CS4215 Datasheet, PDF (40/52 Pages) Cirrus Logic – 16-Bit Multimedia Audio Codec

CDB4215
GENERAL INFORMATION
The CDB4215 is designed to provide an easy
platform for evaluating the performance of the
CS4215 Multimedia Audio Codec. The board
provides a buffered serial interface for easy con-
nection to the serial port of a DSP or other serial
device. A single +5 V power supply is all that is
required to power the evaluation board.
The line input buffers are designed to accept
standard CD-level inputs of 2 V_RMS and BNC-
to-phono adapters are included to support
various test setups. The microphone inputs con-
sist of two ¹/₄" mono jacks that are designed to
accept standard single-ended dynamic or con-
denser microphones.
The line outputs are supplied via BNC jacks
with two more BNC-to-phono adapters. The
headphone output is supplied via a ¹/₄" stereo
jack and will drive headphones of 48 Ω or
greater. This includes most "walkman" style
headphones. Speaker terminals are provided and
can be connected to speakers with an impedance
of 32 Ω or greater.
The film plots of the board are included to pro-
vide an example of the optimum layout,
grounding, and decoupling arrangement for the
CS4215.
POWER SUPPLY CIRCUITRY
Figure 1 illustrates a portion of the CDB4215
schematic and includes the CS4215 codec along
with power supply circuitry. Power is supplied to
the board via two sets of binding posts, one for
digital and one for analog. The analog supply
must be +5 Volts and supplies power for the en-
tire codec (both digital and analog power supply
pins) along with the analog input buffers for the
line and microphone inputs. The digital supply is
also +5 Volts and supplies power to the digital
header buffer circuitry. Space for a ferrite bead
inductor, L1, has been provided so that the board
may be modified to power the codec from the
digital supply. Selection of L1 will depend on
the characteristics of the noise on the digital sup-
ply used.
ANALOG INPUTS
The analog inputs consist of a pair of ¹/₄" jacks
for two microphones, and a pair of BNC’s for
line level inputs. BNC-to-phono adapters are in-
cluded to allow testing of the line inputs using
coax or standard audio cables.
The line-level inputs go through a buffer, Fig-
ure 2, with a gain of 0.5 which allows input
signals of up to 2 V_RMS.
The two microphone inputs are single-ended and
are designed to work with both condenser and
dynamic mics. The microphone input buffer cir-
cuit, shown in Figure 3, has a gain of 23 dB
thereby defining a full-scale input voltage to the
mic jacks of 19.5 mVpp.
ANALOG OUTPUTS
The CDB4215 includes three analog output
paths: a pair of line output BNC’s, a stereo ¹/₄"
headphone jack, and a pair of mono speaker ter-
minals.
The CS4215 drives the line outputs into an R-C
filter and then to a pair of BNC’s. As with the
line inputs, BNC-to-phono adapters are provided
for flexibility. The line outputs can drive an im-
pedance of 10 kΩ or more, which is the typical
input impedance of most audio gear.
The stereo headphone output can drive head-
phones with an impedance of 48 Ω or greater.
This includes most "walkman" style headphones.
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DS76DB3