CXA1560S, CXA1561M/S, CXA1562M/S
Application Note
The CXA1560 series is a stereo Dolby B-C type NR IC like the CXA1330 series.
Built-in spectral skewing circuit allows smaller package.
1) Power Supply
The CXA1560 series is designed to operate on either single or dual power supply.
For dual power supply, connect VCT to GND, and VEE to the negative power supply.
For single power supply, connect VEE to GND. Vcc/2, generated from the internal circuit, is output to VCT.
Connect a by-pass capacitor between this pin and GND.
The operating voltage range is ±3.5 to ±8.0V (7.0 to 16V), which satisfies the signal handling of 12dB
specified by the Dolby Laboratories.
2) Operation Mode Control
The CXA1560 series 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, respectively.
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.
VH
VM
VL
C type
B type
NR OFF
NRSW
MODE
MPX ON
REC
(Encode)
MPX OFF
REC
(Encode)
PB
(Decode)
Table 1
3) Reference level
The CXA1560 series Dolby level is –6dBm (388mVrms), and is measured at the recording output pin (REC
OUT) in the NR OFF mode. The reference level of the recording input pin (LINE IN), playback input pin (PB
IN) and line output pin (LINE OUT) are defined as the levels which provide Dolby level at the recording
output pin in NR OFF mode.
4) MPX Filter
The CXA1560 series provides an MPX (FM multiplex) filter ON/OFF function.
Connect the MPX filter between MPX IN and MPX OUT. In MPX ON mode, the line input signal is fed to the
NR processor via the MPX buffer amplifier and MPX filter. In MPX OFF mode, the signal bypasses the
buffer amplifier and filter, and is fed directly to the NR processor. The MPX buffer amplifier gain is 10dB.
The gain from LINE IN to LINE OUT is 19dB, and from MPX IN to LINE OUT it is 13dB, for a deviation of
6dB. This means that if a filter with insertion loss of 4dB is used, there is no fluctuation between MPX ON
and MPX OFF.
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SONY [ SONY CORPORATION ]
