PCM1608YSLASH2K datasheet(25/29 Pages) TI

25 / 29 page

PCM1608

SBAS164A

POWER SUPPLIES AND GROUNDING

The PCM1608 requires a +5V analog supply and a +3.3V

digital supply. The +5V supply is used to power the DAC

analog and output filter circuitry, while the +3.3V supply is

used to power the digital filter and serial interface circuitry.

For best performance, the +3.3V supply should be derived

from the +5V supply using a linear regulator (see Figure 13).

Two capacitors are required for supply bypassing (see Fig-

ure 12). These capacitors should be located as close as

possible to the PCM1608 package. The 10

µF capacitors

should be tantalum or aluminum electrolytic, while the

0.1

µF capacitors are ceramic (X7R type is recommended

for surface-mount applications).

DAC OUTPUT FILTER CIRCUITS

Delta-sigma DACs utilize noise-shaping techniques to im-

prove in-band Signal-to-Noise Ratio (SNR) performance at

the expense of generating increased out-of-band noise above

the Nyquist Frequency, or fS/2. The out-of-band noise must

be low-pass filtered in order to provide the optimal converter

performance. This is accomplished by a combination of on-

chip and external low-pass filtering.

Figures 14 and 15 show the recommended external low-pass

active filter circuits for dual- and single-supply applications.

These circuits are second-order Butterworth filters using the

Multiple FeedBack (MFB) circuit arrangement, which re-

duces sensitivity to passive component variations over fre-

quency and temperature. For more information regarding

MFB active filter design, please refer to the Texas Instru-

ments Applications Bulletin AB-034, available from our

web site (www.ti.com), or your local Texas Instruments

sales office.

Since the overall system performance is defined by the quality

of the DACs and their associated analog output circuitry,

high-quality audio op amps are recommended for the active

filters. The OPA2134 and OPA2353 dual op amps from

Texas Instruments are shown in Figures 14 and 15, and are

recommended for use with the PCM1608.

FIGURE 14. Dual Supply Filter Circuit.

FIGURE 15. Single-Supply Filter Circuit.

OUT

OPA2134

V ≈ –

OUT

To Additional

Low-Pass Filter

Circuits

OPA2134

OPA337

µF

COM

PCM1608

V ≈ –

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