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LTC2440 - 24-Bit High Speed Differential Delta Sigma ADC with Selectable Speed/Resolution

The LTC2440 is a high speed 24-bit No Latency Delta Sigma ADC with 5ppm INL and 5µV offset. It uses proprietary Delta Sigma architecture enabling variable speed and resolution with no latency. Ten speed/resolution combinations (6.9Hz/ 200nVRMS to 3.5kHz/25µVRMS) are programmed through a simple serial interface. Alternatively, by tying a single pin HIGH or LOW, a fast (880Hz/2µVRMS) or ultralow noise (6.9Hz, 200nVRMS, 50/60Hz rejection) speed/resolution combination can be easily selected. The accuracy (offset, full-scale, linearity, drift) and power dissipation are independent of the speed selected. Since there is no latency, a speed/resolution change may be made between conversions with no degradation in performance.

Following each conversion cycle, the LTC2440 automatically enters a low power sleep state. Power dissipation may be reduced by increasing the duration of this sleep state. For example, running at the 3.5kHz conversion speed but reading data at a 100Hz rate draws 240µA average current (1.1mW) while reading data at a 7Hz output rate draws only 25µA (125µW).The LTC2440 communicates through a flexible 3-wire or 4-wire digital interface that is compatible with the LTC2410 and is available in a narrow 16-lead SSOP package.

Features Up to 3.5kHz Output Rate Selectable Speed/Resolution 2µVRMS Noise at 880Hz Output Rate 200nVRMS Noise at 6.9Hz Output Rate with Simultaneous 50/60Hz Rejection 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, Each Conversion is Accurate Even After an Input Step Internal Oscillator—No External Components Pin Compatible with the LTC2410 24-Bit ADC in Narrow 16-Lead SSOP 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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