Increasing measurement rates while keeping low power consumption poses challenges

Analogue, Mixed Signal, LSI

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15 August 2001 Analogue, Mixed Signal, LSI

Smart transmitter designers are challenged to increase measurement rates of prime variable and secondary variables yet also keep power consumption under control.

In modern smart transmitters or field instruments there is ever-present pressure to increase the measurement or throughput rate of the prime variable. This increase in throughput allows software algorithms like PID loops to be executed in a shorter time for tighter system control. At the same time there is also a requirement to measure other, secondary variables, inside the smart transmitter. Secondary variables like temperature, voltage, excitation currents, etc can generally be measured at slower rates but they still consume precious A/D converter time. Analog Devices has introduced a new ADC configured to sample simultaneous inputs that can help solve this dilemma.

The company's AD7719 ADC contains two modulators on a single piece of silicon. The main channel comprises a 24 bit, no-missing-code A/D converter, with an input PGA and multiplexer. The analog input channels can be programmed to behave as either one or two differential channels, or as three pseudo-differential inputs with respect to a common pin. A rail-to-rail high-impedance input buffer allows buffered operation to 100 mV of either supply rail.

The chip's secondary channel comprises a 16 bit ADC with input multiplexer and choice of two single-ended inputs or one differential input. Both ADCs have separate reference inputs. The main channel can continuously convert the prime variable while the secondary channel can simultaneously convert the secondary variables. Thus, the AD7719 solution can ensure maximum throughput rate for the prime variable, while easily and accurately accommodating secondary variables.

It operates from single 2,7 V to 5,25 V supply and comes in 28-lead SOIC and TSSOP packages.

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Increasing measurement rates while keeping low power consumption poses challenges

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