Cirrus Logic AN259 User Manual

AN259

Transitioning from the CS4382 to the CS4382A or CS4385

1. Introduction

This application note describes how to transition easily to the CS4385 or CS4382A from an existing
design which uses the CS4382. The CS4382A was designed to give a simple upgrade path from the
CS4382 whereas the CS4385 adds some additional features. Please refer to the CS4382A and CS43 85
data sheets for supplemental information and specifications concerning operation of the device. A brief
comparison between the product families is shown in Table 1.

1.1 What the CS4382A offers over the CS4382:

• Sixth order multi-bit delta-sigma modulator for lower out of band noise

• Increased full-scale output level for ease of board level noise management

• Improved lower latency PCM digital filter

• Non-decimating DSD processor with on chip 50 kHz filtering

• Uses identical register mapping

1.2 Changes from the CS4382 that the CS4382A requires:

• The VD supply must be changed to 2.5 V from either the 3.3 V or 5 V of the CS4382

•

Depending on the desired output voltage require ments, attenuation may need to be added to the off-chip filter.

• Loss of simultaneous support for two synchronous sample rates mode which was available in the CS43 82.
This mode provided for dual sample rates such as

DVD audio and required the use of

LRCK2 and SCLK2. This mode is not offered in the CS4382A or

CS4385.

• Additional resistors on MUTEC pins

192 kHz front channels with 96 kHz surrounds for

1.3 What the CS4385 offers over the CS4382A:

• Additional DSD functions of Volume control, Mute pattern detect, support for phase modulation mode, and

offers a direct to switched capacitor path.

• 1/2 dB volume control steps (vs. 1 dB in CS4382/82A)

• One-Line and TDM modes

• Auto-mute polarity detection

• Auto-speed mode detection

1.4 Changes from the CS4382 that the CS4385 requires:

• The VD supply must be changed to 2.5 V from the either 3.3 V or 5 V of the CS4382

•

Depending on the desired output voltage requirements, attenuation may need to be added to the off-chip filter.

• Simultaneous support for two synchronous sample rates is no longer available

• Additional resistors on MUTEC pins

• 4 pins change location or function for hardware mode. The changes aren't necessary for software mode.

• Requires different register mapping from the CS4382

http://www.cirrus.com

Copyright © Cirrus Logic, Inc. 2009

(All Rights Reserved)

AN259REV2

JAN ‘09

1

AN259

CS4385 CS4382A CS4382
Dynamic Range
THD+N
Resolution
Sample Rate
Pow er Suppl y

Volume Control 0.5 dB
Auto F s De tect Yes
Package 48-LQFP

Table 1. Product Comparison

dB
dB

bits

kHz

VA
VD

114

-100
24

192

5

2.5

For users of the CS4382, the CS4385 is a simple, yet affordable, upgrade to a richer feature set and lower
out-of-band noise performance.

2. The Design Transition

2.1 Transitioning from the CS4382 to CS4382A

2.1.1 Hardware changes

114 114

-100 -100
24 24

192 192

55

2.5 3.3 to 5

1 dB 1 dB

No No

48-LQFP 48-LQFP

The CS4382A pinout was primarily based on the CS4382 with only 2 pins changing function. Other
pins have new recommended components but the circuit topologies remain the same and thu s do n ot
require modification to the PCB. The most significant change is that the VD core of the CS4382A
requires 2.5 V for operation, whereas the CS4382 was able to run from 3.3 V to 5 V. The CS4382A will
NOT operate off of a VD supply of 3.3 V or 5 V.

Figure 1 and Figure 2 show the CS4382 and CS4382A pinouts respectively. The changes to the two
pinouts are highlighted. Figure 1 highlights the pins which have changed function and which may
require a PCB change. Figure 2 highlights the pins which have new recommended components.

2 AN259REV2

AN259

AOUTA1-

AOUTA1+

VQ

MUTEC234

AOUTB1+

AOUTB4-

AOUTB1-

36

AOUTA2-

35

AOUTA2+
AOUTB2+

34
33

AOUTB2-

32

VA

31

GND

AOUTA3-

30

AOUTA3+

29

AOUTB3+

28
27

AOUTB3-

AOUTA4-

26

AOUTA4+

25

AOUTB4+

DSDA2
DSDB1
DSDA1

VD

GND
MCLK

LRCK1(DSD_EN)

SDIN1

SCLK1

LRCK2

SDIN2

SCLK2

MUTEC1

AOUTA1-

VLS

M3(DSD_SCLK)

DSDB4

DSDB3

DSDA4

DSDB2

DSDA3

48 47 46 45 44 43 42 41 40 39 38 37

1

2

3

4

5

6

7

8

9

10

11

12

13 14 15 16 17 18 19 20 21 22 23 24

SDIN3

= denotes location or function changes

when trasitioning to CS4382A

SDIN4

CS4382

M1(SDA/CDIN)

M2(SCL/CCLK)

VQ

RST

VLC

FILT+

M0(AD0/CS)

