CXA1878Q
10. AMS circuit
DVCC
The CXA1878Q has the music sensor circuit.
R3
C3
AMS TC
37
AMS OUT
36
COMP
1kΩ
0dB
NR PBIN1
NR PBIN2
62
54
OP AMP WINDOW
COMP
0dB
16kHz
LPF
100kΩ
G1
G2
R2
R1
[ 2]
[ 1]
C1
[ 1]
C2
[ 2]
Fig. 4. AMS circuit block diagram
(1) AMS ON operation
The signal input from PB NR IN first passes through the LPF, then through the HPF/sensitivity setting
amplifier, and then through the WINDOW comparator where it is formed into a pulse wave. (See Fig. 5)
This signal which has been formed into a pulse wave is integrated by a capacitor connected to the AMS TC
pin (Pin 37) and then input to the comparator. (See Fig. 6)
AMS OUT turns ON when the AMS TC pin voltage falls below the comparator threshold value.
(When the sensitivity changes, the pulse width also changes.)
WINDOW COMP
detection level
(sensitivity)
The broken line shows the case
detection level has changed.
Fig. 5. Conceptual diagram of WINDOW comparator operation
AMS TC pin voltage after integration
COMP detection level
AMS OUT
AMS ON
Fig. 6. Conceptual diagram of AMS OUT operation
– 29 –
SONY [ SONY CORPORATION ]
