WM8945
Production Data
The AUXADC has 3 available input sources, which are SPKVDD, AUX1 and AUX2. Each of these
inputs is enabled by setting the respective bit in the AuxADC Source Register (R62). The WM8945
provides options to select the scaling and voltage reference for these inputs; these are described in
Table 57.
Note that the AUX1 and AUX2 pins should not be used as AUXADC inputs if they are used as audio
inputs. (See “Input Signal Path”.)
For each AUXADC measurement event (in Manual or Automatic modes), the WM8945 selects the
next enabled input source. Any number of inputs may be selected simultaneously; the AUXADC will
measure each on in turn. Note that only a single AUXADC measurement is made on any Manual or
Automatic trigger.
The control fields associated with initiating AUXADC measurements are defined in Table 56.
REGISTER
ADDRESS
BIT
LABEL
DEFAULT
DESCRIPTION
AUXADC Enable
R61 (3Dh)
AUX_ENA
15
0
AuxADC
Control
0 = Disabled
1 = Enabled
AUX_CVT_ENA
AUXADC Conversion Enable
0 = Disabled
14
0
1 = Enabled
In automatic mode, conversions are
enabled by setting this bit.
In manual mode (AUX_RATE = 0),
setting this bit will initiate a
conversion; the bit is reset
automatically.
AUX_RATE [4:0]
AUX_BATT_SEL
AUXADC Conversion Rate
0_0000 = Manual conversion
0_0001 = 16Hz
4:0
0_0000
0_0010 = 32Hz
…(16Hz steps)
1_1111 = 496Hz
R62 (3Eh)
AUXADC Battery (SPKVDD) input
select
8
0
AuxADC
Source
0 = Disable Battery (SPKVDD)
measurement
1 = Enable Battery (SPKVDD)
measurement
AUX_AUX2_SE
L
AUXADC AUX2 input select
0 = Disable AUX2 measurement
1 = Enable AUX2 measurement
AUXADC AUX1 input select
0 = Disable AUX1 measurement
1 = Enable AUX1 measurement
1
0
0
0
AUX_AUX1_SE
L
Table 56 AUXADC Control
AUXADC INPUT CONFIGURATION
For inputs AUX1 and AUX2, the AUXADC uses either LDOVDD/2 or the 1.5V (nominal) bandgap as a
reference. This is selected independently for each AUX input, as described in Table 57. Selecting the
bandgap as a reference provides additional immunity to any noise on the supply rails.
The internal bandgap reference is nominally 1.5V. Note that this value is not trimmed and may vary
significantly (+/-10%) between different devices. When using this reference, the internal bandgap
reference must be enabled by setting the BG_ENA register, as described in Table 57.
PD, May 2011, Rev 4.1
84
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WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
