TDA7572 datasheet(44/64 Pages) STMICROELECTRONICS

44 / 64 page

DAC

TDA7572

44/64

DAC

A one channel DAC is provided. A balance between die area and functionality has been

made - the interpolator function required for full bandwidth operation has been off-loaded to

an external DSP. This allows Bass-only operation of the DAC without any processing

assistance, while full bandwidth audio requires external interpolation assistance.

The DAC has a differential output:

●

positive output DAC1(32)

●

negative output DAC2(31)

On these pins are present a four level squared wave, composed by the differences of two

PWM wave have one an amplitude 16 times lower than the other. The output voltage on

DAC1 and DAC2 is compatible to the digital supply VDIG.

Figure 7.

DAC circuit diagram

where is filtered by means of capacitors and put in the AOUT Differential to single-ended

input, as reported in the picture above. The maximum signal present output of converter is

1.4 Vrms. The setting to use for the Diff-to-SE converter is Gain= -3dB

(INLEVEL1=0,INLEVEL0=0).

Communication is through a standard I2S port. I2C is available too.

Acting on the I2C Control registers it is possible turn-on the DAC (DACEnb) and choose the

configuration (Fratio(1:0)). With Fratio = "00"/"01" the configuration is for bass only. The

Input sample frequency is 48kHz (Fs). In case of Fratio = "10" the configuration is for full

band. The input sample rate for this case is 96kHz (Fs) and the first x2 interpolator has to be

implemented off-line in the DSP. A well checked structure to realize could be the following:

Coefficients: -11,11,-16,22,-30,40,-53,69,-91,122,-168,247,-426,1300,2047,1300,….

Oversampling

Increasing word rate from Fs to 2Fs.

Filter

Type

Remez filter, half band

Taps, bit

57, 12

Attenuation

50db attenuation out of 0.55Fs

Coefficients It is an Half-Band filter then we have only 15

coefficients (see following)

R=20k

SVR/DGND

RF=4.7k

AC00019

R=2.5k

INP

INM

DAC2

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