JAJSHV4C January 2014 – August 2019 ADS1283
PRODUCTION DATA.
The ADC modulator can produce low-level idle tones that appear in the spectrum when there is no signal input or when low-level signal inputs are present to the ADC. The ADC provides an optional dc offset voltage designed to shift the idle tones to the stop band of digital filter response, where the idle tones are reduced. The internal offset is applied to the modulator input; therefore, the offset voltage amplitude is independent of PGA gain. For all ADS1283 versions, the offset option is 100 mV. For the ADS1283B, a second offset option is 75 mV. The 75-mV offset optimally reduces idle tones under various gain, data rate, and chop mode settings.
The offset is enabled by the OFFSET1 and OFFSET0 bits (default is off). The offset voltage reduces the available input range 4% (3% for the 75 mV value) before the onset of clipped codes. The offset voltage can be calibrated by using the offset calibration register (OFC[2:0]). Use the offset calibration register to compensate the offset voltage, thereby restoring the full input voltage range. See Offset and Full-Scale Calibration Registers and Calibration Commands (OFSCAL and GANCAL) sections for more details.