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These engineer-to-engineer and application notes, published within the past 12 months, are listed in chronological order.
The AD8436 complete true rms measurement system-on-a-chip comprises three independent circuit blocks. Its rail-to-rail field effect transistor (FET) input amplifier, high dynamic range, true zero rms computing core, and precision rail-to-rail output amplifier facilitate measurement systems that operate from high-impedance voltage sources in the megohm range to deliver high-accuracy dc output voltages equivalent to the rms value of applied input voltages. This 16-page Application Note explores configuration options for the AD8436.
This 4-page Application Note provides a guide to the ADM1278 Hot Swap Designer Excel-based design tool, which allows a designer to enter system specifications and then compute the undervoltage threshold, overvoltage threshold, current limit, and other settings.
The growing demand for compact size in the power supply industry is forcing the size of power supply units to decrease. In addition to the power level, the size of the power supply is determined by the switching frequency and efficiency. The switching frequency determines the size of the transformer and the inductor, while the efficiency determines the size of the switches and board, which can be bulky. This 6-page Application Note details the setup of the PWMs in the full-bridge phase-shifted topology and explores the adaptive dead time feature of the ADP1055 digital controller that enables zero-voltage switching at light loads.
The ADE7932/ADE7933/ADE7978 isolated metering chipset targets polyphase energy metering applications that use shunt current sensors. This 13-page Application Note expands on the information found in the ADE7932/ADE7933/ADE7978 data sheet, providing in-depth explanations of how to use the chipset when developing a direct, 3-phase meter with shunts.
When the ADF7024 integrated transceiver receives a packet, it stores the data in a linear sequence in the packet RAM. Prior to transmission, the data to be transmitted is written to the packet RAM in a linear sequence. This functionality is described in the ADF7024 Reference Manual, UG-698. The packet RAM is 240 bytes long. If the packet length is greater than 240 bytes, additional measures are required. This 3-page Application Note describes a method for handling longer packet lengths, up to a maximum length of 65,535 bytes, via a rolling buffer.
A 3-phase 4-wire (3P4W) wye configuration includes three phase wires and one neutral wire. Each phase voltage is measured with respect to the neutral. The phase voltages are typically 220 V rms or 110 V rms, with each phase voltage phase-shifted 120° with respect to the others. Attenuation networks are commonly used on each of the 3-phase wires to step down the 220 V/110 V signals into signals small enough to enter the ADExxxx metering IC. The neutral wire is typically used as the ground reference. In certain cases, however, the neutral cannot be treated as the ground reference. In such situations, an attenuation network is added to the neutral, thus forming a large resistance between neutral and ground. This 11-page Application Note analyzes the performance impact of adding a neutral attenuation network in a 3P4W wye system.
The ADE7912/ADE7913 3-channel, isolated, Σ-Δ analog-to-digital converters (ADCs) target polyphase energy metering applications using shunt current sensors. This 11-page Application Note provides in depth explanations on how to use the ADE7912/ADE7913 when developing a direct, 3-phase meter with shunts.
Noise is extremely important to designers of high-performance analog circuits. This is especially true for high-speed clocks, analog-to-digital converters (ADCs), digital-to-analog converters (DACs), voltage-controlled oscillators (VCOs), and phase-locked loops (PLLs). The key to reducing the output voltage noise is keeping the ac closed-loop gain close to unity without compromising the ac performance and dc closed-loop gain. This 8-page Application Note describes how to use a simple RC network to reduce the output noise of an adjustable low dropout regulator (LDO). Experimental data for several LDOs is presented to demonstrate the efficacy of this simple circuit technique. Although noise reduction (NR) is the primary focus, test data also shows the effect on power supply rejection ratio (PSRR) and transient load response.
Current sense amplifiers are used in a variety of applications, such as motor or solenoid control, load current monitoring, and fault detection. In such applications, it is typical for the input common-mode voltage to swing from ground to a certain high-side supply. While a user may assume that the input common-mode swings are limited to this high-side supply, transient voltages must be considered. The result of these transients is that a supposed low-voltage application tends to appear as a high-voltage application, and the current sense amplifier must be robust enough to handle these occurrences. This 2-page Application Note explains how to choose a suitable amplifier.
