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Engineer-to-Engineer and Application Notes

These engineer-to-engineer and application notes, published within the past 12 months, are listed in chronological order.

July 2015

AN-1349: PCB Implementation Guidelines to Minimize Radiated Emissions on the ADM2582E/ADM2587E RS-485/RS-422 Transceivers

This application note examines specific layout options and component selection to achieve radiated emissions standards EN55022/CISPR22 Class A (FCC Class A) emissions standards commonly used in industrial environments, and EN55022/CISPR22 Class B (FCC Class B) standards in an unshielded environment, for the ADM2582E/ADM2587E RS-485/RS-422 transceivers.

AN-1364 Differential Filter Design for a Receive Chain in Communication Systems

This application note looks at some basic filter key specifications concepts, a few types of frequently used filter responses, a Chebyshev Type 1 filter application, and step-by-step instructions on how to transfer a single-ended filter design to a differential filter design. A differential filter design example is in this application note as well as a few points on how to optimize differential circuit PCB design.

June 2015

AN1352: Calibration Procedures for the ADA4571

The ADA4571 is an analog anisotropic magnetoresistive (AMR) angle sensor consisting of a sensing element and a conditioning analog instrumentation amplifier. This application note discusses various simple calibration procedures to reduce the angle linearity error from the device.

April 2015

AN-1340: ADF7023-J IEEE 802.15.4g/UBUSAir/FAN Firmware Module

This application note describes the IEEE 802.15.4g (15d4g) firmware download module for the ADF7023-J transceiver IC. The firmware module adds the following features: IEEE 802.15.4g physical layer header formatting and data whitening, transmitter/receiver rolling data buffer, 4‑byte to 1000-byte preamble, and ARIB STD T108 compliant clear channel assessment. The ADF7023-J low power, 902 MHz to 958 MHz transceiver contains a custom microcontroller core with mask ROM that implements packet handling functions and translates radio commands into internal control sequences. An additional 2 kB of program RAM is available and serves as program code memory, which enables the radio controller commands that provide modified or extended functionality. The IEEE 802.15.4g firmware download module described in this application note is based on program code downloaded into the program RAM.

March 2015

AN-1339: ADF7023-J AD_15d4g Firmware Download Module

This application note describes the AD_15d4g firmware download module for the ADF7023-J transceiver IC. This firmware download module adds the following features to the ADF7023-J: IEEE 802.15.4g physical layer (PHY) header formatting, IEEE 802.15.4g data whitening, Tx/Rx rolling data buffer, 1 byte to 1000 byte Tx preamble, ARIB STD T108 clear channel assessment (CCA), and Rx antenna diversity.

AN-1318: Differential Overvoltage Protection Circuits for Current Sense Amplifiers

Most current sense amplifiers are capable of handling high common-mode voltages (CMVs) but not high differential input voltages. In certain applications, there are fault conditions wherein the differential input voltage at the shunt exceeds the specified maximum voltage of the amplifier. These conditions can cause damage to the amplifier. This application note introduces two basic overvoltage protection circuits for current sense amplifiers and discusses the effects of the circuits on device performance for two types of current sense architectures—a current sense amplifier (using the AD8210 as an example) and a difference amplifier (using the AD8418 as an example).

January 2015

AN-1347: Operating the ADF4360-7 at High PFD Frequencies

The ADF4360-7 is a very flexible synthesizer (phase-locked loop (PLL) with an integrated voltage controlled oscillator (VCO)) that enables the generation of frequencies from 350 MHz to 1800 MHz. An on-chip calibration engine fine tunes the output frequency after power-on. Under most operating conditions, the calibration process works well; however, timing uncertainty errors can occur, which result in tuning errors that degrade the phase noise and/or spurious performance. This application note describes how to maintain optimum performance when operating the device at a relatively high phase frequency detector (PFD) frequency.AN-1337

AN-1343: Energy Metering on Hot Swap and Power Monitor Devices

A variety of hot swap and power monitor devices, including the ADM1075, ADM1276, ADM1278, ADM1293, and ADM1294 include energy metering functionality. Each device can measure input voltage as well as output current. The 12-bit input voltage and 12-bit output current measurement values are multiplied to give the input power value. This multiplication uses fixed point arithmetic and produces a 24-bit value. The PMBus™ Application Profile for Hot Swap Controllers specifies that users can read individual power samples or use on-chip energy metering functionality. The advantage of on-chip functionality is that the host processor does not have to poll the power monitor continuously to read power samples. Individual power samples are accumulated on chip, so the user can read from the power monitor via PMBus intermittently, freeing up the I2C bus for other transactions.

