24-Bit High Speed Differential ∆∑ ADC with Selectable Speed/Resolution

The LTC2440 is a high speed 24-bit No Latency ∆∑™ 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.

Applications

* High Speed Multiplexing

* Weight Scales

* Auto Ranging 6-Digit DVMs

* Direct Temperature Measurement

* High Speed Data Acquisition

* 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