lp5527tlx National Semiconductor Corporation, lp5527tlx Datasheet - Page 13

• Manufacturer Part Number: lp5527tlx
• Description: Tiny Led Driver For Camera Flash And 4 Leds With I2c Programmability, Connectivity Test And Audio Synchronization
• Manufacturer: National Semiconductor Corporation

Audio Synchronization
The LED1 output can be synchronized to incoming audio
signal with Audio Synchronization feature. Audio Synchroni-
zation synchronizes LED1 based on input signal’s peak am-
plitude. Programmable gain and automatic gain control func-
tion are also available for adjustment of input signal
amplitude to light response. Control of LED1 brightness
refreshing frequency is done with four different frequency
configurations. The digitized input signal has a DC compo-
nent that is removed by a digital DC-remover. The DC-
remover is a high-pass filter where corner frequency is user
selectable by using DC_FREQ bit. LP5527 has 2-channel
audio (stereo) input for audio synchronization, as shown in
the figure below. The inputs accept signals in the range of 0V
to 1.6V peak-to-peak and these signals are mixed into a
single wave so that they can be filtered simultaneously.
Audio Synchronization Input Electrical Parameters
CONTROL OF AUDIO SYNCHRONIZATION
The following table describes the controls required for audio synchronization. LED1 brightness control through serial interface is
not available when audio synchronization is enabled.
Audio Synchronization Control
EN_SYNC
EN_AGC
GAIN_SEL[2:0]
SPEED_CTRL[1:0]
THRESHOLD[3:0]
DC_FREQ
Symbol
Z
A
IN
IN
Parameter
Input Impedance of
ASE1, ASE2
ASE1, ASE2 Audio
Input Level Range
(peak-to-peak)
Audio synchronization enabled. Set EN_SYNC = 1 to enable audio synchronization or 0 to disable.
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 -46 dB.
Control for refreshing frequency. Sets the typical refreshing rate for the LED1 output.
Control for the audio input threshold. Sets the typical threshold for the audio inputs signals.
May be needed if there is noise on the audio lines.
Control for the high-pass filter corner frequency.
0 = 80 Hz
1 = 510 Hz
Conditions
Min input level needs maximum gain;
Max input level for minimum gain.
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LP5527 audio synchronization is mainly done digitally and it
consists following signal path blocks (see figure below).
Automatic Gain Control (AGC) adjusts the input signal to
suitable range automatically. User can disable AGC and the
gain can be set manually with programmable gain. Audio
synchronization is based on peak detection method.
• Input buffer
• AD converter
• Automatic Gain Control (AGC) and manually program-
• Peak detector
mable gain
Min
10
0
Typ
15
Max
1600
20184016
Units
www.national.com
mV
kΩ