Figure 1. CS4382 pinout

AOUTA1+

MUTEC234

AOUTB1-

AOUTB1+

36

AOUTA2-

35

AOUTA2+
AOUTB2+

34

33

AOUTB2-

32

VA

31

GND

AOUTA3-

30

AOUTA3+

29

AOUTB3+

28

27

AOUTB3-

AOUTA4-

26

AOUTA4+

25

AOUTB4-

AOUTB4+

DSDA2
DSDB1
DSDA1

VD

GND
MCLK

LRCK1(DSD_EN)

SDIN1

SCLK1

TST

SDIN2

TST

1
2
3
4
5
6
7
8
9
10
11
12

= denotes pins which require changes

DSDB3

DSDA4

DSDB2

DSDA3

48 47 46 45 44 43 42 41 40 39 38 37

CS4382A

13 14 15 16 17 18 19 20 21 22 23 24

SDIN4

SDIN3

M1(SDA/CDIN)

M2(SCL/CCLK)

to components or voltages

VLS

DSDB4

VLC

M0(AD0/CS)

MUTEC1

M3(DSD_SCLK)

RST

FILT+

Figure 2. CS4382A pinout

Location or function changes as denoted in Figure 1 are as follows:

• The CS4385 does not support the simultaneous synchronous sample rate function of the CS4382. Pins 10
and 12 are now Test inputs.

Pins which require changes to external components or voltages as denoted in Figure 2 are as follows:

• Pin 4 (VD) requires 2.5 V for recommended operation. The CS4382 used either 3.3 V or 5 V, which, if left
unchanged, would damage the CS4382A.

• Pin 22 (MUTEC234) and pin 41 (MUTEC1) require an additional pull-up or down in order to mute during
reset. While reset is asserted these pins are high impedance and will not drive the mute circuitry. It is
recommended that the pull-up/down resistance properly biases the off-chip mute circuit into muting.

• Pins 23 - 30, 33 - 40 (AOUTs) have a new recommended filter circuit. This filter uses the same filter topology
as the CS4382. The component values have been changed to account for the extra output level from the
CS4382A and still provide 2 Vrms on the output. A general optimization was also made in order to reduce
the thermal noise contribution of the resistances (using smaller resistances where possible). Please refer to
the CS4382A datasheet for details on the new recommended filter.

2.1.2 Functional changes

- With the addition of the non-decimating DSD processor mode comes the added benefits of

matched PCM and DSD output levels and an on chip 50 kHz filter.

- The CS4382A uses a new multi-bit Delta-Sigma modulator core with mis-match shaping which al-

lows for lower over-all out-of-band noise and improved audio quality.

- The CS4382A gained new digital filters with improved stop-band performance and lower latency.

- The full scale differential output voltage has increased which needs to be accounted for in the an-

AN259REV2 3

AN259

alog filter gain (if similar output level to the CS4382 is desired).

- The mute control pins are high impedance while reset is asserted. An external pull-up or down is
required to properly bias the off-chip mute circuit into muting during reset.

- The dual serial port function of the CS4382 which accepted two simultaneous synchronous sam­ple rates (such as 192 kHz front and 96 kHz surrounds) is not supported.

2.2 Transitioning from the CS4382 to CS4385

2.2.1 Hardware changes

The CS4385 pinout was primarily based on the CS4382 with only 3 pins changing function. Other pins
have new recommended components but the circuit topologies remain the same and thus do not
require modification to the PCB. The most significant change is that the VD core of the CS4385
requires 2.5 V for operation, whereas the CS4382 was able to run from 3.3 V to 5 V. The CS4385 will
NOT operate off of a VD supply of 3.3 V or 5 V.

Figure 3 and Figure 4 show the CS4382 and CS4385 pinouts respectively. The changes to the two
pinouts are highlighted. Figure 3 highlights the pins which have changed function and which may
require a PCB change. Figure 4 highlights the pins which have new recommended components.

AOUTB1+

AOUTA1+

MUTEC234

AOUTB1-

36

35

34

33

32

31

30

29

28

27

26

25

AOUTB4-

AOUTB4+

AOUTA2­AOUTA2+
AOUTB2+
AOUTB2­VA

GND

AOUTA3­AOUTA3+
AOUTB3+
AOUTB3­AOUTA4-

AOUTA4+

DSDA2
DSDB1
DSDA1

VD

GND
MCLK

LRCK1(DSD_EN)

SDIN1
SCLK1
LRCK2

SDIN2
SCLK2

MUTEC1

AOUTA1-

VLS

M3(DSD_SCLK)

DSDB4

DSDA4

DSDB3

DSDB2

DSDA3

48 47 46 45 44 4 3 42 41 40 39 38 37

1

2

3

4

5

6

7

8

9

10

11

12

13 14 15 16 17 1 8 19 20 21 22 23 24

SDIN3

= denotes location or function changes

when trasitioning to CS4385

SDIN4

CS4382

M1(SDA/CDIN)

M2(SCL/CCLK)

VQ

RST

VLC

FILT+

M0(AD0/CS)

