Analog Electronics I: Precision Measurement
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The element14 ESSENTIALS of Precision Measurement discusses the key parameters, characteristics, and applications of precision measurement analog ICs. To extend the knowledge covered in the main module, this supplementary guide discusses the types of related components and evaluation boards that can be used for products or prototyping.
Analog to Digital Converters
The MAX11410 is a low-power, multi-channel, 24-bit delta-sigma ADC with features and specifications that are optimized for precision sensor measurement. The input section includes a low-noise programmable gain amplifier (PGA) with very high input impedance and available gains from 1x to 128x to optimize the overall dynamic range. Input buffers provide isolation of the signal inputs from the switched-capacitor sampling network when the PGA is not in use, making the ADC easy to drive even with high-impedance sources. The 10-channel input multiplexer provides the flexibility needed for complex, multi-sensor measurements. GPIOs reduce isolation components and ease control of switches or other circuitry. When used in single-cycle mode, the digital filter settles within a single conversion cycle. The available FIR digital filter allows single-cycle settling in 16ms while providing more than 90dB simultaneous rejection of 50Hz and 60Hz line noise. The integrated on-chip oscillator requires no external components. If needed, an external clock source may be used instead.
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The MAX11168 is a 16-bit, 500ksps, SAR ADC offering excellent AC and DC performance with true bipolar input range, internal reference, and small size. The MAX11168 measures a ±5V (10VP-P) input range while operating from a single 5V supply. A patented charge-pump architecture allows direct sampling of high-impedance sources. It integrates a low drift reference with internal buffer, saving the cost and space of an external reference. This ADC achieves 92.3dB SNR and -101dB THD. The MAX11168 guarantees 16-bit no-missing codes and ±0.75 LSB INL (typ). The MAX11168 communicates using an SPI-compatible serial interface at 2.5V, 3V, 3.3V, or 5V logic. The serial interface can be used to daisy-chain multiple ADCs for multichannel applications and provides a busy indicator option for simplified system synchronization and timing.
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Digital to Analog Converters
The MAX5541 serial-input, voltage-output, 16-bit monotonic digital-to-analog converter (DAC) operates from a single +5V supply. The DAC output is unbuffered, resulting in a low 0.3mA supply current and low 1LSB offset error. The DAC output range is 0V to VREF. The DAC latch accepts a 16-bit serial word. A power-on reset (POR) circuit clears the DAC output to 0V (unipolar mode) when power is initially applied. The 10MHz 3-wire serial interface is SPI
/QSPI/ MICROWIRE-compatible and interfaces directly with optocouplers for applications requiring isolation. The MAX5541 is available in an 8-pin SO package.
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The MAX5715BOB (Break Out Board) provides for rapid prototyping and development with the MAX5715 (a 12-bit, 4-channel, voltage-output DAC). MAX5715BOB interfaces to any Arduino-compatible or mbed.org compatible platform with expansion ports configurable for SPI communication. Additionally, the MAX5715BOB works with systems that have a Pmod connection, a 2 x 6 right angle header at board edge (compatible Pmod interface spec) interface type 2A (expanded SPI) on 2x6 header at board edge. MAX5715BOB also comes with schematics, design files and firmware for immediate use or future projects.
Voltage References
The MAX6173AASA+ is a high precision voltage reference with temperature sensor in an 8-pin NSOIC package. It features a temperature coefficient curvature correction circuit and laser trimmed thin film resistors that result in a very low ±1.5ppm/°C temperature coefficient and excellent 0.06% initial accuracy. The MAX6173AASA+ provides a TEMP output where the output voltage is proportional to the die temperature making the device suitable for a wide variety of temperature sensing applications. It also provides a TRIM input allowing fine trimming of the output voltage with a resistive divider network. The low temperature drift and low noise makes this device ideal for use with high resolution ADC or DACs. It uses bandgap technology for low noise performance and excellent accuracy. It does not require an output bypass capacitor for stability and is stable with capacitive loads up to 100µF.
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The MAX6279 evaluation kit provides a proven design to evaluate the MAX6279 ceramic shunt voltage reference. The output voltage is set at 1.2V. The EV kit comes installed with a MAX6279ELA12+ in 8-pin ceramic leadless chip carrier (LCC) package. The MAX6279 EV kit demonstrates the MAX6279, a precision, two-terminal shunt mode, bandgap voltage reference in a small 8-pin LCC package. The EV kit requires a source greater than 1.225V at the VS test point and an operating current between 60µA and 15mA.
