24-Bit High Speed 4-Channel ΔΣ ADC with Integrated Amplifier

The LTC2442 is an ultra high precision, variable speed, 24-bit ΔΣ™ ADC with integrated amplifier. The amplifier can be configured as a buffer for easy input drive of high impedance sensors. 1 part-per-million (ppm) linearity is achievable when the amplifier is configured in unity gain. External resistors can be used to set a gain for increased resolution of low level input signals. The positive and negative amplifier supply pins may be tied directly to VCC (4.5V to 5.5V) and GND or biased above VCC and below GND for rail-to-rail input signals.

The proprietary ΔΣ architecture ensures stable DC accuracy through continuous transparent calibration. Ten speed/resolution combinations from 6.9Hz/220nVRMS to 3.5kHz/25µVRMS can be selected with no latency or shift in DC accuracy. Additionally, a 2X speed mode can be selected enabling output rates up to 7kHz (8kHz with an external oscillator) with one cycle latency.

Any combination of single-ended (up to 4 inputs) or differential (up to 2 inputs) can be selected with a common mode input range from ground to VCC. While operating in the 1X speed mode the first conversion following a new speed/resolution or channel selection is valid.

Applications

* Auto Ranging 6-Digit DVMs

* High Speed Multiplexing

* Weight Scales

* Direct Temperature Measurement

* High Speed Data Acquisition

* 1ppm Linearity with No Missing Codes

* Integrated Amplifier for Direct Sensor Digitization

* 2 Differential or 4 Single-Ended Input Channels

* Up to 8kHz Output Rate (External fO)

* Up to 4kHz Multiplexing Rate (External fO)

* Selectable Speed/Resolution

* 2.1µVRMS Noise at 1.76kHz Output Rate

* 220nVRMS Noise at 13.8Hz Output Rate with Simultaneous 50Hz/60Hz Rejection

* Guaranteed Modulator Stability and Lock-Up Immunity for any Input and Reference Conditions

* <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

* 36-Lead SSOP Package