LP55281TL/NOPB National Semiconductor, LP55281TL/NOPB Datasheet - Page 15

• Manufacturer Part Number: LP55281TL/NOPB
• Description: IC LED DRIVER RGB 36-USMD
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: RGB LED Driverr

Specifications of LP55281TL/NOPB

• Constant Current: Yes
• Topology: PWM, Step-Up (Boost)
• Number Of Outputs: 12
• Internal Driver: Yes
• Type - Primary: Light Management Unit (LMU)
• Type - Secondary: Color, RGB
• Frequency: 1MHz ~ 2MHz
• Voltage - Supply: 3 V ~ 5.5 V
• Voltage - Output: 4 V ~ 5.3 V
• Mounting Type: Surface Mount
• Package / Case: 36-MicroSMD
• Operating Temperature: -30°C ~ 85°C
• Current - Output / Channel: 300mA
• Internal Switch(s): Yes
• Efficiency: 88%
• For Use With: LP55281RLEV - BOARD EVAL FOR LP5528 RGB DRIVER
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LP55281TLTR

Audio Synchronization
The ALED output can be synchronized to incoming audio with
Audio Synchronization feature. Audio Synch synchronizes
ALED based on input signal's peak amplitude. Programmable
gain and automatic gain control function are also available for
adjustment of input signal amplitude to light response. Control
of ALED brightness refreshing frequency is done with four
different frequency configurations. The digitized input signal
has DC component that is removed by a digital dc-remover
(-3 dB @ 500 Hz). LP55281 has a 2-channel audio (stereo)
input for audio synchronization, as shown in the figure below.
CONTROL OF AUDIO SYNCHRONIZATION
The following table describes the controls required for audio
synchronization. ALED brightness control through serial in-
GAIN_SEL
[2:0]
DC_FREQ
EN_AGC
EN_SYNC
SPEED_CTRL
[1:0]
THRESHOLD
[3:0]
THRESHOLD[3:0]
Audio Input Threshold Setting (Register 0Eh)
0000
0001
0010
1110
1111
...
Register
0Dh
Bits 7-5
Register
0Dh
Bit 4
Register
0Dh
Bits 3
Register
0Dh
Bits 2
Register
0Dh
Bits 1-0
Register
0Eh
Bits 3-0
Threshold Level, mV (typical)
Input signal gain control. Gain has a range from 0 dB to -46 dB.
[000] = 0 dB, [001] = -6 dB, [010] = -12 dB, [011] = -18 dB,
[100] = -24 dB, [101] = -31 dB, [110] = -37 dB, [111] = -46 dB
Control of the high-pass filter's corner frequency:
0 = 80 Hz
1 = 510 Hz
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.
Audio synchronization enabled. Set EN_SYNC = 1 to enable audio synchronization or 0 to disable.
Control for refreshing frequency. Sets the typical refreshing rate for the ALED output
[00] = FASTEST, [01] = 15 Hz, [10] = 7.6 Hz, [11] = 3.8 Hz
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.
Audio Synchronization Control (Registers 0Dh and 0Eh)
Disabled
0.2
0.4
2.5
2.7
...
15
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.
LP55281 audio synchronization is mainly realized digitally
and it consists following signal path blocks (see figure below)
•
•
•
•
terface is not available when audio synchronization is en-
abled.
Input buffer
AD converter
Automatic Gain Control (AGC) and manually
programmable gain
Peak detector
Audio Input Amplitude mV
Typical Gain Values vs Audio Input Amplitude
20 to 1600
10 to 800
3 to 170
5 to 400
0 to 10
0 to 20
0 to 40
1 to 85
P-P
Gain Value dB
20201119
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-12
-18
-24
-31
-37
-46
-6
0