WM8945ECSSLASHR datasheet(84/169 Pages) WOLFSON

84 / 169 page

WM8945

Production Data

PD, May 2011, Rev 4.1

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.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R61 (3Dh)

AuxADC

Control

AUX_ENA

AUXADC Enable

0 = Disabled

1 = Enabled

AUX_CVT_ENA

AUXADC Conversion Enable

0 = Disabled

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.

4:0

AUX_RATE [4:0]

0_0000

AUXADC Conversion Rate

0_0000 = Manual conversion

0_0001 = 16Hz

0_0010 = 32Hz

…(16Hz steps)

1_1111 = 496Hz

R62 (3Eh)

AuxADC

Source

AUX_BATT_SEL

AUXADC Battery (SPKVDD) input

select

0 = Disable Battery (SPKVDD)

measurement

1 = Enable Battery (SPKVDD)

measurement

AUX_AUX2_SE

AUXADC AUX2 input select

0 = Disable AUX2 measurement

1 = Enable AUX2 measurement

AUX_AUX1_SE

AUXADC AUX1 input select

0 = Disable AUX1 measurement

1 = Enable AUX1 measurement

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.

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