cxa2511aq Sony Electronics, cxa2511aq Datasheet - Page 16

• Manufacturer Part Number: cxa2511aq
• Description: Dolby B-c Type Noise Reduction System With Playback Equalizer Amplifier
• Manufacturer: Sony Electronics

4. Music sensor
The signal input from TAPEIN is added and amplified by AMP1. This signal is then input to the LPF (R4 and
C1). The LPF cut-off frequency can be adjusted by connecting the external capacitance to MSLPF pin. The
cut-off frequency is approximately 23kHz when MSLPF pin is left open.
The detection level and HPF cut-off frequency are determined with the external resistance and capacitance
connected to G1FB or G2FB at AMP2, and the signal is converted to a current.
The signal is full-wave rectified and is converted to a voltage by the internal resistance R5.
The full-wave rectified signal is smoothed. The internal resistance (R6) and external capacitance (C4)
determine the smoothing response time. The recovery time is determined by the external resistance (R10) and
capacitance (C4).
The AMP3 comparator detects whether the smoothed signal is greater or smaller than the comparator
threshold.
The comparator has approximately 2dB hysteresis.
The table below shows the example of the constant and characteristics for the external resistance and
capacitance connected to G1FB and G2FB.
FF/REW (G1)
Playback (G2)
10k
10k
R2
R1
TAPEIN1
TAPEIN2
3.9k
39k
1
1
R
VGS
Detection level
0.0047µF
0.47µF
AMP1
127k
R3
C
Fig. 6. Music sensor circuit frequency response
(dBm)
–39.5
–59.5
MSLPF
Fig. 5. Music sensor block diagram
100k
R4
Signal detection level
64p
C1
AMP2
–39.5dBm
–59.5dBm
87
G1FB
870
Vcc
– 16 –
C2
R8
G2 (NOR)
G1 (FF)
Full-wave
rectifier
G2FB
C3
R9
39.1k
R5
DGND
Frequency [Hz]
Music signal interval
detection level
Smoother
R6
1k
MSTC
–41.4dBm
–61.4dBm
R10
DGND
Vcc
11.1k
R7
C4
AMP3
DGND
Cut-off frequency
MSOUT
DVcc
870Hz
87Hz
CXA2511AQ
R11