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24-bit converter misses hum, not codes
Joshua Israelsohn -- EDN, 12/7/2000
Linear Technology's LTC2413 Dconverter for process-measurement and -control applications rejects 49- to 61-Hz normal-mode signals by 87 dB minimum and common-mode signals by 140 dB. Additionally, because the digital filter carries no data forward to successive conversions, you can multiplex the inputs at a 7-conversion/sec rate. The 2413 offers 24-bit resolution with no missing codes, 14-ppm integral nonlinearity, and 2.5-µV offset error, all worst case over temperature. Typical offset drift is 10 nV/°C or 2 LSB over temperature, assuming a ±2.5V input range, less than the typical rms output noise of 800 nV or about 3 LSB under the same conditions.
The front end features differential signal and reference inputs for simple connection to a variety of bridge and single-ended sensors. An on-chip conversion oscillator requires no external components. Conversion data is available through a three-wire SPI interface at the end of each conversion cycle without need for multicycle settling times for the digital filter. The converter enters a low-power sleep mode after it completes a conversion and stores the result in a register that immediately clocks out data on demand. Available in a 16-pin SSOP, the $8.30 (1000) converter draws a maximum of 300 µA during conversions and 30 µA during the sleep mode.
