LP3954TLSLASHNOPB datasheet(19/60 Pages) TI1

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COMMAND 1

COMMAND 2

COMMAND 3

IF 0000 0000 and 0000 0000 then

Æ STOP

LOOP=0

start

stop

ADDRESS 50H

ADDRESS 51H

ADDRESS 52H

ADDRESS 55H

ADDRESS 54H

ADDRESS 53H

LP3954

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SNVS340D – JUNE 2005 – REVISED MARCH 2013

SINGLE PROGRAM

If control bit LOOP=0 the program will start from Command 1 and run to either last command or to empty “0000

0000 / 0000 0000” command.

The LEDs maintain the brightness of the last command when the single program stops. Changes in command

effective.

START BIT

Pattern_gen_ctrl register’s RGB_START bit will enable command execution starting from Command 1.

Pattern gen ctrl register (11H)

0 – Pattern generator disabled

rgb_start

Bit 2

1 – execution pattern starting from command 1

0 – pattern generator loop disabled (single pattern)

loop

Bit 1

1 – pattern generator loop enabled (execute until stopped)

0 – color intensity mode 0

log

Bit 0

1 – color intensity mode 1

HARDWARE ON/OFF CONTROL AND DIMMING

PWM_LED input can be used as direct ON/OFF control or PWM dimming control for selected RGB outputs or

the WLED groups. PWM_LED control can be enabled with the control bits in the Ext. PWM Control register.

Audio Synchronization

The color LEDs connected to RGB outputs can be synchronized to incoming audio with Audio Synchronization

feature. Audio Sync has 2 modes. Amplitude mode synchronizes color LEDs based on input signal’s peak

amplitude. In the amplitude mode the user can select between 3 different amplitude mapping modes and 4

different speed configurations. The frequency mode synchronizes the color LEDs based on bass, middle and

treble amplitudes (= low pass, band pass and high pass filters). User can select between 2 different frequency

responses and 4 different speed configurations for best audio-visual user experience. Programmable gain and

AGC function are also available for adjustment of input signal amplitude to light response. The Audio Sync

functionality is described more closely below.

USING A DIGITAL PWM AUDIO SIGNAL AS AN AUDIO SYNCHRONIZATION SOURCE

If the input signal is a PWM signal, use a first or second order low pass filter to convert the digital PWM audio

signal into an analog waveform. There are two parameters that need to be known to get the filter to work

successfully: frequency of the PWM signal and the voltage level of the PWM signal. Suggested cut-off frequency

(-3dB) should be around 2 kHz to 4 kHz and the stop-band attenuation at sampling frequency should be around -

48dB or better. Use a resistor divider to reduce the digital signal amplitude to meet the specification of the analog

audio input. Because a low-order low-pass filter attenuates the high-frequency components from audio signal,

MODE_CONTROL=[01] selection is recommended when frequency synchronization mode is enabled.

Application example 5 shows an example of a second order RC-filter for 29 kHz PWM signal with 3.3V

amplitude. Active filters, such as a Sallen-Key filter, may also be applied. An active filter gives better stop-band

attenuation and cut-off frequency can be higher than for a RC-filter.

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