cxa1878q Sony Electronics, cxa1878q Datasheet - Page 26

• Manufacturer Part Number: cxa1878q
• Description: Dolby B-c Type Noise Reduction System With Recording/playback Equalizer Amplifier
• Manufacturer: Sony Electronics

REC MUTE control voltage
4. Recording level calibration
The CXA1878Q allows the recording level to be finely adjusted with a DC voltage.
Therefore, the recording level can be varied by approximately ±6dB simply by applying DC voltages of 0 to 5V
(for dual power supply) to the REC CAL pin (Pin 33).
The table below shows the input range of control voltages with the power supplies used.
3. Recording mute function
The CXA1878Q recording mute function is implemented by using a built-in recording mute circuit which varies the
recording equalizer amplifier gain according to the magnitude of the DC voltage applied to the REC MUTE pin
just like an electronic volume control. Also, any desired soft mute or fader can be freely set depending on
momentary changes in the DC voltage applied to the REC MUTE pin. Fig. 2 illustrates the recording mute
waveforms.
1
2
Pin No.
REC CAL pin voltage
Although the above range of voltages can be input to the control pin, the controllable input voltage range is
as follows.
Control voltages for this IC are referenced to the DGND pin (Pin 30).
Also note that when not using this recording level calibration function, simply leave the REC CAL pin (Pin 33)
open, so that the voltage of the REC CAL pin is matched to the internal reference voltage (2.5V), with the
recording level set for the standard gain.
42
Output level
2.5V < Vup
DGND
REC MUTE
Symbol
Vdown < 2.5V
5.0V
Less
than –90
0.0
Down (Vdown)
DGND to 2.5V
Decrease <<<< Increase
Fig. 2. Recording mute waveform
–90
0.5
Pin voltage (V)
2.5
—
– 26 –
4.5
—
2.5V
Typ.
5.0
—
2
RECOUT attenuation (dB)
NORM Tape, Norm-Speed, f = 1kHz
Remarks
1
2.5V to V
Up (Vup)
CC
CXA1878Q