PCM1741

12

SBAS175

REGISTER DEFINITIONS

B15

B14

B13

B12

B11

B10

B9

B8

B7

B6

B5

B4

B3

B2

B1

B0

Register 16

0

IDX6

IDX5

IDX4

IDX3

IDX2

IDX1

IDX0

AT17

AT16

AT15

AT14

AT13

AT12

AT11

AT10

Register 17

0

IDX6

IDX5

IDX4

IDX3

IDX2

IDX1

IDX0

AT27

AT26

AT25

AT24

AT23

AT22

AT21

AT20

ATx[7:0]

Digital Attenuation Level Setting

where x = 1 or 2, corresponding to the DAC output VOUTL (x = 1) and VOUTR (x = 2).

Default Value: 1111 1111B

Each DAC channel (VOUTL and VOUTR) includes a digital attenuator function. The attenuation level may be

set from 0dB to –63dB, in 0.5dB steps. Changes in attentuator levels are made by incrementing or

decrementing, by one step (0.5dB), for every 8/fS time interval until the programmed attenuator setting is

reached. Alternatively, the attenuator level may be set to infinite attenuation (or mute). The attenuation data

for each channel can be set individually.

The attenuation level may be set using the formula below.

Attenuation Level (dB) = 0.5 (ATx[7:0]DEC – 255)

where: ATx[7:0]DEC = 0 through 255

for: ATx[7:0]DEC = 0 through 128, the attenuator is set to infinite attenuation.

The following table shows attenuator levels for various settings.

ATx[7:0]

Decimal Value

Attenuator Level Setting

1111 1111B

255

0dB, No Attenuation (default)

1111 1110B

254

–0.5dB

1111 1101B

253

–1.0dB

1000 0011B

131

–62.0dB

1000 0010B

130

–62.5dB

1000 0001B

129

–63.0dB

1000 0000B

128

Mute

••

•

••

•

••

•

0000 0000B

0

Mute

B15

B14

B13

B12

B11

B10

B9

B8

B7

B6

B5

B4

B3

B2

B1

B0

Register 18

0

IDX6

IDX5

IDX4

IDX3

IDX2

IDX1

IDX0

RSV

OVER

RSV

RSV

RSV

RSV

MUT2

MUT1

MUTx

Soft Mute Control

Where x = 1 or 2, corresponding to the DAC output VOUTL (x = 1) and VOUTR (x = 2).

Default Value: 0

MUTx = 0

Mute Disabled (default)

MUTx = 1

Mute Enabled

The mute bits, MUT1 and MUT2, are used to enable or disable the Soft Mute function for the corresponding

DAC outputs, VOUTL and VOUTR. The Soft Mute function is incorporated into the digital attenuators. When

Mute is disabled (MUTx = 0), the attenuator and DAC operate normally. When Mute is enabled by setting

MUTx = 1, the digital attenuator for the corresponding output will be decreased from the current setting to

the infinite attenuation setting, one attenuator step (0.5dB) at a time. This provides a “pop”-free muting of the

DAC output. By setting MUTx = 0, the attenuator will be increased one step at a time to a previously

programmed attenuation level.

OVER

Oversampling Rate Control

Default Value: 0

OVER = 0

64x Oversampling (default)

OVER = 1

128x Oversampling

The OVER bit is used to control the oversampling rate of the delta-sigma DACs.