REV. A

AD1853

–10–

Control Register

The following table shows the functions of the control register. The control register is addressed by having a “01” in the bottom 2 bits

of the 16-bit SPI word. The top 14 bits are then used for the control register.

Bit 11

Bit 10

Bit 9:8

Bit 7

Bit 6

Bit 5:4

Bit 3:2

INT2

× Mode

INT4

× Mode

Number of

Soft Reset.

Soft Mute OR’d Serial Mode OR’d

De-Emphasis Filter

OR’d with Pin.

OR’d with Pin.

Bits in Right-

Default = 0

with Pin.

with Mode Pins.

Select.

Default = 0

Default = 0

Justified Serial

Default = 0

IDPMI:IDPM0

0:0 No Filter

Mode.

0:0 Right-Justified

0:1 44.1 kHz Filter

0:0 = 24

0:1 I

1:0 32 kHz Filter

0:1 = 20

1:0 Left-Justified

1:1 48 kHz Filter

1:0 = 16

1:1 DSP Mode

Default = 0.0

Default = 0:0

Default = 0:0

Mute

The AD1853 offers two methods of muting the analog output.

By asserting the MUTE (Pin 23) signal HI, both the left and

right channel are muted. As an alternative, the user can assert

the mute bit in the serial control register (Bit 6) HI. The AD1853

has been designed to minimize pops and clicks when muting

and unmuting the device by automatically “ramping” the gain

up or down. When the device is unmuted, the volume returns to

the value set in the volume register.

Analog Attenuation

The AD1853 also offers the choice of using IREF (Pin 10) to

attenuate by up to 50 dB in the analog domain. This feature can

be used as an analog volume control. It is also a convenient

place to add a compressor/limiter gain control signal.

Output Drive, Buffering and Loading

The AD1853 analog output stage is able to drive a 1 k

Ω (in

series with 2 nF) load. The analog outputs are usually ac

coupled with a 10

µF capacitor.

De-Emphasis

The AD1853 has a built-in de-emphasis filter that can be used

to decode CDs that have been encoded with the standard

“Redbook” 50

µs/15 µs emphasis response curve. Three curves

are available; one each for 32 kHz, 44.1 kHz and 48 kHz sam-

pling rates. The external “DEEMP” pin (Pin 9) turns on the

44.1 kHz de-emphasis filter. The other filters may be selected

by writing to control Bits 2 and 3 in the control register. If the

SPI port is used to control the de-emphasis filter, the external

DEEMP pin should be tied LO.

Control Signals

The IDPM0 and IDPM1 control inputs are normally con-

nected HI or LO to establish the operating state of the AD1853.

They can be changed dynamically (and asynchronously to

LRCLK and the master clock), but it is possible that a click

or pop sound may result during the transition from one serial

mode to another. If possible, the AD1853 should be placed in

mute before such a change is made.

Figures 9–14 show the calculated frequency response of the

digital interpolation filters. Figures 15–27 show the performance

of the AD1853 as measured by an Audio Precision System 2

Cascade. For the wideband plots, the noise floor shown in the

plots is higher than the actual noise floor of the AD1853. This is

caused by the higher noise floor of the “High Bandwidth” ADC

used in the Audio Precision measurement system. The two-tone

test shown in Figure 18 is per the SMPTE standard for measur-

ing Intermodulation Distortion.

FREQUENCY – kHz

0.001

0

210

12

14

16

20

0.0008

0.0006

0.0004

0.0002

0

–0.0002

–0.0004

–0.0006

–0.0008

–0.001

46

8

18

Figure 9. Passband Response 8

× Mode, 48 kHz Sample

Rate

FREQUENCY – kHz

0

–60

–100

–160

–20

–40

–80

–120

–140

0

150

200

50

100

250

300

350

Figure 10. Complete Response, 8

× Mode, 48 kHz

Sample Rate