wm8941 Wolfson Microelectronics plc, wm8941 Datasheet - Page 49

• Manufacturer Part Number: wm8941
• Description: Mono Codec With Speaker Driver And Video Buffer
• Manufacturer: Wolfson Microelectronics plc

Production Data
w
OUTPUT SWITCH
Table 39 Disabled Outputs to VREF Resistance
Table 40 Unused Output Pin Tie-off Options
A dedicated buffer is available for tying off unused analogue I/O pins as shown in Figure 21. This
buffer can be enabled using the BUFIOEN register bit.
Table 40 summarises the tie-off options for the speaker and mono output pins.
When the device is configured with a 2-wire interface the CSB/GPIO pin can be used as a switch
control input to automatically disable the speaker outputs and enable the mono output. As an
example, when a line is plugged into a jack socket. In this mode, enabled by setting GPIOSEL=001,
pin CSB/GPIO switches between mono and speaker outputs (e.g. when pin 12 is connected to a
mechanical switch in the headphone socket to detect plug-in). The GPIOPOL bit reverses the polarity
of the CSB/GPIO input pin. In 3-wire control mode the GPIO pin can be use in the same way.
Note that the speaker outputs and the mono output must be enabled for this function to work (see
Table 41). The GPIO has an internal de-bounce circuit when in this mode in order to prevent the
output enables from toggling multiple times due to input glitches. This de-bounce circuit is clocked
from a slow clock with period 2
Figure 21 Unused Input/Output Pin Tie-off Buffers
R49
SPKN/PEN
MONOEN/
REGISTER
ADDRESS
0
0
1
0
BIT
VROI
X
0
1
VROI
LABEL
21
x MCLK, enabled using the SLOWCLKEN register bit.
Output enabled (DC level=AVDD/2)
OUTPUT CONFIGURATION
30kΩ tieoff to AVDD/2
1kΩ tieoff to AVDD/2
0
DEFAULT
VREF (AVDD/2) to analogue output
resistance
0: approx 1kΩ
1: approx 30 kΩ
DESCRIPTION
PD, Rev 4.0, August 2008
WM8941
49