The AS3372E is a general purpose signal processing device
for audio tone sources. Included on-chip are:
- two channel voltage
controlled input mixer with possibility of addition external signal
dedicated 4-pole low pass voltage controlled filter with voltage
- quality final voltage controlled amplifier
- universal mixing/panning VCA-block .
With the exception of the
filter cut-off frequency, all control inputs are very low bias current,
high impedance inputs which range from 0 to + 5 volts. This feature
allows the common DAC output voltage in a microprocessor system to be
multiplexed to these inputs with only a CMOS analog multiplexer and hold
capacitors, thus eliminating the usual Sample & Hold buffers.
input VCAs of the mixer feature audio taper control scales and high
attenuation at zero control voltage. The signal inputs are low level
(80mV.P.P. for 5% THD), allowing multiple tone sources to be
conveniently mixed into each channel. “Mixer output” pin allows
additional external signals to be mixed.
A unique feature of the
24dB/octave filter is that, unlike others of this type, the passband
gain remains constant as the amount of resonance is varied, thus
eliminating the annoying drop in volume at higher resonance settings.
Other features include wide frequency control range, temperature
compensated transconductans, low noise, low control feed-through, and a
smooth behavior when swept.
The final output VCA is a current in,
current out type, allowing multiple inputs to be easily mixed into its
input, and easy interface of its output to the rest of the system. The
control scale is very linear, and the point at which the VCA shuts off
is very well defined (+100mV ± 50mV). Owing to its exceptionally low
noise and exceptionally low control feedthrough without trimming, this
VCA is well suited to being controlled by fast transient waveforms.