WM8720

Production Data

w

PD Rev 4.0. February 2005

11

The MUTE pin behaves as a bi-directional function, that is, as an input to select mute or NOT-mute,

or as an output indication of automute operation. MUTE is active high; taking the pin high causes the

filters to soft mute, ramping down the audio signal over a few milliseconds. Taking MUTE low again

allows data into the filter.

The automute function detects a series of zero value audio samples of 1024 samples long being

applied to both left and right channels. After such an event, a latch is set whose output (automuted)

is wire OR’ed through a 10kohm resistor to the MUTE pin. Thus if the MUTE pin is not being driven,

the automute function will assert MUTE.

If MUTE is tied low, automute is overridden and will not mute. If MUTE is driven from a source

follower, or diode, then both mute and automute functions are available. If MUTE is not driven,

automute appears as a weak output (10k source impedance) so can be used to drive external

mute circuits.

The automute signal is AND’ed with IZD, this qualified mute signal then being OR’ed into the

SOFTMUTE control. Therefore, in software mode, automute operation may be controlled with IZD

control bit.

I

In hardware mode, pins 4 and 5 become input controls for selection of input data format type, and

input data word length, see Table 4. I

enough bit clocks are sent.

ML/I

MC/IWL – PIN 5

INPUT DATA MODE

0

0

16-bit normal

0

1

20-bit normal

1

0

24-bit normal

1

1

I

Table 4 Control of Input Data Format Type and Input Data Word Length

DM DE-EMPHASIS

In hardware mode, pin 6 becomes an input control for selection of de-emphasis filtering to be

applied. See Figure 8.

DM

0

De-emphasis off

DM

1

De-emphasis on

Table 5 De-emphasis Control

PWDN POWERDOWN CONTROL

In both hardware and software modes, this pin selects powerdown of the entire device when taken

high.

PWDN

0

Device powered up

PWDN

1

Device powered down

Table 6 Powerdown Control

SOFTWARE CONTROL INTERFACE

The WM8720 can be controlled using a 3-wire serial interface. MD/DM (pin 6) is used for the program

data, MC/IWL (pin 5) is used to clock in the program data and ML/I2S (pin 4) is use to latch in the

program data. The 3-wire interface protocol is shown in Figure 7.

ML/I2S

MC/IWL

MD/DM

D15

D6

D7

D8

D9

D10

D11

D12

D13

D14

D1

D2

D3

D4

D5

D0

Figure 7 3-Wire Serial Interface