ADS1246IPWR

The ADS1246IPWR is a highly integrated precision 24-bit delta-sigma analog-to-digital converter from Texas Instruments, optimized for precision sensor measurement applications. As a member of the ADS124x family (which also includes the 4-channel ADS1247 and 8-channel ADS1248), the single-channel ADS1246 provides the same high performance core in a smaller, more cost-effective package for applications requiring only one measurement channel. At the heart of the device is a third-order delta-sigma modulator followed by a programmable digital filter that provides single-cycle settling, meaning full accuracy is achieved on the very first conversion after a channel change or start command – this is particularly valuable in multiplexed systems. The onboard low-noise programmable gain amplifier offers eight gain settings from 1 to 128, allowing the device to handle signals ranging from full-scale volts down to microvolt-level sensor outputs. At the highest gain setting, the input-referred noise is only 48 nVrms, enabling precise measurement of very small signals such as those from thermocouples and strain gauges. The digital filter provides simultaneous rejection of both 50Hz and 60Hz line frequencies at 20 SPS data rate, with rejection exceeding 90 dB. The ADS1246 includes many integrated features that simplify sensor interface design: internal 2.048V reference with only 10 ppm/C maximum drift, internal oscillator eliminating the need for an external crystal, sensor burn-out detection current sources for detecting open or shorted sensor connections, and an internal temperature sensor for cold-junction compensation in thermocouple applications. Self and system calibration capabilities allow offset and gain errors to be corrected in the field. The device operates from a 2.7V to 5.25V analog supply and 2.7V to 5.25V digital supply, with total power dissipation of only 2.3 mW at 5V and 20 SPS. A power-down mode reduces current to 0.3 microamps for battery-powered applications. The ADS1246IPWR is packaged in a 16-lead TSSOP with tape and reel packaging (PWR suffix).

The ADS1246 is a delta-sigma ADC that uses oversampling and noise shaping to achieve high 24-bit resolution. The analog input signal is first passed through the programmable gain amplifier (PGA), which amplifies the signal to optimize use of the ADC full-scale range. The PGA gain is selected through register settings from 1 to 128. The amplified signal is then fed to a third-order delta-sigma modulator, which samples the input at a very high rate (much higher than the output data rate) and produces a 1-bit output stream. The modulator shapes the quantization noise so that most of it falls at frequencies above the signal band, where it can be easily removed. Following the modulator is a digital decimation filter that converts the high-rate 1-bit stream into lower-rate multi-bit samples at the programmed data rate. This digital filter also provides the antialiasing function, greatly reducing the need for analog input filtering. The filter can be programmed for data rates from 5 SPS to 2000 SPS, with a trade-off between noise resolution and speed: lower data rates provide more filtering and therefore better noise performance, while higher rates allow faster measurements. At data rates of 20 SPS and below, the filter is specifically designed to reject both 50Hz and 60Hz line frequencies simultaneously, which is very useful for industrial sensor applications where power line interference is a common concern. A key feature is single-cycle settling: the digital filter achieves full accuracy on the first output sample after a change in input or gain, meaning that even when rapidly switching between measurement configurations, there is no need to discard multiple settling samples. The internal reference voltage of 2.048V is generated by a low-drift bandgap circuit, and the internal oscillator runs at approximately 4.096 MHz, providing all the necessary clock signals for the modulator and digital filter. Communication with the device is through an SPI-compatible serial interface, and the DRDY (data ready) output pin indicates when conversion data is available to read.

• Precision temperature measurement with RTDs, thermocouples, and thermistors
• Weigh scales and load cell signal conditioning
• Pressure transmitters and industrial pressure measurement
• Strain gauge measurement and force sensors
• Flow meters and industrial process control
• Data acquisition systems and data loggers
• Portable precision instrumentation
• Factory automation and PLC analog input modules
• Medical diagnostic and measurement equipment
• Calibration standards and reference measurement systems