Integrated 24-bit ADC, analogue front-ends blend low power, low noise

July 28, 2015 // By Graham Prophet
Two analogue front-end (AFE) devices with integrated 24-bit sigma-delta converter cores deliver, claims Analog Devices, the best-available combination of low-power, low-noise and signal chain integration.

AD7124-4 and AD7124-8 AFEs connect directly to all standard industrial signal sources and sensor inputs, while reducing power requirements by 40% over comparable devices. The power performance suits the new AFEs for an array of industrial and instrumentation applications including low power portable equipment. The high degree of integration of the AD7124-4 (four differential and seven pseudo-differential inputs) and the AD7124-8 AFE (eight differential and 15 pseudo-differential inputs) simplifies design architecture and shortens the design cycle by providing the flexibility to support easily multiple types of sensor inputs, including resistance temperature detectors, thermocouples, voltage/current inputs and current bridges. Enabling the highest system channel density of any comparable products, these AFEs allow designers to reduce PCB footprint or apply the space savings to expand monitoring and connectivity functions within the same board area.

The devices incorporate a fully integrated signal chain with a 24-bit sigma-delta A/D converter, programmable gain amplifier (PGA), precision reference, reference buffers, current sources, temperature sensor and excitation sources on a single chip. Integrated diagnostic features support SIL compatibility and reduce the need for discrete diagnostic components saving valuable PCB area.

AD7124-4 and AD7124-8 offer three user-selectable power modes that allow system designers to optimise throughput rate versus required noise performance. In the lowest power mode (255 µA) the converter delivers 21.7 noise free bits at low sampling rates. The user-selectable power modes allow designers of programmable-logic controllers, process controllers, transmission systems and other industrial and instrumentation equipment to develop a single platform by precisely matching power/performance requirements for each use case.

Analog Devices; www.analog.com/en/products/analog-to-digital-converters/precision-adc-10msps/ad7124-4 and www.analog.com/en/products/analog-to-digital-converters/precision-adc-10msps/ad7124-8

next page; feature summary...