Figure 3. CS4382 pinout

AOUTA1+

MUTEC234

AOUTA1-

VLS

DSDB3

DSDA3

AOUTB1-

AOUTB1+

36

AOUTA2­AOUTA2+

35

AOUTB2+

34

AOUTB2-

33

32

VA

31

GND

AOUTA3-

30

AOUTA3+

29

AOUTB3+

28

27

AOUTB3-

AOUTA4-

26

AOUTA4+

25

AOUTB4-

AOUTB4+

DSDA2

DSDB1
DSDA1

VD

GND

MCLK

LRCK
SDIN1
SCLK

M4

SDIN2

M3

DSDB2

48 47 46 45 44 43 42 41 40 39 38 37

1

2

3

4

5

6

7

8

9

10

11

2

1

13 14 15 16 17 18 19 20 21 22 23 24

SDIN3

DSDA4

CS4385

SDIN4

M1(SDA/CDIN)

M2(SCL/CCLK)

= denotes pins which require changes

to components or voltages

MUTEC1

DSDB4

DSD_SCLK

VQ

VLC

RST

FILT+

M0(AD0/CS)

Figure 4. CS4385 pinout

Location or function changes as denoted in Figure 3 are as follows:

• Pin 7 is no longer DSD_EN in hardware mode. In order to enter DSD mode on the CS438 5 you mu st either
set the M4 and M3 pins accordingly or use SPI™ or I

• The CS4385 does not support the simultaneous synchronous sample rate function of the CS4382. Pins 10
and 12 are now dedicated for stand-alone configuration (voltage input on these pins are still referenced to
VLS).

• Pin 42 no longer functions as M3 in stand-alone PCM modes. It is now a dedicated DSD_SCLK pin.

4 AN259REV2

2

C configuration.

AN259

Pins which require changes to external components or voltages as denoted in Figure 4 are as follows:

• Pin 4 (VD) requires 2.5 V for recommended operation. The CS4382 used either 3.3 V or 5 V, which, if left

unchanged, would damage the CS4385.

• Pin 22 (MUTEC234) and pin 41 (MUTEC1) require an additional pull-up or down in order to indicate the

desired direction of mute polarity. While reset is asserted these pins are high impedance and will not drive
the mute circuitry. It is recommended that the pull-up/down resistance properly biases the off-chip mute
circuit into muting.

• Pins 23 - 30, 33 - 40 (AOUTs) have a new recommended filter circuit. This filter uses the same filter topology

as the CS4382. The component values have been changed to account for the extra output level from the
CS4385 and still provide 2 Vrms on the output. A general optimization was also made in order to reduce the
thermal noise contribution of the resistances (using smaller resistances where possible). Please refer to the
CS4385 datasheet for details on the new recommended filter.

2.2.2 Functional changes

- The CS4385 uses a new register mapping in order to accommodate the additio nal features which
it provides over the CS4382. Please refer to the CS4385 datasheet for the new mapping.

- With the addition of the non-decimating DSD processor mode comes the added benefits of
matched PCM and DSD output levels, DSD volume control, an on chip 50 kHz filter, Phase Mod­ulation input mode, and DSD mute pattern detection. A direct DSD path to the switched capacitor
array is also offered. All of the features are accessed through the configuration registers.

- The CS4385 supports a setting for auto-selection of the speed mode to set what sample rate range
the DAC is to expect. This allows the CS4385 to operate at sample rates from 4 kHz on up to
192 kHz without intervention (Note: there are a few reserved frequencies, see datasheet for de­tails). This setting is available in both stand-alone and control-port operation.

- The volume control in the CS4385 offers 0.5 dB step sizes for more volume setting resolution.

- The CS4385 offers TDM and One-Line modes for compatibility with various multi-channel sur­round sound DSPs which helps reduce board real-estate from the additional data lines. These
modes are not available in stand-alone mode.

- The CS4385 uses a new multi-bit Delta-Sigma modulator core with mis-match shaping which al­lows for lower over-all out-of-band noise and improved audio quality.

- The CS4385 gained new digital filters with improved stop-band performance and lower latency.

- The full scale differential output voltage has increased which needs to be accounted for in the an­alog filter gain (if similar output level to the CS4382 is desired).

- The mute control pins now support auto polarity detection. This allows for selection of active high
or low mute circuitry without the need to set registers. An external pull-up or down is required to
set the mute polarity.

- The MCLK divide by 2 bit is no longer necessary to access the 1024x MCLK/LRCK ratio (SSM),
512x MCLK/LRCK ratio (DSM) and 256x MCLK/LRCK ratio. A new ratio of 1152x has been added
for 32 kHz operation.

- The dual serial port function of the CS4382 which accepted two simultaneous synchronous sam­ple rates (such as 192 kHz front and 96 kHz surrounds) is not supported.

AN259REV2 5

AN259

Table 2. Revision History

Release Date Changes

REV1 JAN 2005 Initial Release
REV2 JAN 2009 Added text to indicate MUTEC pins of the CS4382A are high impedance

during reset

Contacting Cirrus Logic Support

For a complete listing of Direct Sales, Distributor, and Sales Representative contacts, visit the Cirrus Logic web site at:

http://www.cirrus.com

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6 AN259REV2