1

2

3

4

13

14

SCLK(fCLK-CAL)

CS

Sample

N

0

0

D11

D10

SDO

Data for Sample N

D1

D0

15

16

18

17

32

31

Sample

N+1

tCONV

tCAL

tACQ

tPH_CS

tSU_CSCK

tD_CKCS

ADS7044

SBAS682D – NOVEMBER 2014 – REVISED DECEMBER 2015

www.ti.com

8.4.1.2 Offset Calibration During Normal Operation

The offset can also be calibrated during normal device operation. Offset calibration can be done during normal

device operation if at least 32 SCLKs are provided in one serial transfer frame. During the first 14 SCLKs, the

device converts the sample acquired on the CS falling edge and provides data on the SDO output. The device

initiates the offset calibration on the 17th SCLK falling edge and calibration is completed on the 32nd SCLK

falling edge. The SDO output remains low after the 14th SCLK falling edge and SDO goes to 3-state after CS

goes high. If the device is provided with less than 32 SCLKs during a serial transfer frame, the OCR is not

updated. Table 3 provides the timing parameters for offset calibration during normal operation.

For subsequent samples, the device adjusts the conversion results with the value stored in OCR. The conversion

result adjusted with the value stored in the OCR is provided by the device on the SDO output. Figure 38 shows

the timing diagram for offset calibration during normal operation.

Table 3. Offset Calibration During Normal Operation

MIN

TYP

MAX

UNIT

fCLK-CAL

SCLK frequency for calibration for 2.25 V < AVDD < 3.6 V

16

MHz

fCLK-CAL

SCLK frequency for calibration for 1.65 V < AVDD < 2.25 V

12

MHz

tCAL

Calibration time during normal operation

16 tSCLK

ns

tACQ

Acquisition time

200

ns

tPH_CS

CS high time

tACQ

ns

Figure 38. Offset Calibration During Normal Operation Timing Diagram

22

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