Convertor digitises multiple ratiometric sensors

Edited by the Electronicstalk editorial team Feb 10, 2005

The LTC2447 is a high accuracy, variable speed/resolution 24bit delta-sigma ADC that features a unique multiplexing architecture to directly digitise multiple ratiometric sensors.

New from Linear Technology, the LTC2447 is a high accuracy, variable speed/resolution 24bit delta-sigma ADC that features a unique multiplexing architecture to directly digitise multiple ratiometric sensors.

Four differential inputs, coupled with four differential reference inputs, allow ratiometric measurements of multiple RTDs, bridges and pressure sensors.

A fifth differential reference can be shared by any or all inputs.

This multiplexing architecture, combined with high accuracy and low drift, improve the performance while simplifying the analogue front end of applications measuring temperature, pressure, flow, chromatography, weight, and general purpose data acquisition.

The LTC2447's flexible input multiplexer allows any combination of eight single-ended or four differential inputs to be accurately digitised with either a dedicated reference input or a global reference input.

The LTC2447's multiplexer outputs and ADC inputs are pinned out separately.

This allows external signal chain components to be included within the calibration loop of the ADC, automatically removing offset and drift errors.

The fast 4kHz multiplexing rate combined with the patented No Latency Delta-Sigma architecture allows all eight channels to be scanned in 2ms, without the filter settling problems inherent in other delta-sigma convertors.

The LTC2447's programmable filter enables designers to tailor 20 different speed/resolution combinations to individual channels.

For low output rate applications, the ADC provides 200nV RMS noise, which is equivalent to 500,000 counts on a +/-50mV sensor output (or 25 million counts on a full scale input) and simultaneous 50 and 60Hz line frequency noise rejection.

At its fastest output rate, 8kHz, the ADC provides over 17 effective bits.

For applications not requiring the signal chain calibration feature, the pin-compatible LTC2446 is available.

The LTC2446 and LTC2447 are offered in 38-pin 5 x 7mm QFN packages, screened for industrial and commercial temperature ranges.

Pricing starts at $7.15 each in 1000-piece quantities.