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LTC2449 - 24-Bit High Speed 8-/16-Channel Delta Sigma ADCs with Selectable Speed/Resolution

The LTC2444/LTC2445/LTC2448/LTC2449 are 8-/16- channel (4-/8-differential) high speed 24-bit No Latency Delta Sigma ADCs. They use a proprietary delta-sigma architecture enabling variable speed/resolution. Through a simple 4-wire serial interface, ten speed/resolution combinations 6.9Hz/280nVRMS to 3.5kHz/25µVRMS (4kHz with external oscillator) can be selected with no latency between conversion results or shift in DC accuracy (offset, full-scale, linearity, drift). Additionally, a 2X speed mode can be selected enabling output rates up to 7kHz (8kHz if an external oscillator is used) with one cycle latency.

Any combination of single-ended or differential inputs can be selected with a common mode input range from ground to VCC, independent of VREF. While operating in the 1X speed mode the first conversion following a new speed, resolution, or channel selection is valid. Since there is no settling time between conversions, all 8 differential channels can be scanned at a rate of 500Hz. At the conclusion of each conversion, the converter is internally reset eliminating any memory effects between successive conversions and assuring stability of the high order delta-sigma modulator.

Features Up to 8 Differential or 16 Single-Ended Input Channels Up to 8kHz Output Rate Up to 4kHz Multiplexing Rate Selectable Speed/Resolution 2µVRMS Noise at 1.76kHz Output Rate 200nVRMS Noise at 13.8Hz Output Rate with Simultaneous 50/60Hz Rejection Guaranteed Modulator Stability and Lock-Up Immunity for any Input and Reference Conditions 0.0005% INL, No Missing Codes Autosleep Enables 20µA Operation at 6.9Hz <5µV Offset (4.5V < VCC < 5.5V, –40°C to 85°C) Differential Input and Differential Reference with GND to VCC Common Mode Range No Latency Mode, Each Conversion is Accurate Even After a New Channel is Selected Internal Oscillator-No External Components LTC2445/LTC2449 Include MUXOUT/ADCIN for External Buffering or Gain Tiny QFN 5mm x 7mm Package Typical Application

Applications High Speed Multiplexing Weight Scales Auto Ranging 6-Digit DVMs Direct Temperature Measurement High Speed Data Acquisition Packaging

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