WM8352
Production Data
19.5 CALIBRATION
The on-chip reference VREF provides a highly accurate reference voltage to the AUXADC. For best
measurement accuracy, the WM8352 provides a way to determine the voltage offset of the
AUXADC’s VREF buffer and the gain error introduced by scaling the AUXADC input. Measured data
can then be adjusted accordingly, eliminating these errors.
To determine the buffer’s offset, the AUXADC AUX3 input is disconnected from the AUX3 pin and
connected to the unbuffered VREF voltage. Note that input scaling must be used, (i.e.
AUXADC_SCALE3 = 10 or 11), in order to ensure that the AUXADC input is within the measurable
range. Measuring this voltage using the buffered VREF as the reference (AUXADC_REF3 = 1)
makes it possible to calculate the combined error.
ADDRESS
R145 (91h)
Digitizer Control
(2)
BIT
LABEL
DEFAULT
DESCRIPTION
2
AUXADC_CAL
0
Configure AUX3 input to be the
VREF supply for AUXADC
calibration.
0 = AUX3 input connected to
AUX3 pin
1 = AUX3 input connected to
unbuffered VREF
Table 118 AUXADC Calibration
PD, February 2011, Rev 4.4
176
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
