LP3950 Datasheet, PDF (21/31 Pages) National Semiconductor (TI) – Color LED Driver with Audio Synchronizer

Audio Synchronization (Continued)
Symbol
Zin
A_{IN_SINGLE}
A_{IN_DIFF}
f_{3 dB}
Audio Synchronization Characteristics
Parameter
Conditions
Min
Input Impedance of AD1, AD2,
200
ASE pins
Audio Input Level Range
(peak-to-peak), Single Ended
0.1
Audio
Audio Input Level Range
(peak-to-peak), Differential
0.1
Audio
Crossover Frequencies (−3 dB)
Narrow Frequency Response
Low Pass
Band Pass
High Pass
Wide Frequency Response
Low Pass
Band Pass
High Pass
Typ
Max
Units
500
kΩ
V_DDA −0.1
V
V_DDA −0.1
V
0.5
1.0 and 1.5
2.0
kHz
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 (I²C or SPI) for device control.
Also LP3950 audio synchronization functionality is illustrated
in Figure 18.
Audio Synchronization Control
EN_SYNC
SYNC_MODE
MODE_CTRL[1:0]
EN_AGC
GAIN_SEL[2:0]
INPUT_SEL[1:0]
SPEED_CTRL[1:0]
Audio synchronization enabled. Set EN_SYNC = 1 to enable audio synchronization or 0
to disable.
Synchronization mode selector. Set SYNC_MODE = 0 for amplitude synchronization. Set
SYNC_MODE = 1 for frequency synchronization.
See below: Mode control
Automatic gain control. Set EN_AGC = 1 to enable automatic control or 0 to disable.
When EN_AGC is disabled, the audio input signal gain value is defined by GAIN_SEL.
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
[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.
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 f_MAX = 7.6 Hz.
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