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APPLICATION INFORMATION

Connection Diagram

1

2

3

4

5

6

7

8

BCK

DATA

LRCK

DGND

V

DD

V

CC

V

OUTL

V

OUTR

16

15

14

13

12

11

10

9

SCK

ML

MC

MD

ZEROL/NA

ZEROR/ZEROA

V

COM

AGND

Post LPF

+3.3V

Regulator

Mode

Control

Zero Mute

Control

System Clock

PCM

Audio Data

Input

+5V V

CC

L−Chan OUT

10 F

10

µF

+

+

10

µF

Post LPF

R−Chan OUT

µ

Power Supplies and Grounding

DAC Output Filter Circuits

PCM1742

SBAS176A – DECEMBER 2000 – REVISED APRIL 2005

A basic connection diagram is shown in Figure 28, with the necessary power-supply bypassing and decoupling

components. Texas Instruments recommends using the component values shown in Figure 28 for all designs.

Figure 28. Basic Connection Diagram

The use of series resistors (22

Ω to 100 Ω) is recommended for the SCK, LRCK, BCK, and DATA inputs. The

series resistor combines with stray PCB and device input capacitance to form a low-pass filter that reduces

high-frequency noise emissions and helps to dampen glitches and ringing present on clock and data lines.

The PCM1742 requires a 5-V analog supply (VCC) and a 3.3-V digital supply (VDD). The 5-V supply is used to

power the DAC analog and output-filter circuitry, while the 3.3-V supply is used to power the digital filter and

serial interface circuitry. For best performance, the 3.3-V supply should be derived from the 5-V supply using a

linear regulator, as shown in Figure 28. The REG1117-3.3 from Texas Instruments is an ideal choice for this

application.

Proper power-supply bypassing is shown in Figure 28. The 10-

µF capacitors should be tantalum or aluminum

electrolytic.

Delta-sigma DACs use noise-shaping techniques to improve 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.

Figure 27(a) and Figure 29 show the recommended external low-pass active filter circuits for single- and

dual-supply applications. These circuits are second-order Butterworth filters using a multiple feedback (MFB)

circuit arrangement that reduces sensitivity to passive component variations over frequency and temperature. For

more information regarding MFB active filter design, see FilterPro™ MFB and Sallen-Key Low-Pass Filter Design

Program (SBFA001), available from the TI Web site at http://www.ti.com.

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