The ADuCM360/ADuCM361 32-bit, Cortex™-M3-based microcontrollers integrate 24-bit Σ-Δ analog-to-digital converters (ADC), each with a fully programmable instrumentation amplifier front-end. These microcontrollers target a wide range of applications including industrial control and instrumentation. In many of the target applications, self-diagnostic features are important in safety critical environments for smart recovery from failure modes. This 6-page Application Note describes some of the features that diagnose issues with the ADuCM360/ADuCM361 and surrounding circuitry.
Heterodyne radios, such as the ADF7024 transceiver, use a mixer to downconvert received radio frequency (RF) signals to an intermediate frequency (IF). Interfering signals, called interferers, that lay on the image frequency are also mixed down to the wanted frequency. The interfering signals desensitize the receiver, resulting in blocking on the wanted channel. In theory, an ideal transceiver that employs an IQ receive architecture can be configured to prevent the image frequency from mixing onto the wanted channel. This assumes that the gain balance and the phase orthogonality of the mixer quadrature paths are perfectly aligned. In practice, some imbalance exists due to imperfections in the mixer. This 6-page Application Note describes the fully autonomous image rejection (IR) calibration firmware download module for the ADF7024 transceiver IC.
This 10-page Application Note describes anisotropic magnetoresistive (AMR) thin film materials, which are becoming increasingly important for position sensing. Magnetoresistive (MR) position measurement has many advantages over traditional technologies, including reliability, accuracy, and overall robustness. Low cost, small relative size, contactless operation, wide temperature range, insensitivity to dust and light, and operation over a wide magnetic field range all lead to a robust sensor design.
Power supply sequencing is required for microcontrollers, field programmable gate arrays (FPGAs), digital signal processors (DSPs), analog-to-digital converters (ADCs), and other devices that operate from multiple voltage rails. These applications typically require that the core and analog blocks be powered up before the digital input/output (I/O) rails, although some designs may require other sequences. Proper power-up and power-down sequencing can prevent both immediate damage from latch-up and long-term damage from electrostatic discharge (ESD). In addition, sequencing the supplies staggers the inrush current during power-up, an especially helpful technique in applications operating from current-limited supplies. This Application Note discusses the advantages and disadvantages of using discrete components to sequence the power supplies and describes a simple, yet effective, method of achieving sequencing by using the internal precision enable pins of the ADP5134, which combines two 1.2 A buck regulators with two 300 mA low dropout (LDO) regulators. It also describes sequencer ICs that may be useful for applications that require more accurate and flexible sequencing.
This Application Note describes how to apply the ADE7912/ADE7913 isolated sigma-delta ADCs to measure analog 4-mA to 20-mA current loops. Current loops implement a robust sensor standard, so many industrial process control applications still employ them for analog signaling. The signaling current flows through all components, with the same current flowing even if the terminations are less than perfect, and all loop components drop voltage due to the current flowing through them. The signaling current is not affected by these voltage drops as long as the supply voltage is greater than the sum of the drops around the loop at the maximum current.
This Application Note shows how to enable the new 4:2:0 feature on the ADV8005 video signal processor and ADV7625/ADV7626/ADV7627 HDMI transceivers. This feature allows receiving and transmitting ultra-HD video with a 60-Hz refresh rate (4k × 2k at 60 Hz) using a 3-GHz bandwidth. The newly introduced format reduces the chroma information for YCrCb, but increases the luma bandwidth. In the 4:2:0 format, two luma samples are sent for one chroma sample, reducing the number of video pixels sent per line.
The ADE7854A/ADE7858A/ADE7868A/ADE7878A are enhanced versions of the ADE7854/ADE7858/ADE7868/ ADE7878 energy measurement ICs. This Application Note describes the differences between these products and is recommended for use alongside the data sheet.
Applications such as bipolar amplifiers, optical modules, CCD bias, and OLED displays usually require a negative output voltage from a positive input voltage. Designers of power management systems need versatile switching controllers and regulators that allow them to solve these power management challenges. The ADP2441/ADP2442 switching regulators provide synchronous buck functionality, ranging from a 36 V input voltage down to 0.6 V output voltage at up to 1 A with a switching frequency range from 300 kHz to 1 MHz. Although targeted for synchronous step-down applications, their versatility allows them to realize an inverting buck boost topology, which can generate a negative output voltage from a positive input voltage, without additional cost, component count, or solution size. This Application Note describes how to implement a synchronous inverting buck boost topology to generate negative output voltages from positive input power supplies.
