DF1706ESLASH2K datasheet(13/16 Pages) TI

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DF1706

SBAS182

ATC

Attenuator Control.

This bit is used to determine whether the Left

and Right channel attenuators operate with inde-

pendent data, or use common data (the Left

channel data in bits AL[7:0] of register MODE0).

When ATC = 0, the Left and Right channel

attenuator data is independent.

When ATC = 1, the Left and Right channel

attenuators use common data.

SRO

Digital Filter Roll-Off Selection.

When SRO = 0, sharp roll-off is selected.

When SRO = 1, slow roll-off is selected.

CKO

CLKO Output Frequency Selection.

When CKO = 0, the CLKO frequency is the

same as the clock at the XTI input.

When CKO =1, the CLKO frequency is half of

the XTI input clock frequency.

SF[1:0]

Sampling Frequency Selection for the De-Em-

phasis Function.

SF1 SF0

Description

44.1 kHz

Reserved

48 kHz

32 kHz

APPLICATIONS INFORMATION

PCB LAYOUT GUIDELINES

In order to obtain the specified performance from the DF1706

and its associated D/A converters, proper printed circuit

board layout is essential. Figure 11 shows two approaches

for obtaining the best audio performance.

Figure 11(a) shows a standard, mixed signal layout scheme.

The board is divided into digital and analog sections, each

with its own ground. The ground areas should be put on a

split-plane, separate from the routing and power layers. The

DF1706 and all digital circuitry should be placed over the

digital section, while the audio D/A converter(s) and analog

circuitry should be located over the analog section of the

board. A common connection between the digital and analog

grounds is required and is done at a single point as shown.

For Figure 11(a), digital signals should be routed from the

DF1706 to the audio D/A converter(s) using short, direct

connections

to reduce the amount of radiated high-fre-

quency energy. If necessary, series resistors may be placed

in the clock and data signal paths to reduce or eliminate any

overshoot or undershoot present on these signals. A value of

Ω to 100Ω is recommended as a starting point, but the

designer should experiment with the resistor values in order

to obtain the best results.

Figure 11(b) shows an improved method for high-perfor-

mance, mixed signal board layout. This method adds digital

isolation between the DF1706 and the audio D/A converter(s),

and provides complete isolation between the digital and

analog sections of the board. The ISO150 dual digital

coupler provides excellent isolation, and operates at speeds

up to 80Mbps.

POWER SUPPLIES AND BYPASSING

The DF1706 requires a single +5V power supply for opera-

tion. The power supply should be bypassed by a 10

µF and

0.1

µF parallel capacitor combination. The capacitors should

be placed as close as possible to VDD (pin 22). Aluminum

electrolytics or tantalum capacitors can be used for the 10

µF

value, while ceramics may be used for the 0.1

µF value.

BASIC CIRCUIT CONNECTIONS

See Figures 12 and 13 for basic circuit connections of the

DF1706. Figure 12 shows connections for Hardware mode

controls, while Figure 13 shows connections for Software

mode controls. Notice the placement of C1 and C2 in both

figures, as they are physically close to the DF1706.

TYPICAL APPLICATIONS

The DF1706 will typically be used in high performance

audio equipment, in conjunction with high performance

audio D/A converters. Figure 14 shows a typical application

circuit example, employing the DF1706, a digital audio

receiver, and two PCM1704 24-bit, 192kHz audio D/A

converter(s).

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