WM9713 Datasheet, PDF (73/111 Pages) Wolfson Microelectronics plc – AC 97 AUDIO + TOUCHPANEL CODEC

Preliminary Technical Data
WM9713L
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.
BIT
LABEL
DEFAULT
DESCRIPTION
REGISTER
ADDRESS
74h
7
ADCSEL_AUX4
0
Enable AUX4 measurement (pin12)
6
ADCSEL_AUX3
0
Enable AUX3 measurement (SPKVDD)
5
ADCSEL_AUX2
0
Enable AUX2 measurement (pin30)
4
ADCSEL_AUX1
0
Enable AUX1 measurement (pin29)
0
COO
0
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.
1
PTD, March 2004, Rev 2.2
73