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Mixed Signal/Analog

24-Bit, 16-Channel Delta-Sigma ADC Simplifies Front-End Signal Conditioning

22nd March 2007

ES Admin

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Linear Technology has introduced the LTC2498 16-channel delta-sigma analog-to-digital converter (ADC), featuring a front-end design that can directly digitize a wide range of sensors. The LTC2498's Easy Drive design results in zero average differential input current, allowing measurements of high impedance input sources without the use of an internal buffer. This patented sampling scheme simplifies the design of front-end signal conditioning circuits and allows the ADC to be driven directly from bridges, RTDs, thermocouples and other high impedance sensors. Rail-to-rail input signals can be directly digitized while maintaining excellent DC accuracy (2ppm INL).

The LTC2498 includes a high accuracy internal temperature sensor that offers 1/30°C resolution and 2°C absolute accuracy. The ADC converts the output of the temperature sensor or the input multiplexer, which can be configured for 16 single-ended channels, eight differential channels, or combinations of both. After a new channel is selected, the LTC2498's No Latency Delta-Sigma™ digital filter settles in a single cycle. The LTC2498 communicates via a 4-wire SPI-compatible serial interface and performs conversions at rates up to 7.5Hz or 15Hz while using the internal oscillator. The LTC2498 can be configured to reject line frequencies of 50Hz, 60Hz or simultaneous 50Hz/60Hz, while maintaining 600nVRMS noise across the full input voltage range.

For lower resolution applications, Linear Technology is also introducing the LTC2496, a pin-compatible 16-bit ADC. The LTC2498 and LTC2496 are each available in QFN-38 (5mm x 7mm) packages, offering a pin-compatible and code-compatible family for performance/cost optimization. Both Easy Drive delta-sigma ADCs are available in commercial and industrial temperature ranges. Pricing begins at $3.45 each for the LTC2498 and $2.65 each for the LTC2496, in 1,000-piece quantities.