOptimized-Magnetometer-micropower-consumer-battery

USB Type-C PD3.0 Sink Controllers Enable Streamlined and Cost-Effective Charging

Posted on 10 June, 2022 by mixos

Diodes Incorporated (Diodes) (Nasdaq: DIOD) continues to strengthen its portfolio of USB power delivery (PD) solutions by bringing two new high-performance USB PD3.0 sink controller ICs to the market. The DIODES™ AP33771 and DIODES™ AP33772 sink controllers are targeted at home appliances and cordless power tools, enabling the appropriate voltage level to be negotiated via USB-C^®. They have an operating voltage range of 3.3V to 24V.

The AP33771’s simple pin-driven setting of required voltages and power makes it easier to use, while the AP33772 provides greater flexibility for more sophisticated designs that use a µC (with an I²C interface included). Both devices have built-in application firmware, which automatically carries out the PD 3.0 negotiation procedure with the attached USB PD 3.0 compliant charger in order to obtain the required power level. LED lighting (driven by one of their GPIOs) enables a clear indication of the charging state and potential fault situation.

The AP33771 has a preloaded power menu, consisting of eight different output voltages and 10 different power levels. The power requirements of the end equipment can be met via alteration of simple resistor settings. It also provides 5V charging when connected to a classical USB Type-A charger, as well as supporting USB Type-C to USB Type-C cable voltage drop compensation.

The I²C interface on the AP33772 allows more sophisticated system designs to be addressed. Through it, particular power profiles can be specified, as well as enabling access to various protection features.

The AP33771 and AP33772 are supplied in 24-pin W-QFN4040 packages. They are available at $0.5201 in 1000-piece quantities. Evaluation boards are available through Diodes’ sales channel upon request.

Binary Numbers

The binary numbers are expressed in the base-2 number system which has only two (2) distinct number values i.e. 0 and 1. Just like, most common, decimal numbers are expressed in a base-10 number system having ten (10) distinct numbers from 0 to 9. These number systems are designed to express information and binary numbers are used in the digital systems to carry out the flow of information in the form of zeroes and ones.

It is based on Boolean data type which has only two possible values i.e. true and false. It is named after the English mathematician George Boole and is now widely used in all digital systems. The Boolean represents a single bit whereas the binary number may consist of more than a single bit or Boolean value. As already said, a Boolean value may comprise of either “TRUE” or “FALSE” value and these values are also represented by “ON” or “OFF”, and” 1” or “0”, respectively. However, binary numbers are represented in “0” and “1”. In modern digital electronics, communication systems, computers, etc. the flow of information is in binary and a voltage level is designed to distinguish between 0 and 1 values.

The information carried by a digital system is discrete and represents a distinct voltage state or value at any instant of time. Unlike an analog signal or linear system, which has continuously varying values and is usually represented by an instantaneous value. In a digital system, binary values of 0 and 1 are given a voltage level so they can be distinguished during the flow of information. Most commonly, a value of 1 is represented by 5V, whereas, a binary value of 0 is given 0V or ground potential. These binary numbers in digital systems are usually referred to as BITS (Binary DigiTS).

Binary data stream — Figure 1: The binary data stream

The process of information in form of binary numbers or bits requires only two values or voltages and one of them is at ground potential. This requires less circuitry and is ideal for use in digital systems. The binary values can be represented by any voltage and have designated logic levels. For each voltage value, there is a logic level i.e. LOW or HIGH logic. The voltage level is usually kept between 0 and 10V. Generally, a high voltage level represents a HIGH logic level and a low voltage (ground) level represents a LOW logic level.

The electronic circuits are classified into analog and digital circuits depending on the signal type.

Analogue Circuits

The analog circuit uses time-varying continuous signals and covers, theoretically, an infinite range of values over a period of time. The analog circuit can respond to an analog signal over a period of time, accordingly. The signal may cover a voltage range from positive to a negative value.

The following figure illustrates a continuously varying or analog signal behavior over a period of time.

Analogue signal explained — Figure 2: The analogue signal

The output of the signal is taken from the potentiometer whose other ends are connected to extreme levels of the voltages i.e. supply voltage and ground. The knob of the potentiometer is rotated to vary the output resistance from zero to maximum value. The output voltage is obtained using a voltage division rule (VDR) and ranges from zero to supply voltage potential. Whilst slowly rotating the potentiometer’s knob, the output voltage gradually increases from zero to supply voltage potential and at every instant of time, a different value is obtained. Moreover, the gradual increase in output voltage indicates no sudden or step-change between any two periods. The plot of output voltage indicates the same i.e. no step change and is indicative of a continuous or analog signal. Examples of analog signals include sensor outputs from physical outputs such as temperature, light, pressure, distance, liquid levels, etc.

