CS4216 Datasheet, PDF (44/58 Pages) Cirrus Logic – 16-Bit Stereo Audio Codec

CDB4216
setting the MF8 pin high. Since the part is in
slave mode, the sampling rate must be set by the
ratio between CLKIN and SCLK. Assuming
that CLKIN has a frequency of 11.2896MHz,
this ratio must be eight to give a sampling rate of
22.05kHz (refer to the CS4216 data sheet). In
all slave modes, SSYNC and SCLK must be
synchronous to the master clock.
LOOPBACK MODE
The CDB4216/8 may be configured in a simple
loop back mode that only requires a power
source to operate. No controller of any type is
necessary. This mode allows a quick and simple
verification of codec operation by sampling the
LIN1 and RIN1 inputs, then looping the digital
data back to the LOUT and ROUT line outputs.
Set SPF2=SPF1=MA=1 and shunt SDOUT to
SDIN on stake header J15. This mode uses SM4
with all control settings set to zero, so no gain or
attenuation is available.
POWER SUPPLY CIRCUITRY
Figure 1 illustrates a portion of the CDB4216/8
schematic and includes the CS4216/8 along with
power supply decoupling and circuitry. The
evaluation board supports various power supply
arrangements. The factory configuration powers
the analog portion of the CS4216/8, along with
input buffers, from the VA binding post, which
needs a clean +5 Volts. The digital portions of
the CS4216/8 are factory configured to obtain
power through a 2Ω resistor from the VA supply.
The digital buffers and PLDs obtain power from
the VD binding post, which also needs +5 Volts.
Although binding posts exist for both digital and
analog grounds, only one needs to be connected
if a single supply is used for both VA and VD.
Note that the CS4216/8 is entirely on the analog
ground plane, close to the ground plane split as
required by the CS4216/8 Data Sheets. Also note
that the two ground planes are connected near
the two ground binding posts.
44
Space for a ferrite bead, L1, is provided so that
the board may be modified to power the codec
from the digital supply. Selection of L1 will de-
pend on the noise characteristics of the digital
supply used.
ANALOG INPUTS
The analog inputs consist of a pair of line level
inputs and a pair of ¹/₄" mono jacks for two mi-
crophones. BNC-to-phono adapters are included
to allow testing of the line inputs using coax or
standard audio cables.
The line-level inputs are connected to the
CS4216/8’s LIN1 and RIN1 pins. As shown in
Figure 2, the line-level inputs go through a buff-
er set to a gain of 0.5 which allows input signals
of up to 2 V_RMS. When placed in serial mode 4
with loop back, the LIN1 and RIN1 inputs are
used for analog inputs.
The microphone inputs are connected to the
CS4216/8’s LIN2 and RIN2 pins. The two mi-
crophone inputs are single-ended and are
designed to work with both condenser and dy-
namic microphones. The microphone input
buffer, shown in Figure 3, has a gain of 23 dB
thereby defining a full-scale input voltage to the
microphone jacks of 71 mV_RMS. Another 22 dB
of programmable gain is available on the
CS4216/8 to amplify smaller microphone sig-
nals.
An analog patch area with analog power and
ground, included on the CDB4216/8, provides
space to develop other input buffer circuits.
Space for headers are included, J19 and J20, to
connect to the LIN2 and RIN2 inputs. To use
these headers, the microphone traces must be
cut.
ANALOG OUTPUTS
The CS4216/8 drives the line outputs into an R-
C filter and then to a pair of BNCs labeled
DS83DB4