Cirrus Logic AN259 - Manual (Page 5)

AN259
AN259REV2 5
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 additional 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 Mod-
ulation 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 de-
tails). 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 sur-
round 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 al-
lows 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 an-
alog 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 sam-
ple rates (such as 192 kHz front and 96 kHz surrounds) is not supported.