Digital Circuits

The digital circuit uses only two distinctive voltage levels for its HIGH and LOW logic levels. These HIGH and LOW logic levels correspond to the 1 and 0 values of binary, respectively. There will be only two voltage levels corresponding to these logic levels only at any instant or period of time. The voltage level for these logics may be different depending on the circuitry such as Transistor-Transistor Logic (TTL), Complementary Metal Oxide Semiconductor (CMOS), etc.

The digital signal and its discrete voltage levels can be explained by the following figure.

Digital signal explained — Figure 3: The digital signal

The potentiometer of the above circuit has now been replaced with five (5) resistors of equal values. The output voltage is taken from extreme voltages levels (5V and 0) as well as from each junction of resistors. These junctions form the voltage divider circuit and the inclusion of each resistor causes an increase in output voltage. The output voltage stages have been divided into six (6) stages and the knob connects the output to each of the stages sequentially. Moving from stage 1 to stage 6, it is observed that the output voltage suddenly changes at each step and produces a distinctive voltage level that does not vary. The output voltage plot depicts the same i.e. stage change produces a sudden voltage step and each stage has a constant or distinctive voltage level over the period.

It is eminent from the above illustrations that a continuously varying or analog signal is not constant over a period of time and may contain an infinite range of values over a period. In contrast, a digital signal contains distinctive values over a period of time. In order to understand the difference between these two signals, a real-time example of a light dimmer can be taken for an analog signal. The rotation of the light dimmer is continuous and not abrupt. On other hand, a switch (button) controls the light as a digital signal. The switch has only two distinctive states i.e. OFF or ON and the change between them is abrupt.

Most electronic circuits contain both analog and digital circuits dealing with the sensors. The conversion from analog to digital is required to convert sensors, reading data in analog, to digital values using an analog-to-digital converter (ADC). The digital values can be processed in digital systems, easily transmitted, and stored in memory devices. Likewise, a stored digital value from the memory or instruction can be converted to an analog value using Digital-to-Analogue Converter (DAC).

Logic Levels

As discussed above in the article, a binary bit or Boolean value can hold only one of the two possible states i.e. logic 1 or logic 0. Logic 1 and logic 0 are also commonly referred to as ON/ HIGH and OFF/ LOW, respectively. In the following figure, these two states are shown along with simple circuits to achieve these possible states. The most commonly used logic family i.e. TTL uses +5V as indicative of logic 1 value.

Logic states — Figure 4: Possible states of logic levels

Voltage Levels for TTL Devices

The digital logic levels i.e. HIGH and LOW are obtained from the signal voltage level and usually for a logic level a range of voltage is used depending on many factors. In the following figure, the input and output voltage levels of Transistor-Transistor Logic (TTL) are shown.

TTL Voltage Levels — Figure 5: The TTL voltage levels for input and output signals

For the TTL input signals, a maximum of 0.8V is desired in order to ascertain a logic LOW, and a minimum voltage of 2V is desired for a logic HIGH. This means that any logical LOW input needs to have a voltage from 0 to 0.8V and from 2 to 5V for a logical HIGH input. The voltage from 0.8 to 2V is designated as non-usable. Likewise, for a TTL output signal, a logic LOW limit is set to a maximum of 0.4V, and a minimum limit of 2.7V is set for logic HIGH. The voltages falling within these voltage levels will be logically designated as HIGH or LOW depending on the voltage of the signal.

Conclusion

The binary number is a base-2 numbering system in which each successive bit doubles the values of the binary number (power of two).
Each digit of a binary number commonly referred to as bit is of Boolean data type and can hold one of the two possible values i.e. 0 or 1. The values of 0 and 1 are also designated as LOW and HIGH, respectively.
Each successive bit of a binary number doubles the value of the binary number e.g. for 1,2,3,4, and 5 digits binary numbers the decimal value will be 1,2,4,8,16, and 32, respectively.
The electronic circuits can be divided into analog and digital circuits. The analog signal is continuous and contains many values within a time period. Whilst, the digital signal has discrete values and change between these discrete values is sudden or abrupt.
The most commonly used Transistor-Transistor Logic uses voltage levels of 0 and 5V for designating logic LOW and HIGH, respectively.

Dual MOSFET Driver – Two Channel DC SSR Using MOSFETS & Gate Driver

The project presented here is a dual-channel MOSFET DC relay. The project is capable of driving a 5A load on each channel with an input supply of 48V DC. The LTC7067 chip drives the two high-side N-Channel MOSFETS with supply voltages up to 48V DC. Its powerful 0.8Ω pull-down and 1.5Ω pull-up MOSFET drivers allow the use of large gate capacitance and high voltage MOSFETs. Additional features include UVLO, TTL/CMOS compatible inputs, and fault indicator. The optional diodes D2 and D3 can be used for inductive loads. Open-Drain Fault Output is available. The open-drain output pulls to GND during VCC UVLO/OVLO and floating supplies UVLO condition.

