WM8945ECSSLASHR datasheet(85/169 Pages) WOLFSON

85 / 169 page

Production Data

WM8945

PD, May 2011, Rev 4.1

For SPKVDD measurement, the SPKVDD voltage is connected to a potential divider in order to

reduce it to a suitable level. Two different scaling factors are available, controlled by the

AUX_BATT_SCALE register bit. The scaling factor should be selected such that the scaled output is

less than the maximum measurable level (LDOVDD).

For optimum measurement of the SPKVDD voltage, the SPKVDD potential divider can be connected

to the AUX1 pin, allowing an external capacitor to be used to filter noise from the SPKVDD supply.

This is enabled by setting the AUX_AUX1_FILTB register bit. This option can only be used when

AUX1 is not also used as an input to the AUXADC.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R54 (36h)

Bandgap

BG_ENA

Bandgap Reference Control

0 = Disabled

1 = Enabled

R63 (3Fh)

AuxADC

Config

AUX_AUX1_

FILTB

AUXADC Battery (SPKVDD)

measurement filter control

0 = Disabled

1 = Enabled

When AUX_AUX1_FILTB is set, the

Battery (SPKVDD) measurement

point is connected to the AUX1 pin,

allowing an external capacitor to be

used to filter noise.

AUX_BATT_

SCALE

AUXADC Battery (SPKVDD)

measurement divider control

0 = 0.45 x SPKVDD

(Note that 0.45 x 3.3V = 1.485V)

1 = 0.41 x SPKVDD

(Note that 0.41 x 3.6V = 1.476V)

AUX_AUX2_

REF

AUXADC AUX2 reference select

0 = LDOVDD/2

1 = 1.5V (nominal) Bandgap

AUX_AUX1_

REF

AUXADC AUX1 reference select

0 = LDOVDD/2

1 = 1.5V (nominal) Bandgap

Table 57 AUXADC Input Configuration

AUXADC READBACK

Measured data from the AUXADC is read via the AuxADC Data Register (R60), which contains two

fields. The AUXADC Data Source is indicated in the AUX_DATA_SRC field; the associated

measurement data is contained in the AUX_DATA field.

Reading from the AuxADC Data Register returns a 12-bit code which represents the most recent

AUXADC measurement on the associated channel. It should be noted that every time an AUXADC

measurement is written to the AuxADC Data Register, the previous data is overwritten – the host

processor should ensure that data is read from this register before it is overwritten.

The 12-bit AUX_DATA field can be equated to the actual voltage by scaling according to the

applicable reference source. The full-scale value of AUX_DATA corresponds to the LDOVDD voltage

level.

The AUXADC interrupts can be used to indicate when new data is available – see “Interrupts”. A

GPIO pin configured as “AUX_DONE” can also be used to indicate when new data is available – see

“General Purpose Input / Output”.

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