CXA1946BQ/BR
Description of Operation
The CXA1946BQ/BR is a serial control electronic volume IC designed for use in audio systems.
The internal circuit of the IC consists of the following blocks:
1. Input selector
2. Volume
3. Loudness
4. Tone control
5. Fader
6. VCT buffer
7. Serial data I/O
8. Zero-cross detector (with timer)
9. Power-off mute
The operation of each block and notes on their use are described below.
Note that when the circuits for channels 1 and 2 are identical, the suffix “X” is added to pin names and device
names in order to distinguish between the two channels.
1. Input selector
There are two channels (stereo), each with four systems of input pins; the input selector selects one of
those input systems.
The gain between the input pins and the output pin of the input selector can be set independently for each
input system, except the gain for inputs 3 and 4 is common.
Determine the gain for each system through the settings of the feedback circuit constants as shown in Figs.
1 and 2. When each input gain is set to × 1, short INAOX and GAIN × 1,GAIN × 2,GAIN × 34.
The input impedance is 50kΩ (typ.) for each input.
The output impedance for INAO1 and INAO2 is low impedance (roughly 0Ω). The gain is not affected by the
load impedance.
VCT
GAINX2
GAINX1
GAINX34
INAOX
INX4
50k
50k
50k
50k
INX3
INX2
INX1
Fig. 1. Input Selector (1)
– 17 –
SONY [ SONY CORPORATION ]
