SGTL5000XNAA3R2 Datasheet, PDF (22/68 Pages) Freescale Semiconductor, Inc – Low Power Stereo Codec with Headphone Amp

FUNCTIONAL DEVICE OPERATION
FUNCTIONAL INTERNAL BLOCK DESCRIPTION
H (z)

b₀  b₁z^1  b₂ z ^2
1 a₁z^1  a₂ z ^2
Direct Form1
X(z)

b0
z ^1
b₁
-a1
z ^1
H(z)X(z)
z ^1
z ^1
b₂
-a₂
Figure 15. 5-Coefficient Biquad Filter and Transfer Function
If a band is enabled but is not being used (flat response),
then a value of 0.5 should be put in b₀ and all other
coefficients should be set to 0.0. Note that the coefficients
must be converted to hex values before writing to the
registers. By default, all the filters are loaded with coefficients
to give a flat response.
In order to create EQ presets such as Rock, Speech,
Classical, etc, the coefficients must be calculated, converted
to 20-bit hex values and written to the registers. Note that
coefficients are sample-rate dependent and separate
coefficients must be generated for different sample rates.
Please contact Freescale for assistance with generating the
coefficients.
Refer to 7-Band PEQ Preset Selection for a programming
example that shows how load the filter coefficients when the
end-user changes the preset.
PEQ can be disabled (pass-through mode) by writing 0 to
DAP_AUDIO_EQ->EN bits.
5-Band Graphic EQ
The 5-band graphic equalizer is implemented using 5
parallel second order IIR filters. All filters are implemented
using biquad filters whose coefficients are programmed to set
the bands at a specific frequency. The GEQ bands are fixed
at 115 Hz, 330 Hz, 990 Hz, 3000 Hz, and 9900 Hz. The
volume on each band is independently adjustable in the
range of +12 dB to -11.75 dB in 0.25 dB steps.
Refer to 5-Band GEQ Volume Change for a programming
example that shows how to change the GEQ volume.
Tone Control
Tone control comprises treble and bass controls. The tone
control is implemented as one 2nd order low pass filter (bass)
and one 2nd order high pass filter (treble).
Refer to Tone Control - Bass and Treble Change for a
programming example that shows how to change Bass and
Treble values.
Automatic Volume Control (AVC)
An Automatic Volume Control (AVC) block is provided to
reduce loud signals and amplify low level signals for easier
listening. The AVC is designed to compress audio when the
measured level is above the programmed threshold or to
expand the audio to the programmed threshold when the
measured audio is below the threshold. The threshold level is
programmable with an allowed range of 0 to -96 dB.
Figure 16 shows the AVC block diagram and controls.
SGTL5000
22
Analog Integrated Circuit Device Data
Freescale Semiconductor