JAJSDU5A August 2017 – February 2020 ADS114S06B , ADS114S08B
PRODUCTION DATA.
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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. Table 10 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.