CS4215
FUNCTIONAL DESCRIPTION
Overview
The CS4215 has two channels of 16-bit analog-
to-digital conversion and two channels of 16-bit
digital-to-analog conversion. Both the ADCs and
the DACs are delta-sigma converters. The ADC
inputs have adjustable input gain, while the DAC
outputs have adjustable output attenuation. Spe-
cial features include a separate microphone input
with a 20 dB programmable gain block, an op-
tional 8-bit
µ-law
or A-law encoder/decoder, pins
for two crystals to set alternative sample rates,
direct headphone drive and mono speaker drive.
Control for the functions available on the
CS4215, as well as the audio data, are communi-
cated to the device over a serial interface.
Separate pins for input and output data are pro-
vided, allowing concurrent writing to and
reading from the device. Data must be con-
tinually written for proper operation. Multiple
CS4215 devices may be attached to the same
data lines.
Analog Inputs
Figure 1, the recommended connection diagram,
shows examples of the external analog circuitry
recommended around the CS4215. An internal
multiplexer selects between line level inputs and
microphone level inputs.
Input filters using a 150
Ω
resistor and a .01
µF
NPO capacitor to ground are required to isolate
the input op-amps from, and provide a charge re-
serve for, the switched-capacitor input of the
codec. The RC values may be safely changed
by a factor of two.
The HPF bit in Control Time Slot 2 provides a
high pass filter that will reduce DC offset on the
analog inputs. Using the high pass filter will
cause slight distortions at very low frequencies.
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 0.1uF capacitor. This prevents any DC
current flow.
Line Level Inputs
LINL and LINR are the line level input pins.
These pins are internally biased to the CMOUT
voltage. Figure 2 shows a dual op-amp buffer
which combines level shifting with a gain of 0.5
to attenuate the standard line level of 2 V
rms
to
56 pF
0.47 uF
Line In
Right
20 k
10 k
_
+
150
0.01 uF
NPO
LINR
(pin 16)
Example
Op-Amps
are
LT1013
5k
0.47 uF
0.47 uF
CMOUT
(pin 19)
Line In
Left
0.47 uF
20 k
+
_
10 k
150
LINL
(pin 18)
0.01 uF
NPO
56 pF
Op-amps are run
from VA1, VA2 and
AGND.
Figure 2. DC Coupled Input.
0.47 uF
Line In
Right
150
LINR
(pin 16)
0.01 uF
NPO
NPO
0.01 uF
Line In
Left
0.47 uF
150
LINL
(pin 18)
Figure 3. AC Coupled Input.
8
DS76F2
CIRRUS [ CIRRUS LOGIC ]
