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Datasheet - D e ta i l e d D e s c r i p t i o n

Figure 29. Audio controlled LED digital processing internal circuit

These three output channels (ch1, ch2, ch3) can be routed to any of the current sources according to Figure 28.

The input amplitude is mapped into different colors (Look Up Table in Figure 29) for RGB LED(s) or brightness for sin-

gle color LED(s). The mapping is controlled by the register audio_color. If audio_color = 000, then the mapping is done

as follows:

Very low amplitudes are mapped to black, for higher amplitudes, the color smoothly transitions from blue, green, cyan,

yellow, red and eventually to white (for high input amplitudes).

8.8.1 AGC

The AGC is used to ‘compress’ the input signal and to attenuate very low input amplitude signals (this is performed to

ensure no light output for low signals especially for noisy input signals).

The AGC monitors the input signal amplitude and filters this amplitude with a filter with a short attack time, but a long

decay time (decay time depends on the register agc_ctrl). This amplitude measurement (represented by an integer

value from 0 to 15) is then used to amplify or attenuate the input signal with one of the following amplification ratios

(output to input ratio) – the curve A, B, or C is selected depending on the register agc_ctrl:

Figure 30. AGC curve A (x-axis: input amplitude, y-axis: output amplitude; actual value: gain between output to

input)

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AS3676

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