cxa1897q Sony Electronics, cxa1897q Datasheet - Page 17

• Manufacturer Part Number: cxa1897q
• Description: Dolby B Type Noise Reduction System With Recording/playback Equalizer
• Manufacturer: Sony Electronics

2. AMS
(1) AMS output logic
(2) AMS level setting
With the reference output level (–25dBm) of the playback equalizer as 0dB, consider at how many decibels the
AMS level is to be set.
(3) AMS band setting
By inserting a capacitor in series with the external resistor determined in (2), the direct current of the AMS is
cut off. The lower end of the AMS band can be limited by adjusting the capacitor value because the cut-off
frequency of the high-pass filter is determined by this external resistor and capacitor.
Detection status
AMS OUT
Inside of IC
{
Use formula 1 to determine external resistance R.
Ex. 1) To set the detection level at 20dB lower than the reference (calculated on the assumption that
Ex. 2) To set the detection level at 30dB lower than the reference,
R=
Vpeak (PBOUT1)+Vpeak (PBOUT2)
Vpeak (PBOUT1)+Vpeak (PBOUT2)
1ch=2ch)
–25dBm–20dB=–45dBm=6.16mVpeak
R=6.16 10
In which case, external resistance R is 6.2k .
–25dBm–30dB=–55dBm=1.95mVpeak
R=1.95 10
In which case, external resistance R is 2k .
R (external resistance)
Signal detected
36
2
1
3
–3
–3
2
AMS OUT
10
10
L
6
6
6.2k
2k
No signal detected
Vcc
GND
}
H
Compare
—17—
10
5 5µA
When the pins have been connected as shown on the
left figure,
Low : Approximately 0.3V (V
High : Vcc (V)
6
— 1
CE
(sat) voltage)
CXA1897Q