SI270X-A-EVB Silicon Laboratories Inc, SI270X-A-EVB Datasheet - Page 29

• Manufacturer Part Number: SI270X-A-EVB
• Description: BOARD EVAL FOR SI270X-A
• Manufacturer: Silicon Laboratories Inc

Specifications of SI270X-A-EVB

• Board Type: Fully Populated
• Amplifier Type: Class D
• Output Type: 2-Channel (Stereo) with Stereo Headphones
• Max Output Power X Channels @ Load: 5W x 2 @ 3 Ohm
• Voltage - Supply: 9V
• Utilized Ic / Part: SI270X-A
• Description/function: Audio Amplifiers
• Output Power: 5 W
• Product: Audio Modules
• For Use With/related Products: Si270x
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Operating Temperature: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant
• Other names: 336-1929

Si2704/05/06/07-A10
4.6.6. Dynamic Range Compression (Si2706/07 only)
The Si2706/07 features dynamic range compression (DRC) with programmable linear gain, compression
threshold, compression ratio, look ahead time, attack rate, and release rate.
DRC increases the net output power without clipping by decreasing the peak amplitudes of audio signals and
increasing the rms content of the lower amplitude audio signal. Audio signals below the threshold are increased by
the linear gain and audio signals above the threshold are compressed by a pre-defined compression ratio.
Figure 23 shows a plot of dynamic range compression audio processing with the DRC_THRESHOLD parameter
set at –40 dBFS, DRC_GAIN parameter at +20 dB relative to an uncompressed transfer function and
DRC_SLOPE set for a 2:1 compression ratio. For input signals below the compression threshold of –40 dBFS, the
output signal is increased by 20 dB relative to the input signal. For input signals above the compression threshold
the input signal is increased by 1 dB for every 2 dB increase in audio input level.
Figure 23. Dynamic Range Compression Example
In this example, the input dynamic range of 90 dB is reduced to an output dynamic range of 70 dB.
Figure 24 shows the time domain response of the dynamic range compression. The DRC_ATTACK_TIME
parameter sets how quickly the gain compression responds to changes in the input level, and the
DRC_RELEASE_TIME parameter sets how quickly the gain compression returns to linear gain once the audio
input level drops below the compression threshold.
DRC_LOOKAHEAD_TIME allows setting the look ahead time that permits the DRC circuit to adjust the
compression to sudden level changes thus preventing the clipping of the fast changing signal. Refer to “AN503:
Si270x Class-D Amplifier—Dynamic Range Compressor Use” for additional information.
Rev. 0.6
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