Advanced Information

WM8759

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AI Rev 3.0 September 2004

13

HARDWARE CONTROL MODES

The WM8759 is hardware programmable providing the user with options to select input audio data

format, de-emphasis and mute.

ENABLE OPERATION

Pin 4 (ENABLE) controls the operation of the chip. If ENABLE is low the device is held in a low

power state. If this pin is held high the device is powered up.

To ensure correct operation it is essential that there is a low to high transition on the ENABLE pin

after digital supplies have come on. This can be achieved by providing the ENABLE signal from

an external controller chip or by means of a simple RC network on the ENABLE pin. See

“Recommended External Components” in the “Application Information” section at the end of this

datasheet.

Note that the ENABLE pin should not be used as a mute pin or to temporarily silence the DAC

(between tracks of a CD for example). The ENABLE pin is not intended to be used as a mute

control but to allow entry into low power mode. Disabling the device via the ENABLE pin has the

effect of powering down the voltage on the CAP pin. Repeated enabling/disabling of the device

can cause audible pops at the output.

HIGH PERFORMANCE MODE

On the rising edge of ENABLE, the DEEMPH pin is sampled. If it is low the device powers up

normally. If it is high the device goes into a high performance and high power consumption state.

Once ENABLE is high, DEEMPH controls the selection of the de-emphasis filter.

INPUT AUDIO FORMAT SELECTION

FORMAT (pin 13) controls the data input format.

FORMAT

INPUT DATA MODE

0

16 bit right justified

1

16–24 bit I

Table 2 Input Audio Format Selection

Notes:

1.

In 16-24 bit I

high for a minimum of data width BCKINs and low for a minimum of data width BCKINs,

unless Note 2. For data widths greater than 24 bits, the LSB’s will be truncated and the

most significant 24 bits will be used by the internal processing.

2.

If exactly 16 BCKIN cycles occur in both the low and high period of LRCIN the WM8759 will

assume the data is 16-bit and accept the data accordingly.

INPUT DSP FORMAT SELECTION

FORMAT

50% LRCIN DUTY CYCLE

LRCIN of 4 BCKIN or Less Duration

0

16 bit

(MSB-first, right justified)

DSP format – ‘late’ mode

1

I

(Philips serial data protocol)

DSP format – ‘early’ mode

Table 3 DSP Interface Formats

DE-EMPHASIS CONTROL

DEEMPH (pin 12) is an input control for selection of de-emphasis filtering to be applied.

DEEMPH

DE-EMPHASIS

0

Off

1

On

Table 4 De-emphasis Control