Note 1: The project requires dual supply, VCC and VDD, VDD is load supply in the range 12V to 48V, and gate supply 12V to 14V. The board can work with a single supply if the load supply is between 12V to 14V in this case close jumper J1

Note 2: The project can work with a higher load supply up to 140V. In this case, use appropriate MOSFET Q1 and Q2 and choose higher voltage capacitor C2, C3

Note 3: C5, C6, C7 are optional DC Bus capacitors, and can be used as per user’s requirements

Note 4: The project is capable of driving resistive loads. Optional diodes D2, D3 are provided for inductive loads such as motors, solenoids. Recommended diode MBRS360 3A-60V

Features

VDD (Load Supply) 12V to 48V DC
VCC for Gate Driver 12-14V DC
Load 5A Each Channel with Forced Air Cooling (Fan)
On-Board Jumper for 12V-14V Single Supply Operations for Load and Gate Driver
Fault Condition Output Normally High, Goes Low When UVLO/OVLO and Floating Supplies UVLO Condition Occurs
Optional Clamp Diode D2, D3 for inductive Loads
TTL/CMOS Compatible Control Inputs
Input PWM Duty Cycle 0 to 100%
Input Frequency 20Khz-Tested (Supports Higher Frequency)
Under Voltage Lockout
4 x 3MM Mounting Holes
Onboard Power LED
PCB Dimensions 53.98 x 45.09mm

Connections CN3 Connector

Pin1 VDD Load Supply 12V to 48V
Pin2 VCC Gate Driver Supply 12V to 14V
Pin3 Input 1
Pin4 Input 2
Pin5 Fault Output Normally High
Pin6 GND

Other Components Details

Connector CN1 and CN2 Load 1 and Load2
Connector CN3 Load Supply 12V to 48V
LED D1 Power LED
Jumper J1 for Single Supply Operation (Read Note 1)
CN5 Not In use

Schematic

Parts List

NO	QNTY	REF	DESC	MANUFACTURER	SUPPLIER	PART NO
1	2	CN1,CN2	2 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1247-ND
2	1	CN3	6 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5319-ND
3	1	CN4	2 PIN SCREW TERMINAL PITCH 5.08MM	PHOENIX	DIGIKEY	277-1247-ND
4	1	CN5	2 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5315-ND
5	1	C1	10uF/16V SMD 1210 OR 1206	YAGEO/MURATA	DIGIKEY
6	2	C2,C4	0.1uF/50V SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
7	1	C3	220uF/50V SMD ELKTROLYTIC	WURTH	DIGIKEY	732-8463-1-ND
8	5	D2,D3,C5,C6,C7	DNP			READ NOTE
9	1	D1	LED RED SMD SIZE 0805	LITE ON INC	DIGIKEY	160-1427-1-ND
10	1	J1	JUMPER - 2 PIN MALE HEADER PITCH 2.54MM		DIGIKEY	732-5315-ND
11	2	Q1,Q2	IRF540 TO263	INFINION	DIGIKEY	IRF540NSTRRPBFCT-ND
12	1	R1	1K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
13	1	R2	51K 1% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
14	1	U1	LTC7067	ANALOG DEVICE	DIGIKEY	505-LTC7067RMSE#PBF-ND
15	1	J1-S	JUMPER SHUNT	SULLINS CONNECTOR	DIGIKEY	S9001-ND

Connections

Gerber View

Photos

Video

LTC7076 Datasheet

Over Speed Sensor – Over Speed Alarm using Magnetic Pickup Sensor

This is an over-speed sensor module, that provides an audible warning and signals output when the speed of a machine is above a set point. The module can be used in applications such as Engines, Machines, Sports machines, and Fitness Equipment. The speed of the machine or engine can be detected using magnetic pickup sensors. The project can be used in many applications where an over-speed monitor is important. The board is based on the LM2907 chip that works as a frequency to voltage converter, interfacing a magnetic pickup as shown in the figure below. A typical magnetic pickup for automotive applications will provide a thousand pulses per mile so that at 60 mph the incoming frequency will be 16.6Hz. When the reference level on the comparator is set by two equal resistors R2 and R6 then the desired value of C5 and R4 can be determined from the following simple relationship:

The buzzer is energized when Frequency ≥ (1/(2XR4C5))

From the RC selection chart, we can choose suitable values for R5 and C5. With the current circuit, the frequency is set to 500Hz approx. The frequency trigger point can be changed as per user requirement using above equation. The module supports any sensor voltage level from 20mV to 28V.