Configurable output ranges reduce the need for multiple product variants to support various range options. This circuit uses the AD5422 16-bit, serial input, unipolar/bipolar voltage and current output DAC to provide voltage output ranges of 0 V to 5 V, 0 V to 10 V, −5 V to +5 V, or −10 V to +10 V with a 10% overrange capability; a current output, accessed from a separate pin, can provide 4 mA to 20 mA, 0 mA to 20 mA, or 0 mA to 24 mA ranges. The current and voltage output pins can be connected together by adding a buffer amplifier or switch to prevent a current leakage path through an internal resistor when the device is in current output mode.
Current sense amplifiers are used to amplify small differential signals in the presence of large common-mode voltages, to measure the voltage across a shunt resistor, for example. Current sense amplifiers can operate with supply voltages as low as 1.8 V and withstand input common-mode voltages as high as 600 V. Many applications, including H-bridge motor drivers, solenoid controllers, and dc-to-dc switching converters, have common-mode voltages that vary as a function of time. An ideal current sense amplifier does not react to the input common-mode variation, but real current sense amplifiers have finite common-mode rejection, typically specified at about 100 μV/V (80 dB) at dc. This Application Note focuses on the common-mode step response of current sense amplifiers.
Blood analyzers, in-vitro diagnostic systems, and other chemical analysis applications require fluid transfer from one vessel to another. These systems must efficiently aspirate samples from cuvettes or reagents from bottles. Lab-based systems that process large numbers of samples must process them as quickly as possible. To minimize the impact of probe motion on processing time, the probes used for aspiration must move at high speed. Moving the probe efficiently requires accurate knowledge of the location of the probe in relation to the surface of the fluid being drawn. This Application Note demonstrates how a capacitance-to-digital converter (CDC) can be used to determine the probe location with a high level of confidence.
The evaluation board for the AD9129 14-bit, 5.6-GSPS RF digital-to-analog converter uses power supply filters to guarantee optimal performance. This 3-page Application Note explores the effects of removing most of the filter components. All ferrite beads on the board were removed, as well as the majority of the capacitors on the power supplies. Phase noise, noise spectral density (NSD), spurious-free dynamic range (SFDR), intermodulation distortion (IMD), and adjacent channel leakage ratio (ACLR) performance were all measured to demonstrate the effect of removing the filter components. The measurement results showed that the ferrite beads improved close-in phase noise at 20 Hz offset by approximately 5 dB, as well as single-tone IMD by up to 5 dB. Most of the capacitors proved to be redundant, however. The decoupling capacitors improved the ACLR for 6 MHz carriers by 5 dB; and the capacitor arrays improved the ACLR for 6 MHz carriers by approximately 6 dB and the NSD by approximately 1 dB. Removing all of the other the capacitors did not affect the performance.
This 4-page Application Note describes a protocol for programming the flash memory in the ADuMC320 precision analog microcontroller, which incorporates high performance analog and digital peripherals, an ARM Cortex-M3 processor, and flash memory. Its MDIO interface can operate at up to 4 MHz, simultaneously executing from one flash block and writing/erasing the other flash block.
This 8-page Application Note describes a reference design that improves the overall link budget by extending the range of the ADF7023 ISM band transceiver by almost 20 dB. In a non-interference-limited line-of-sight scenario, this equates to a range increase of approximately six to seven times. The design, which consists of an ADF7023 transceiver and an RFFM6901 front-end module, is suitable for operation in the 902 MHz to 928 MHz ISM band and complies with FCC regulations.
This 11-page Application Note specifies the EEPROM programming and calibration for the ADP1050 and ADP1051 digital controllers for isolated power supplies during power supply manufacturing. First, the hex file used for EEPROM programming is generated by the GUI software in the power supply development stage. Second, using the generated hex file, the EEPROM can be programmed. Finally, the calibration procedure is presented.
This 18-page Application Note answers a series of frequently asked questions about digital potentiometer (digiPOT) products. It includes general questions as well as specific questions, including product-specific questions. In addition, it provides digiPOT configuration information.
