LP3950 Datasheet, PDF (22/31 Pages) National Semiconductor (TI) – Color LED Driver with Audio Synchronizer

Audio Synchronization (Continued)
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FIGURE 18. LP3950 Audio Synchronization Functionality
MODE CONTROL IN THE FREQUENCY MODE
During the frequency mode (SYNC_MODE = 1) the user can
select between two filter options by MODE_CTRL[1:0] as
shown below (Figure 19). User can select the filters based
on the music type and light effect requirements. Filter op-
tions: Left figure, wide frequency response;
MODE_CTRL[1:0] is set to [00], [10] or [11]. Right figure,
narrow frequency response: MODE_CTRL[1:0] set to [01].
Signal passed through the lowpass filter is used to control
the duty cycle of red LEDs (R1 and/or R2 PWM outputs), the
signal passed through the bandpass filter is used to control
green LEDs (G1 and/or G2 PWM outputs) and high pass
signal controls blue LEDs (B1 and/or B2 PWM outputs).
Finally, the user can select the desired mapping speed by
SPEED_CTRL[1:0]. Of course, the user can connect any
color LED to any output in his/her own application (i.e. the
red output does not need to drive a red LED). Maximum duty
cycle is A100% as in the Flash mode (not 33% as in the
normal mode of the pattern generator, which is described in
Table RGB LED PWM Control ).
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FIGURE 19. Cross-over Frequencies. Left: Wide Frequency Response. Right: Narrow Frequency Response
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