SBAS815A February 2017 – June 2017 ADS114S06 , ADS114S08
PRODUCTION DATA.
Refer to the PDF data sheet for device specific package drawings
The offset calibration word is 16 bits, consisting of two 8-bit registers, as shown in the two registers starting with offset calibration register 1. The offset value is twos complement format with a maximum positive value equal to 7FFFh, and a maximum negative value equal to 8000h. This value is subtracted from each output reading as an offset correction. A register value equal to 0000h has no offset correction. If global chop mode is enabled, the offset calibration register is disabled. Table 21 shows example settings of the offset register.
OFC REGISTER VALUE | OFFSET CALIBRATED OUTPUT CODE(1) |
---|---|
0001h | FFFFh |
0000h | 0000h |
FFFFh | 0001h |
The user can select how many samples (1, 4, 8, or 16) to average for self or system offset calibration using the CAL_SAMP[1:0] bits in the system control register (09h). Fewer readings shorten the calibration time but also provide less accuracy. Averaging more readings takes longer but yields a more accurate calibration result by reducing the noise level.
Two commands can be used to perform offset calibration. SFOCAL is a self offset calibration that internally sets the input to mid-scale using the SYS_MON[2:0] = 001 setting and takes a measurement of the offset. SYOCAL is a system offset calibration where the user must input a null voltage to calibrate the system offset. After either command is issued, the OFC register is updated.
After an offset calibration is performed, the device starts a new conversion and DRDY falls to indicate a new conversion has completed.