TIDA-01214

Isolated, High-Accuracy Analog Input Module Reference Design Using 16-Bit ADC and Digital Isolator

TIDA-01214

Design files

Overview

This reference design provides accurate measurements of AC voltage and current inputs using a precision 16-bit SAR ADC over a wide input range, covering protection and measurement range (including sampling requirements of IEC 61850-9-2), simplifying system design and improving trip time performance and reliability. The analog input module (AIM) is isolated from the host processor using a digital isolator with an integrated power. For a limited function and cost optimized  design approach, An AC AIM can be designed using only three TI products, reducing system cost and board size. The alarm feature identifies the AC analog input faults on a sample basis for faster fault detection. The ADC has an additional auxiliary channel to diagnose the supply output of the digital isolator. A 12-bit ADS8668 ADC with a gain amplifier can increase the dynamic range by using programmable internal ranges, further optimizing the system cost.

Features
  • This reference design is based on ADS8688A 16-bit SAR ADC and supports measurement of up to 16 analog inputs by daisy chaining
  • ADC interface isolated from host for improved safety in harsh operating conditions using ISOW7841 with integrated power converter providing current output of > 60 mA with efficiency ≥ 45%
  • AC AIM provides ENOB of > 14.9 bits, SNR of > 91 dB, and THD of > –110 dB
  • 12-bit ADC8668 with front-end gain amplifier for increasing dynamic range of low-voltage output sensors in cost-optimized applications
  • Load switch used at input of ISOW7841 to protect AC AIM during output overload

A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products

Design files

Download ready-to-use system files to speed your design process.

TIDUD64A.PDF (929 K)

Reference design overview and verified performance test data

TIDRSJ3.ZIP (1254 K)

Detailed schematic diagram for design layout and components

TIDRSJ4.ZIP (520 K)

Complete listing of design components, reference designators, and manufacturers/part numbers

TIDRSJ5.ZIP (716 K)

Detailed overview of design layout for component placement

TIDRSJ7.ZIP (7943 K)

Files used for 3D models or 2D drawings of IC components

TIDCDT0.ZIP (2975 K)

Design file that contains information on physical board layer of design PCB

TIDRSJ6.ZIP (4008 K)

PCB layer plot file used for generating PCB design layout

Products

Includes TI products in the design and potential alternatives.

Analog temperature sensors

LMT700.1C analog temperature sensor, -5.19 mV/C, high-precision matched pairs, output enable pin

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Boost converters (integrated switch)

LM50013.1-75V Wide Vin, 1A Current Mode Non-Synchronous Switch Mode Regulator

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Boost converters (integrated switch)

TPS6104028-V, 400-mA Switch Boost Converter in SOT-23 for LCD and White LED Applications

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Charge pumps (inductorless)

LM27762Low-Noise Positive- and Negative-Output Charge Pump With Integrated LDO

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Charge pumps (inductorless)

REG7105560-mA, 5.5V, Buck/boost Charge Pump in ThinSOT-23

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Charge pumps (inductorless)

TPS60241170 uVrms Zero-Ripple Switched Cap Boost Converter With Fixed 5.0V Output For VCO Supply

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Charge pumps (inductorless)

TPS6040360mA Charge Pump Voltage Inverter with Fixed 250kHz Operation

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Comparators

TLV3012Low-power comparator with reference (push-pull)

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Digital isolators

ISO7741Robust EMC, quad-channel, 3/1, reinforced digital isolator

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Digital isolators

ISO7841Highest isolation rating, quad-channel, 3/1, reinforced digital isolator

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General-purpose op amps

OPA322Single, 5.5-V, 20-MHz, 65-mA output current, low noise (8.5-nV/√Hz) operational amplifier

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Instrumentation amplifiers

INA333Low-Power, Zero-Drift, Precision Instrumentation Amplifier

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Linear & low-dropout (LDO) regulators

TPS717150-mA, high-PSRR, low-IQ, low-dropout voltage regulator with enable

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Linear & low-dropout (LDO) regulators

TPS723200-mA, negative, adjustable low-dropout voltage regulator with enable

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Linear & low-dropout (LDO) regulators

TPS791100-mA, low-noise, low-dropout voltage regulator with enable

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Linear & low-dropout (LDO) regulators

TPS7A49150-mA, 36-V, low-noise, high-PSRR, adjustable low-dropout voltage regulator with enable

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Load switches

TPS229445.5-V, 0.1-A, 500-mΩ, load switch with current limit and active high enable

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N-channel MOSFETs

CSD17571Q230-V, N channel NexFET™ power MOSFET, single SON 2 mm x 2 mm, 29 mOhm

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Noninverting buffers & drivers

SN74LVC1G17Single 1.65-V to 5.5-V buffer with Schmitt-Trigger inputs

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Precision ADCs (<=10MSPS)

ADS866812-Bit 500kSPS 8-Channel SAR ADC With Bipolar Inputs Off 5V Supply

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Precision ADCs (<=10MSPS)

ADS867814-Bit 500kSPS 8-Channel SAR ADC With Bipolar Inputs Off 5V Supply

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Precision ADCs (<=10MSPS)

ADS868816-bit, 500-kSPS, 8-channel, single-supply SAR ADC with bipolar input ranges

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Precision ADCs (<=10MSPS)

ADS8688A16-bit, 500-kSPS, 8-channel SAR ADC with bipolar inputs using 5-V supply and low-drift VREF

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Precision ADCs (<=10MSPS)

ADS869818-Bit 500kSPS 8-Channel SAR ADC With Bipolar Inputs Off 5V Supply

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Precision op amps (Vos<1mV)

OPA320Precision, zero-crossover, 20-MHz, 0.9-pA Ib, RRIO, CMOS operational amplifier

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Precision op amps (Vos<1mV)

OPA376Precision (0.025mV), low noise (7.5nV/rtHz), low quiescent current (760uA) op amp

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Precision op amps (Vos<1mV)

OPA41800.1 uV/C Drift, Quad, Low Noise, Rail-to-Rail, 36V Zero Drift Op Amp

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Series voltage references

REF50404.096-V, 3-µVpp/V noise, 3-ppm/°C drift precision series voltage reference

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Series voltage references

REF60414.096-V, 5-ppm/°C high-precision voltage reference with integrated buffer & enable pin

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Signal isolators with integrated power

ISOW7841Quad-channel, 3/1, reinforced digital isolator with integrated power

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Supervisor & reset ICs

TPS3808Low-quiescent current supervisor with programmable delay & manual reset

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Supervisor & reset ICs

TPS3836Active-low, push-pull, nano-power supervisors with manual reset

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Transformer drivers

SN6505BLow-noise, 1-A, 420-kHz transformer driver with soft start for isolated power supplies

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Technical documentation

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* Design guide Isolated, High-Accuracy Analog Input Module Reference Design Using 16-Bit ADC (Rev. A) Aug. 17, 2018

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