Transducer interface arrangement including a sigma-delta modulator with offset correction and with gain setting

摘要

A transducer interface arrangement including sensor means (SM) for measuring a parameter such as temperature, pressure, ..., an Analog-to-Digital Converter (ADCb) including a Sigma-Delta Modulator (SDMb), and a selectable resistor string (SRSa). The data input of the Sigma-Delta Modulator is connected to the series combination of a first switched-capacitor module (SC1, SC1b), a first differential amplifier (A1), a second switched-capacitor module (SC2) and a second differential amplifier (A2), followed by a comparator (CP). The modulator further comprises a third (SC3) and a fourth (SC4) switched-capacitor module to which a reference voltage is applied and which are respectively connected to the input of the first and the second amplifier. To reduce the chip area and power consumption while increasing the performance of the arrangement, an offset canceling pre-amplifier to the A/D converter is advantageously replaced by a fifth switched-capacitor module (SC5), to which an offset voltage is applied. The offset voltage is provided, together with the reference voltage, by the selectable resistor string (SRSa). In addition to the improved offset correction, the present transducer interface arrangement is also provided with simple gain setting means. To this end, gain setting modules consisting of one or more switchable capacitive branches coupled in parallel with existing capacitors in the first switched-capacitor module (SC1b). The more branches which are added, the higher the gain.