CS4216
OVERVIEW
The CS4216 contains two analog-to-digital con-
verters, two digital-to-analog converters,
adjustable input gain, and adjustable output level
control. Since the converters contain all the re-
quired filters in digital or sampled analog form,
the filters’ frequency responses track the sample
rate of the CS4216. Only a single-pole RC filter
is required on the analog inputs and outputs. The
RC filter acts as a charge reserve for the
switched-capacitor input and buffers op-amps
from a switched-capacitor load. Communication
with the CS4216 is via a serial port, with sepa-
rate pins for data into the device, and data from
the device. The filters and converters operate
over a sample rate range of 4 kHz to 50 kHz.
56 pF
Line In
Right
0.47 uF 20 k
10 k
_
+
150
0.01 uF
NPO
5k
REFBUF
RINx
(PLCC pin 25 or 26)
Example
Op-Amps
are
MC34072
or
LT1013
0.47 uF
_
0.47 uF 20 k
Line In
Left
Op-amps are run
from VA+5V and
AGND
+
10 k
150
0.01 uF
NPO
LINx
(PLCC pin 27 or 28)
56 pF
Figure 2. DC Coupled Input.
FUNCTIONAL SPECIFICATIONS
Analog Inputs and Outputs
Line In
0.47 uF
Right
RINx
(PLCC pin 25 or 26)
0.01 uF
NPO
Figure 1 illustrates the suggested connection dia-
gram to obtain full performance from the
CS4216. The line level inputs, LIN1 or LIN2
and RIN1 or RIN2, are selected by an internal
input multiplexer. This multiplexer is a source
selector and is not designed for switching be-
tween inputs at the sample rate.
Unused analog inputs that are not selected have
a very high input impedance, so they may be
tied to AGND directly. Unused analog inputs
that are selected should be tied to AGND
through a 0.1
µF
capacitor. This prevents any
DC current flow.
The analog inputs are single-ended and inter-
nally biased to the REFBUF voltage (nominally
2.2 V). The REFBUF output pin can be used to
level shift an input signal centered around
0 Volts as shown in Figure 2. The input buffers
shown have a gain of 0.5, yielding a full scale
input sensitivity of 2 V
rms
with the CS4216 pro-
DS83F2
150
NPO
0.01 uF
Line In
Left
0.47 uF
150
LINx
(PLCC pin 27 or 28)
Figure 3. AC Coupled Input
grammable gain set to 0. If the source imped-
ance is very low, then the inputs can be AC
coupled with a series 0.47
µF
capacitor, elimi-
nating the need for external op-amps (see Figure
3). However, the use of AC coupling capacitors
will increase DC offset at 0dB gain (see Analog
Characteristics Table).
The analog outputs are also single-ended and
centered around the REFBUF pin. AC coupling
capacitors of >1
µF
are recommended.
9
CIRRUS [ CIRRUS LOGIC ]
