LP3950 datasheet(21/31 Pages) NSC

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Audio Synchronization (Continued)

Audio Synchronization Characteristics

Symbol

Parameter

Conditions

Min

Typ

Max

Units

Zin

Input Impedance of AD1, AD2,

ASE pins

200

500

Ω

IN_SINGLE

Audio Input Level Range

(peak-to-peak), Single Ended

Audio

0.1

DDA −0.1

IN_DIFF

Audio Input Level Range

(peak-to-peak), Differential

Audio

0.1

DDA −0.1

3dB

Crossover Frequencies (−3 dB)

kHz

Narrow Frequency Response

Low Pass

Band Pass

High Pass

0.5

1.0 and 1.5

2.0

Wide Frequency Response

Low Pass

Band Pass

High Pass

1.0

2.0 and 3.0

4.0

CONTROL OF AUDIO SYNCHRONIZATION

The following table describes the controls required for audio

synchronization. Note that these controls are functional

when using serial interface (I

2C or SPI) for device control.

Also LP3950 audio synchronization functionality is illustrated

in Figure 18.

Audio Synchronization Control

EN_SYNC

Audio synchronization enabled. Set EN_SYNC=1to enable audio synchronization or 0

to disable.

SYNC_MODE

Synchronization mode selector. Set SYNC_MODE = 0 for amplitude synchronization. Set

SYNC_MODE = 1 for frequency synchronization.

MODE_CTRL[1:0]

See below: Mode control

EN_AGC

Automatic gain control. Set EN_AGC=1to enable automatic control or 0 to disable.

When EN_AGC is disabled, the audio input signal gain value is defined by GAIN_SEL.

GAIN_SEL[2:0]

Input signal gain control. Gain has a range from 0 dB to 21 dB with 3 dB steps:

[000] ... 0 dB

[011] ... 9 dB

[110] ... 18 dB

[001] ... 3 dB

[100] ... 12 dB

[111] ... 21 dB

[010] ... 6 dB

[101] ... 15 dB

INPUT_SEL[1:0]

[00] ... Single ended input signal, ASE.

[01] ... Differential input signal, AD1 and AD2.

[10] ... Stereo input or single ended and differential input signal.

Note: Sum of input signals divided by 2.

[11] ... No input

Please see Figure 15 for wiring.

SPEED_CTRL[1:0]

Control for speed of the mapping. Sets the reaction speed (or "sampling rate") for the

audio input signal:

[00] ... FASTEST

[01] ... FAST

[10] ... MEDIUM

[11] ... SLOW

In the amplitude mode f

MAX = 3.8 Hz, in the frequency mode fMAX = 7.6 Hz.

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