ACS32201 datasheet(11/65 Pages) IDT

11 / 65 page

IDT CONFIDENTIAL

V0.6 07/11

ACS32201

LOW-POWER, HIGH-FIDELITY, CLASS-D AMPLIFIER

3.3.

Digital DAC Volume Control

The signal volume can be controlled digitally, across a gain and attenuation range of -95.25dB to 0dB (0.375dB steps).

The level of attenuation is specified by an eight-bit code, ‘DACVOL_x’, where ‘x’ is L, or R. The value “00000000” indi-

cates mute; other values select the number of 0.375dB steps above -95.625dB for the volume level.

3.4.

Parametric Equalizer

The ACS32201 has a dual 6-band digital parametric equalizer to enable fine tuning of the audio response and prefer-

ences for a given system. Each EQ may be enabled or disabled independently. Typically one EQ will be used for

speaker compensation and disabled when only headphones are in use while the other EQ is used to alter the audio to

make it more pleasing to the listener. This function operates on the digital audio data before it is converted back to ana-

log by the audio DACs.

In all, 186 bytes of memory are required to store the parameters for each equalizer: each filter requires 5, 24-bit coeffi-

cients. There are 6 filters per channel, requiring a total of 180 bytes of EQ coefficient RAM. Two additional 24-bit values

per channel store the prescale value, resulting in 372 bytes total, described later. Rather than having all 372 bytes be in

the I2C address space of the device, access to the EQ ram occurs through the Control/Status registers.

3.4.1.

Prescaler & Equalizer Filter

The Equalizer Filter consists of a Prescaler and 6 cascaded 6-tap IIR Filters. The Prescaler allows

the input to be attenuated prior to the EQ filters in case the EQ filters introduce gain, and would thus

clip if not prescaled.

IDT provides a tool to enable an audio designer to determine appropriate coefficients for the equal-

izer filters. The filters enable the implementation of a 6-band parametric equalizer with selectable fre-

quency bands, gain, and filter characteristics (high, low, or bandpass).

Figure 3. Prescaler & EQ Filters

Bit

Label

Type

Default

Description

R4 (04h)

Left DAC

Volume Control

7:0

DACVOL_L

[7:0]

(0dB)

Left DAC Volume Level

0000 0000 = Digital Mute

0000 0001 = -95.25dB

0000 0010 = -94.875dB

... 0.375dB steps up to

1111 1111 = 0dB

Note: If DACVOLU is set, this setting will take effect

after the next write to the Right Input Volume register.

R5 (05h)

Right DAC

Volume Control

7:0

DACVOL_R

[7:0]

(0dB)

Right DAC Digital Volume Level

0000 0000 = Digital Mute

0000 0001 = -95.25dB

0000 0010 = -94.875dB

... 0.375dB steps up to

1111 1111 = 0dB

Table 8. DAC Volume Control Registers

DATA IN

eq_prescale

Filter 0

DATA OUT

Filter 1

Filter 2

Filter 3

Filter 4

Filter 5

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