The ADIS16445 and ADIS16448 are low profile, fully calibrated, MEMS inertial measurement units (IMU). This 4-page Application Note provides mechanical guidelines for mounting the IMU package, which provides four mounting holes, with recessed mounting ledges that help manage the overall height of the attachment hardware. The mounting holes provide enough clearance for M2 × 0.4 mm or 2-56 machine screws.
The ADE7912 and ADE7913 isolated 3-channel, Σ-Δ ADCs target polyphase energy metering applications using shunt current sensors. The devices can be used to sense dc signals, however, so this 5-page Application Note presents their dc measurement performance. In energy metering applications, the current channel is used to sense the voltage across shunt current sensors and the voltage channels are used to measure voltages across resistor dividers. From a dc measurement perspective, this separation is not meaningful because every channel can be used to sense dc signals. This application note describes the performance when dc signals are applied at the inputs of the three Σ-Δ ADCs.
This 7-page Application Note describes using the AD5755 and other similar industrial DACs in applications that do not require the dynamic power control (DPC) feature. DPC operates by sensing the load on the current output pin and supplying only the power that is required. To achieve this, the DAC controls a dc-to-dc converter to step up a 5-V supply to between 7.4 V and 29.5 V. DPC is particularly useful in systems with wide load ranges, including a short-circuit to ground, where all power generated by the supply is dissipated on chip. In non-DPC systems, this results in higher IC and system temperatures. Low-power applications may not require dynamic power control. In these cases, the dc-to-dc converter can be excluded from the design, reducing the number of external components. This is useful for space-constrained applications that require four channels. Instead of using the dc-to-dc converter, an external PMOS can limit on-chip power dissipation, or the DAC can be powered directly, with all power dissipated on chip.
This Application Note details the cyclic redundancy code (CRC) used in the ADAS1000 electrocardiogram front end. Error detection enables the receiver of a message to determine whether the message has been corrupted. To do this, the ADAS1000 constructs a code—called a checksum—that is a function of the message and appends it to the message. The CRC algorithm treats the message as an enormous polynomial, dividing it by another fixed polynomial using modulo-2 arithmetic for the coefficients. The remainder from this division is the checksum. Upon receipt of the message, the receiver can perform the same division and compare the remainder with the checksum. This note describes how the checksum is calculated.
Packages for the ADIS16375, ADIS16480, ADIS16485, and ADIS16488 include four 2.4-mm mounting holes, an aluminum housing, and a 2-row, 24-pin, 1-mm pitch electrical interface connector. This 4-page Application Note provides tips for system-level installation.
This 7-page Application Note describes the Reed-Solomon firmware module, which contains both forward error correction and advanced encryption standard (AES) encryption, for the ADF7023 transceiver. Reed-Solomon encoding appends check symbols to the transmitted data. When received, these symbols detect the presence of errors and correct them in the received data. The firmware module is flexible, allowing the user to select values that enable correction of up to five error bytes within a packet. Encoded packets are resilient to burst and random errors; their coding gain improves link margin.
This 11-page Application Note describes the radio performance of the ADF7021-N transceiver when configured for operation according to the wireless meter-bus (WM-Bus) standard, focusing on key receiver parameters applicable to the 2.4 kbps and 4.8 kbps modes of operation. These parameters are packet error rate (PER) over power, sensitivity over carrier frequency error, blocking, and adjacent channel selectivity.
The ADV7850, the first complete audio/video front-end device developed by Analog Devices, targets the professional and consumer video markets. The device incorporates a frame checker block that employs cyclic redundancy checking (CRC). This 3-page Application Note outlines the background of the frame checker function and details how it is utilized.
ADI provides symbols and footprints for components in binary Xlator (.bxl) files that were created using the Ultra Librarian tool offered by Accelerated Designs, Inc. A free version of this tool is available on the Accelerated Designs website. Once the .bxl file is opened, the Ultra Librarian Reader allows the footprint and symbol to be exported to one of many CAD toolsets, including Cadence® Allegro® Allegro®OrCAD®, Accel15/PCAD 2xxx/Altium6, Mentor PADS®, PowerPCB, and Zuken, Inc., CADSTAR®. These toolsets cover 97% of CAD users.
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