SAA7806H NXP [NXP Semiconductors], SAA7806H Datasheet - Page 21

• Manufacturer Part Number: SAA7806H
• Description: One chip automotive CD audio device
• Manufacturer: NXP [NXP Semiconductors]

Philips Semiconductors
9397 750 13697
Objective data sheet
The integrate and dump block converts the incoming samples at the hf_clk frequency into
a stream of one sample per sysclk period. It averages a number of samples to achieve
this. If the division factor for the system clock is 2, 4, 8, 16, or 32, an average of 2, 4, 8, 16
or 32 incoming samples is taken and passed on further. The result is a gain in the number
of effective bits of the analog-to-digital conversion.
High-pass filter:
implemented. This can be used to filter the remaining DC jump on defects (analog HPF
will have filtered off most). The cut-off frequency of the digital high-pass filter can be
changed on the fly, by writing to register HighPassFiltCont.
It is possible to reset the state of the high-pass filter, via bit 6 of register HighPassFiltCont.
The input and the output of the high-pass filter is 8 bits wide.
The high-pass filter is implemented in a ’1 minus low pass’ structure. It is possible to hold
the low-pass filter on defects. For more information, see
page
The high-pass filter is driven by the system clock. Its bandwidth is also proportional to the
sysclk.
An approximate formula for the cut-off frequency, f
Peak detectors:
block.
The first type works on an immediate attack / slow decay basis, and is used for measuring
peaks, amplitude and offset for readback by software sending peak information to the
defect detector.
The second type works on the principle of detecting maximum and minimum peaks within
a window, and is used for the AGC and AOC control logic.
Both sets of peak detectors will look at the RF after it has passed an optional noise filter.
This noise filter is an LPF with a programmable high cut-off frequency. This bandwidth is
programmed via register PDBandwidth(NOISEFILTERBW) for the noise filter before the
peak detectors of AGC/AOC and measurement read back. The defect detector peak
detector has its own noise filter which is programmed via register
DefectDetPeakBW(NOISEFILTBW).
Peak detector with decay filter:
shown in
f
c HPF
25.
=
Figure
HPSet 5:0
-----------------------------
2
13.
2
There are 2 types of peak detectors present in the signal conditioning
A first order IIR high-pass filter with a variable 3 dB point is
11
Rev. 01 — 20 June 2005
f
sysclk
The functional schematic of this peak detection is
One chip automotive CD audio device
c
, of the high-pass filter is
Section “Defect Detector” on
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
SAA7806
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