WM8721

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WOLFSON MICROELECTRONICS LTD

PP Rev 1.3 November 2000

29

0

USB/

NORMAL

0

Mode Select

1 = USB mode (250/272fs)

0 = Normal mode (256/384fs)

1

BOSR

0

Base Over-Sampling Rate

USB Mode

0 = 250fs

1 = 272fs

Normal Mode

0 = 256fs

1 = 384fs

5:2

SR[3:0]

0000

DAC sample rate control;

See USB Mode and Normal Mode

Sample Rate sections for operation

0001000

Sampling

Control

6

CLKIDIV2

0

Core Clock divider select

1 = Core Clock is MCLK divide by 2

0 = Core Clock is MCLK

0001001

Active Control

0

ACTIVE

0

Activate Interface

1 = Active

0 = Inactive

0001111

Reset Register

8:0

RESET

not reset

Reset Register

Writing 00000000 to register resets

device

1110000

Test Failsafe

0

TESTFAIL

SAFE

0

Test Mode Failsafe Bit

1 = Test Mode Allowed

0 = Test Mode Locked Out

1110001

Analogue Test

Register 1

8:0

ATEST1[8:0]

0

Analogue Test Register 1

1110010

Analogue Test

Register 2

8:0

ATEST2[8:0]

0

Analogue Test Register 2

1110011

Digital Test

Register 1

8:0

DTEST1[8:0]

0

Digital Test Register 1

1110100

Digital Test

Register 2

8:0

DTEST2[8:0]

0

Digital Test Register 2

Table 19 Register Map Description

Note: All other bits not explicitly defined in the register table should be set to zero unless

specified otherwise (see Powerdown section).

DIGITAL FILTER CHARACTERISTICS

The DAC employ different digital filters. There are 4 types of digital filter, called Type 0, 1, 2 and 3.

The performance of Types 0 and 1 is listed in the table below, the responses of all filters is shown in

the proceeding pages.

PARAMETER

TEST CONDITIONS

MIN

TYP

MAX

UNIT

DAC Filter Type 0 (USB mode, 250fs operation)

+/- 0.03dB

0

0.416fs

Passband

-6dB

0.5fs

Passband Ripple

+/-0.03

dB

Stopband

0.584fs

Stopband Attenuation

f > 0.584fs

-50

dB

DAC Filter Type 1 (USB mode, 272fs or Normal mode operation)

+/- 0.03dB

0

0.4535fs

Passband

-6dB

0.5fs

Passband Ripple

+/- 0.03

dB

Stopband

0.5465fs

Stopband Attenuation

f > 0.5465fs

-50

dB

Table 20 Digital Filter Characteristics