Features

• Up to 3.5kHz Output Rate
• Selectable Speed/Resolution
• 2µV_RMS Noise at 880Hz Output Rate
• 200nV_RMS 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 < V_CC < 5.5V, –40°C to 85°C)
• Differential Input and Differential Reference with GND to V_CC 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

Description

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/ 200nV_RMS to 3.5kHz/25µV_RMS) are programmed through a simple serial interface. Alternatively, by tying a single pin HIGH or LOW, a fast (880Hz/2µV_RMS) or ultralow noise (6.9Hz, 200nV_RMS, 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.