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CXA2502

Dolby∗ B-C Type Noise Reduction System for Playback

Sony Semiconductor 

CXA2502M

Application Note

The CXA2502M is a stereo Dolby B-C type NR IC like the CXA1560 series.

Few external parts and smaller package can be achieved because this IC has a built-in spectral skewing circuit

and the reduced number of pins for playback.

1) Power Supply

The CXA2502M is designed to operate on either single or dual power supply.

For dual power supply, connect VCT pin to GND, and GND pin to the negative power supply.

For single power supply, connect GND pin to GND. VCC/2, generated from the internal circuit, is output to

VCT pin.

Connect a by-pass capacitor between this pin and GND.

The operating voltage range is 7.0 to 16V, which satisfies the signal handling of 12dB specified by the Dolby

Laboratories.

2) Operation Mode Control

The CXA2502M has built-in electronic switches. The operations are controlled by the DC voltages of NRSW

and MODE control pins. Table 1 shows the switching truth tables.

For single power supply, VH, VM and VL correspond to VCC, VCC/2 and GND, respectivery.

For dual power supply, VH, VM and VL correspond to VCC, GND and VEE, respectively.

Refer to "threshold" on the characteristics graph for the thresholds of the control voltages. NRSW and MODE

control pins are connected to VCT via a 50kΩ resistor, so when the pin is open, VM condition results.

NRSW

MODE

VH

C type

→

VM

B type

TAPE

VL

NR OFF

AUX

Table 1

3) Reference level

The CXA2502M Dolby level is –6dBm (388mVrms). The reference level of the playback input pin (PB IN) is

defined as the levels which provide the line output level to the line output pin (LINE OUT) in NR OFF mode.

–7–

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