PCM1861 datasheet(23/115 Pages) TI

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CIC Filter

ADC

Auto

Gain

Control

Analog

PGA

Digital

PGA

Controller

Zero

Cross

Detector

Digital PGA

Overflow Detector

Decimation

Filter

Digital

Mixer

S-curve

Volume

Mixer

PGA

-12 dB to +32dB

0.5dB

+12 dB

-100dB ~ +18 dB

-100dB ~ 0 dB

PCM1861, PCM1863, PCM1865

www.ti.com

SLAS831C – MARCH 2014 – REVISED AUGUST 2014

Automatic Clipping Suppression (continued)

Figure 25. Sampling points within the PCM186x for Auto Clipping Suppression

Maximum Attenuation Level

This feature is not designed to be a complete analog gain control. This feature was defined to avoid clipping, and

to inform the system microcontroller of a clipping event, to allow the microcontroller (or the end user) to decide if

the gain should be increased again.

The maximum attenuation is programmable to be -3 / -4 / -5 / -6 dB.

Channel Linking

Depending on the application, users may not want to link input channels, however, for the majority of Stereo

input applications, its strongly recommended to set the system to track gain across inputs, to maintain balance.

The Auto PGA Clipping Suppression Control has the following settings:

Table 5. Auto Clipping Suppression Control Registers

Usage

Values

Location

0: Disable (Default)

AGC_EN

Pg0 0x05

Enable Auto Gain Control.

1: Enable

0: 80

Start auto gain control after detects CLIP_NUM times of

1: 40

CLIP_NUM[1:0]

Pg0 0x05

ADC sample clips

2: 20

3: 10 (Default)

0: -3dB (Default)

1: -4dB

MAX_ATT[1:0]

Pg0 0x05

Maximum automatic attenuation

2: -5dB

3: -6dB

Enable Clipping detection after the digital PGA. Note,

0: Disable (Default)

DPGA_CLIP_EN

Pg0 0x05

digital PGA is post ADC, meaning that there will be a short

1: Enable

delay before clipping is detected.

0: Independent control (Default)

Link all channels together. Should be linked if dealing with

LINK

Pg0 0x05

1: Ch1[R]/Ch2[L]/Ch2[R] follow Ch1[L]

stereo sources to maintain balance.

PGA value.

0: Immediate Change

SMOOTH

Pg0 0x05

Enable Smooth transition from step to step. (zero crossing)

1: Smooth Change (Default)

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Product Folder Links: PCM1861 PCM1863 PCM1865

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