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High-voltage SAR ADCs boost system accuracy in industrial applications

High-voltage SAR ADCs boost system accuracy in industrial applications

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By eeNews Europe



The eight-channel ADS8688 and four-channel ADS8684 allow input ranges up to ±10.24 V to be powered by a single 5-V supply, simplifying system power requirements. They claim the industry’s lowest gain drift, offset voltage and offset drift, and the highest precision reference, increasing levels of accuracy throughout the full extended industrial temperature range.

These ADCs can improve total system accuracy in a broad range of multi-channel industrial applications, including power automation, low- and medium-voltage relay protection, protection relay monitoring, factory automation equipment and programmable logic controllers (PLCs).

The ADS8688 family does not need high-voltage supplies; they support bipolar input ranges up to ±10.24 V and unipolar ranges up to ±10.24 V with a single 5-V supply. DC error performance: the parts achieve better than 99.9% accuracy without calibration with DC error specifications that boost system-level performance. With specified gain drift of 4 ppm/C and offset drift of 3 ppm/C, the devices eliminate the need for designers to spend time calibrating their systems over temperature ranges. An integrated precision reference and reference buffer improve low-temperature drift specifications, enabling precision performance without requiring external circuitry across the full extended industrial temperature range of minus 40C to 125C.

Each device integrates into one chip 20 active devices, including programmable gain amplifiers (PGAs), driver amplifiers, multiplexer, voltage reference, reference buffer and SAR ADC, plus an auxiliary channel input for interfacing straight to the ADC. This integration allows the ADS8688 and ADS8684 to connect directly to various sensor types that require no signal conditioning.

Tools and support include simulation models, hardware evaluation kits and reference designs: designers can evaluate the ADS8688 and ADS8684 in a fraction of the time they might spend, TI says, in evaluating other precision ADCs by using a new performance demonstration kit (PDK) that features a simple installation process. The PDK includes an evaluation module (EVM) and capture card for plug-and-play functionality, replacing online software installations with a one-click process. The kit’s GUI enables designers to quickly evaluate ADC performance in specific end equipment.

The following TI Designs reference designs provide theory, simulation, calculation, and design methodology:

Phase-compensated, eight-channel multiplexed data acquisition system for power automation (TIPD167).

16-bit, eight-channel integrated analog input module for PLCs (TIDA_00164).

The ADS8688 family of devices come in a 38-pin, 9.7-mm by 4.4-mm TSSOP package. The following 16-bit products are available, with 12- and 14-bit versions coming in 2015:

Device

Resolution

Speed

Channel count

Price

(1,000-unit)

ADS8688

16

500 kSPS

8

$US11.00

ADS8684

16

500 kSPS

4

$US8.00

Texas Instruments; www.ti.com/ADS8688-pr-eu

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