WM9713 datasheet(73/111 Pages) WOLFSON

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Preliminary Technical Data

WM9713L

PTD, March 2004, Rev 2.2

ADDITIONAL FEATURES

AUXILIARY ADC INPUTS

The ADC used for touchpanel digitisation can also be used for the sole purpose of auxiliary

measurements, provided that it is enabled (register 78h, PRP = 11). The WM9713L has three pins

that can be used as auxiliary ADC inputs:

•

MIC2A / COMP1 / AUX1 (pin 29)

•

MIC2B / COMP2 / AUX2 (pin 30)

•

WIPER / AUX4 (pin 12)

Additionally, the speaker supply (SPKVDD) can be used as an auxillary ADC input through an on-

chip potential divider giving an input to the auxillary ADC of SPKVDD/3. This input is referred to as

the AUX3 input (see Figure 16).

Note that pin 12 connects to the wiper of a 5-wire touchpanel wiper function. Auxiliary measurements

taken on pin 12 are only meaningful when it is not connected to a touchpanel (i.e. a 4-wire

touchpanel, or no touchpanel at all, is used). Pins 29 and 30 are also used as comparator inputs (see

Battery Alarm and Battery Measurement), but auxiliary measurements can still be taken on these

pins at any time. The ADCSEL control bits select between different ADC inputs, as shown in Table

56.

The ADCSEL control bits determine which type of measurement is performed (see below). When

performing auxiliary conversions the co-ordinate mode bit, COO, should be off (0).

If CTC=0 then only one of the ADCSEL[7:1] bits should be set. If operating in continuous mode

(CTC=1), then more than one ADCSEL[7:1] bit may be set, and conversions will be performed

cyclically in the following order => “AUX1,AUX2,AUX3,AUX4…” – dependent on which bits are set.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

ADCSEL_AUX4

Enable AUX4 measurement (pin12)

ADCSEL_AUX3

Enable AUX3 measurement (SPKVDD)

ADCSEL_AUX2

Enable AUX2 measurement (pin30)

ADCSEL_AUX1

Enable AUX1 measurement (pin29)

74h

COO

Enable co-ordinate mode – for touchpanel

conversions only (see “Controlling the

Touchpanel Interface”)

Table 56 Auxiliary ADC Measurements

Auxiliary ADC measurements are initiated in the same way as touchpanel measurements, and the

data is returned in the same manner. Please refer to the “Controlling the Touchpanel Interface”

section.

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