AS3510_04 datasheet(6/20 Pages) AMSCO

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Product Brief AS3510

Rev. 1v2, June 2004

CONFIDENTIAL

Page 5 of 19

Functional Description

Audio DAC

Block Description

This block is the complete audio DAC delivering 93dB

dynamic range. It is comprised of a multibit sigma-delta

modulator with dither option and a switched-capacitor

analog filter. This architecture provides a high insensitivity

to clock jitter. A digital interpolation filter increases the

sample rate by a factor of 8 using 3 linear phase, half-band

filters cascaded, followed by a first order SINC interpolator

with a factor of 8. This filter eliminates the images of

baseband audio remaining only the image at 64* the input

sample rate. Optionally, a dither signal can be added that

may reduce eventual noise tones at the output. However,

the use of a multibit delta-sigma modulator already

provides extremely low noise tone energy.

Signal Description

Setting DACPD to ´1´ forces the analog section to power-

down. For Normal-Operation the I2S signals have to be

applied as shown below:

MCLK

LRCK

SCLK

SDATA(16)

SDATA(18)

64 MCLK cycles

Left Channel

64 MCLK cycles

Right Channel

Figure 2

I2S Waveforms

The LRCK defines if the transferred data is for the left or

right channel (L=left).

With the rising edge of the serial clock SCLK, the

inputdata gets strobed.

The data word at SDATA is max. 18 bit with MSB first and

2nd complement coded. All I2S signals change state with

falling edge of SCLK.

code

hex value

Max. positive code

1FFFF (hex)

00001 (hex)

00000 (hex)

-1

3FFFF (hex)

Max. negative code:

20000 (hex)

Table 4

I2S Code Values

If the dataword length is less than 18 bit, zeros have to be

added to avoid any offset value.

The frequency of master clock MCLK has to be 128 times

the input sample rate (F(LRCK)*128) with low jitter. The

rising edge of MCLK should be separated by >10ns from

LRCK edges.

There are 2 pins needed for the generation and decoupling

of reference-voltages for the DAC. AGND is AVDD/2 and

VREF is equal to AVDD. Both pins have high output

resistance which provides a suitable lowpass filter for

these reference voltages with external capacitors of 10uF

in parallel with 100nF.

The supply lines are separate for digital DVSS / DVDD and

analog AVSS / AVDD to minimise coupling influences.

The analog output is differential stereo signal at nodes

OUTRN, OUTRP and OUTLN, OUTLP respectively.

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