AN-1342: AD9142 to AD9142A Migration

The AD9142 and AD9142A dual 16-bit high-speed digital-to-analog converters (DACs) use low-voltage differential signaling (LVDS). The AD9142A, recommended for new designs, serves wider bandwidth applications due to its higher maximum interface speed. This application note describes the differences between the two products and provides a guide for upgrading from the AD9142 to the AD9142A.

AN-1341: Using the AD8436 True RMS to DC Converter

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.

AN-1335: Temperature Measurements on the ADE7932/ADE7933 and ADE7978 Chipset

The ADE7932/ADE7933 and the ADE7978 form a chipset for measuring 3-phase electrical energy measurement using shunts as current sensors. The ADE7932 and ADE7933 contain a temperature sensor that is measured by the ADE7978. The temperature is used to compensate the gain variation in the current channel datapath. This application note presents the factors that influence the meter performance over temperature, and how temperature measurements are used to compensate these factors and make the meter more stable with temperature.

December 2014

AN-1338: ADM1278 Design Guide

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.

AN-1322: ADuCM320 Code Execution Speed

The ADuCM320 contains an ARM® Cortex®-M3 processor with integrated flash and RAM for code and data. To increase the execution speed of the central processing unit, it also includes a cache with various modes of operation. This application note presents the modes that are of interest for user applications, without covering the specific features of the ARM Cortex-M3.

AN-1319: Compensator Design for a Battery Charge/Discharge Unit Using the AD8450 or the AD8451

Most battery formation and test systems implement the CC-CV algorithm using high-accuracy feedback loops that control the battery current and voltage. To ensure high battery quality, the feedback loops need to be stable and robust. This 20-page Application Note describes how to design and implement the compensation network for the constant current and constant voltage feedback loops in a battery test or formation system using the AD8450 or AD8451 analog front-end and controller.

November 2014

AN-1336: Adaptive Dead Time in Full Bridge Phase Shifted Topology Using ADP1055

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.

AN-1333: Architecting a Direct, 3-Phase Energy Meter with Shunts Using the ADE7932/ADE7933/ADE7978

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.

AN-1317: Rolling Data Buffer on the ADF7024

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.

October 2014

AN-1334: Impact of Adding a Neutral Attenuation Network in a 3P4W Wye System

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.

AN-1332: Architecting a Direct, 3-Phase Energy Meter with Shunts Using the ADE7912/ADE7913

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.

AN-1329: Noise Reduction Network for Adjustable Low Dropout Regulators

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.

AN-1321: Common-Mode Transients in Current Sense Applications

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.

AN-1320: ADuCM360/ADuCM361 Self Diagnostic Features

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.

AN-1315: Autonomous IR Calibration on the ADF7024

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.

AN-1314: AMR Angle Sensors

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.

August 2014

AN-1311: Complex Power Supply Sequencing Made Easy

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.

July 2014

AN-1312: Applying the ADE7912/ADE7913 to 4 mA to 20 mA DC Measurements

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.

AN-1299: Enabling HDMI 2.0 Using ADV8005 and ADV7625/ADV7626/ADV7627

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.

AN-1272: Differences Between the ADE7854A/ADE7858A/ADE7868A/ADE7878A and ADE7854/ADE7858/ADE7868/ADE7878 Products

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.

AN-1269: Designing an Inverting Power Supply Using the ADP2441/ADP2442 Synchronous Step-Down DC-to-DC Regulators

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.

June 2014

AN-1313: Configuring the AD5422 to Combine Output Current and Output Voltage to a Single Output Pin

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.

AN-1308: Common-Mode Step Response of Current Sense Amplifiers

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.

AN-1301: Using CDCs to Control Motion for Sample Aspiration

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.

AN-1296: Optimizing Power Supplies for the AD9129

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.


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