Audio Amplifiers
The MAX98357A/MAX98357B is a digital pulse-code modulation (PCM) input Class D amplifier that provides Class AB audio performance with Class D efficiency. The digital audio interface automatically recognizes up to 35 different PCM and TDM clocking schemes which eliminates the need for I2C programming. Operation is further simplified by eliminating the need for an external MCLK signal that typically used for PCM communication. Simply supply power, LRCLK, BCLK, and digital audio to generate audio! Furthermore, a novel pinout allows customers to use the cost-effective WLP package with no need for expensive vias The digital audio interface is highly flexible with the MAX98357A supporting I2S data and the MAX98357B supporting left-justified data. Both ICs support 8 channel time division multiplexed (TDM) data. The digital audio interface accepts specified sample rates between 8kHz and 96kHz for all supported data formats. The ICs can be configured to produce a left channel, right channel, or (left/2 + right/2) output from the stereo input data. The ICs operate using 16/24/32-bit data for I2S and left-justified modes as well as 16-bit or 32-bit data using TDM mode. The ICs eliminate the need for the external MCLK signal that is typically used for PCM communication. This reduces EMI and possible board coupling issues in addition to reducing the size and pin count of the ICs. The ICs also feature a very high wideband jitter tolerance (12ns typ) on BCLK and LRCLK to provide robust operation. Active emissions-limiting, edge-rate limiting, and overshoot control circuitry greatly reduce EMI.
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The MAX98390 evaluation system evaluates the MAX98390 boosted Class D audio amplifier with integrated Dynamic Speaker Management (DSM) IC. DSM senses the voltage and current at the load and uses patented Maxim algorithms to unlock the full potential of the speaker. The EV system comprises the MAX98390 Development Board (DEV board), Maxim's Audio Interface Board III (AUDINT3), 5V power supply, reference microspeaker, USB cable, DSM Sound Studio software, and MAX98390 evaluation software. It is recommended that the DEV board be evaluated with the AUDINT3 board as an EV system. MAX98390 supports standard I2S, left-justified, and TDM digital audio interfaces, as well as I2C for control. The AUDINT3 board provides 1.8V DVDD, USB-to-PCM, and USB-to-I2C interfaces that are needed to evaluate the DEV board, requiring only a single external power supply for VBAT.. The easy-to-use DSM Sound Studio software is a simple, yet powerful GUI that breaks down the DSM design process into three basic steps: extract, tune, and evaluate. Additionally, DSM Sound Studio provides for a 7-minute quick demo to hear the DSM difference using the included reference microspeaker.
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Op Amps
The MAX40100EVKIT# is an evaluation kit for the MAX40100 operational amplifier. It provides a proven design to evaluate the MAX40100 precision, low noise, low drift dual operational amplifier in a 6-bump wafer level package (WLP). It is preconfigured as non-inverting amplifiers, but can be adapted to other topologies by changing a few components. This EV kit has a preinstalled MAX40100AWT+ IC. Typical applications include battery powered devices, cell phones, loop powered systems, portable medical devices and sensor interfaces.
The MAX44246 is a 36V, ultraprecision, low-noise, low-drift, single/quad/dual operational amplifiers that offer near-zero DC offset and drift through the use of patented chopper stabilized and auto-zeroing techniques. This method constantly measures and compensates the input offset, eliminating drift over time and temperature and the effect of 1/f noise. These single/quad/dual devices feature rail-to-rail outputs, operate from a single 2.7V to 36V supply or dual ±1.35V to ±18V supplies, and consume only 0.42mA per channel, with only 9nV/√Hz input-referred voltage noise. The ICs are available in 8-pin FMAXM or SO packages and are rated over the -40NC to +125NC temperature range.
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Current-Sense Amplifiers
The MAX44284FAUT+T is a 36V, input common-mode, high precision, low power current-sense amplifier in 6 pin SOT-23 package. It is a high-side, current-sense amplifier that operates with a 1.7V to 5.5V single supply and is optimized for very low power operation with only 21µA of quiescent current. The MAX44284 is ideal for many battery-powered, handheld devices because it uses only maximum 31.2µA quiescent supply current to extend battery life. The device's low input offset voltage, tight gain error and low temperature drift characteristics allow the use of small-sense resistors for current measurements to improve power-supply conversion efficiency and accuracy of measurements.
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The MAX40201 dual-channel, high-side, current-sense amplifier has VOS of less than 12µV (max) and gain error of less than 0.1% (max). The outputs of the MAX40201 are voltage outputs capable of swinging to a few tens of millivolts of the VDD rail and ground. The MAX40201 features an input common-mode voltage range from 0V to 76V with 80kHz of small-signal bandwidth, which makes it ideal for interfacing with a SAR ADC for multichannel multiplexed data acquisition systems. The MAX40201 operates over the -40°C to +125°C temperature range. The MAX40201 is offered in 8-bump wafer-level package (WLP) and 8-pin µMAX
package.
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