Medical, industrial measurements targeted by single-channel A/D collection

January 30, 2014 // By Graham Prophet
Texas Instruments’ SAR (successive approximation register) analogue-to-digital converter (ADC) product portfolio gains 12 devices that provide widest analogue supply and common-mode voltage ranges and that come with six reference designs for industrial and medical applications

The 1-channel ADS8881 family includes ultra-low power 18- and 16-bit SAR ADCs with speed options ranging from 100 ksamples/sec to 1 Msamples/sec.

Features include;

Widest input common mode: most of the new ADCs provide an input common-mode range that is 20-times wider than other devices. This simplifies signal conditioning and enables system designers to more easily digitise the difference between two independent sensor signals with widely varying common-mode voltage values over time.

Flexible analogue and digital supply voltage ranges: analogue supply voltage range of 2.7 V to 3.6 V, three times wider than existing devices. This enables direct operation from a Lithium-Ion battery. Digital supply voltage range is 1.65 V to 3.6 V, meeting most microprocessor supply requirements.

Ultra-low power: The 1-MSPS SAR ADCs consume 5.5 mW of power at 1 Msamples/sec and 55 µW at 10 ksamples/sec, making them suitable for pulsed DC measurements in portable medical and heat-sensitive automated test applications.

All 12 devices are pin-compatible and available in both MSOP and QFN package options, to reuse the same analogue signal chain design.

The following TI Precision Designs reference design circuits provide theory, simulation, calculation, and design methodology;

Multiplexed and step-response:

Data Acquisition for MUX and Step Inputs, 18 bits, 1 µsec Full-Scale Response

16-bit, 400-ksamples/sec, 4-ch. Multiplexed Data Acquisition System for High-Voltage Inputs

High precision:

Data Acquisition Optimised for Lowest Distortion, Lowest Noise, 18 bit, 1Msamples/sec

Low power:

Data Acquisition at 1 kHz AC, 1 mW, 18 bit, 1 Msamples/sec

Data Acquisition for 10 kHz AC, 35mW, 18 bit, 1 Msamples/sec

Medical:

Data Acquisition Block for ECG Systems, Discrete LEAD/ECG Implementation

The ADS8881EVM-PDK, ADS8861EVM-PDK and ADS8860EVM-PDK performance development kits costUS$199. IBIS and TINA-TI™ models are also available.

The ADC8881 family is available in the following 10-pin, 3-mm by 4.9-mm MSOP and 3-mm by 3-mm QFN options:

Device

Resolution

Sample rate

Signal-to-noise ratio (SNR)

Signal-to-noise + distortion (SINAD)

Price (1,000 units)

ADS8881

18

1 MSPS

100