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

AN259REV2

JAN ‘09

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

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

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

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