SAA7806H NXP [NXP Semiconductors], SAA7806H Datasheet - Page 22

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

Philips Semiconductors
9397 750 13697
Objective data sheet
The minimum and maximum peaks of the incoming signal are measured. Switch S1 takes
the largest value at its inputs. Switch S2 takes the minimum value at its inputs. The time
constant of the decay filters has to be long. The same bandwidth is used for the decay
filters of both the minimum and maximum peak detectors. The decay filter for the
maximum peak responds to the smallest value possible. The decay filter for the minimum
peak responds to the largest value possible.
The decay bandwidth of the measurement readback decay filter is controlled via register
PDBandwidth(DECAYBW), the bandwidth of the defect detector is controlled via register
DefectDetPeakBW(DECAYBW).
The following settings of the decay filters are possible: C = 1
m = DECAYBW[3:0] + 6.
The corresponding bandwidths of the decay filter are shown in
frequency of the system clock is 10 MHz.
Table 4:
Peak detector based on window:
shown in
m
6
7
8
9
Fig 13. Peak detection diagram with decay filter
Fig 14. Peak detection diagram with window
t ( s)
6.35
12.75
25.55
51.15
Figure
Time constants of the decay filters, at sysclk = 10 MHz
14.
HF_in
m
10
11
12
13
HF_in
Rev. 01 — 20 June 2005
t ( s)
102.4
204.7
409.6
819.2
noise filter
noise filter
The functional schematic of this peak detection is
0
m
14
15
16
17
S1
S2
C
C
One chip automotive CD audio device
t (ms)
1.64
3.28
6.55
13.11
window width
maxpeak
minpeak
© Koninklijke Philips Electronics N.V. 2005. All rights reserved.
001aab758
001aab757
maxpeak
minpeak
2
Table
m
, for m = 6 to 21, where
m
18
19
20
21
4, when the
SAA7806
t (ms)
26.21
52.43
104.8
209.7
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