If you are looking for “Under Speed Warning Alarm for Magnetic Pickup sensor” check the link attached.

RC selection Diagram

Magnetic Pickup Sensor

A Magnetic Pickup Sensor consists of a permanent magnet, a pole-piece, and a sensing coil all encapsulated in a cylindrical case. Magnetic Pickup is most frequently used to sense passing teeth on a gear, sprocket, or timing belt wheel, to bolt-heads, key-ways, or other moving machine-mounted targets.

Connections: CN1

Pin 1 Output Normally Low, Goes High When Over Speed Sense,
Pin 2, Pin5, Pin6 = GND
Pin 3 and Pin 4 = VCC Supply Input

Connections CN2: Magnetic Pick Up Sensor

Features

Supply 12 to 15V DC @ 20mA
Optimized for Magnetic Pickup Sensor
Other Optical Sensor, Mechanical Sensor, and Tachometer sensors can be used
Inputs Voltage Level 20mV to 28V
Buzzer Operates when the Input frequency is above 500Hz
Provide High Output When Speed is below Set Point
Header Connector for Supply Input and Output
2 Pin Header for Sensor
D1 Power LED
PCB Dimensions 38.42 x 16.19mm

Applications

Engines
Tachometer Under/Over Speed
Fitness Equipment
Sports Machines
Machine Automation
AC/DC Motor Speed Monitor

Schematic

Parts List

NO	QNTY.	REF.	DESC.	MANUFACTURER	SUPPLIER	PART NO
1	1	BZ1	BUZZER	CUI DEVICE	DIGIKEY	102-CMI-1295-1285T-ND
2	1	CN1	6 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5319-ND
3	1	CN2	2 PIN MALE HEADER PITCH 2.54MM	WURTH	DIGIKEY	732-5315-ND
4	1	C1	10uF/25V SMD SIZE 1206	YAGEO/MURATA	DIGIKEY
5	1	C2	0.1uF/50V SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
6	1	C3	1uF/25V SMD SIZE 1206	YAGEO/MURATA	DIGIKEY
7	3	C4,R8,R9	DNP
8	1	C5	0.01uF/50V SMD SIZE 1206	YAGEO/MURATA	DIGIKEY
9	1	D1	LED SMD SIZE 0805	LITE ON INC	DIGIKEY	160-1427-1-ND
10	1	Q1	BC847AL	MICRO COMMERCIAL	DIGIKEY	BC847B-TPCT-ND
11	2	R1,R7	1K 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
12	3	R2,R5,R6	5K1 1% SMD SIZE 0895	YAGEO/MURATA	DIGIKEY
13	1	R3	100E 5% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
14	1	R4	100K 1% SMD SIZE 0805	YAGEO/MURATA	DIGIKEY
15	1	U1	LM2907-N	TI	DIGIKEY	LM2907M-8/NOPB-ND

Connections

Magnetic Pickup Sensor

Gerber View

Photos

Video

LM2907 Datasheet

TDK TFM-BLE Thin-Film Power Circuit Inductors

Posted on 9 June, 20229 June, 2022 by mixos

TDK TFM-BLE Thin-Film Power Circuit Inductors utilize a magnetic metal material with high saturation magnetic flux density to meet the DC bias characteristics required by inductors for power circuits. The TFM-BLE Inductors offer mounting stability and can be mounted to general-purpose land patterns, featuring the same footprint and terminal structures as general chip parts. A closed magnetic circuit structure minimizes leakage flux. The TDK TFM-BLE Thin-Film Power Circuit Inductors feature a 0.24µH to 0.47µH inductance range with ±20% tolerance, a typical DC resistance range of 18mΩ to 25mΩ, and a -40°C to +125°C operating temperature range.

Features

Metal magnetic material with high saturation magnetic flux density
Meets DC bias characteristics needed by inductors for power circuits
A closed magnetic circuit structure
Minimized leakage flux
Same product shape and terminal structure as general chip parts
Excellent mounting stability characteristics
Can also be mounted to general-purpose land patterns
Lead-free, Halogen-free, RoHS and REACH compliant

Specifications

0.24µH to 0.47µH inductance range
±20% tolerance
DC resistance ranges
- 18mΩ to 25mΩ typical
- 20mΩ to 29mΩ maximum
1MHz measuring frequency
2.0mm x 1.20mm x 0.8mm in dimension
Temperature ranges
- -40°C to +125°C operating
- -40°C to +85°C storage

more information: https://www.tdk-electronics.tdk.com/en/374108/tech-library/articles/products-technologies/products-technologies/tdk-offers-compact-inductors-with-enhanced-performance-capabilities-to-address-smartphone-power-circuit-demands/3096770