cs4215 Cirrus Logic, Inc., cs4215 Datasheet - Page 9

• Manufacturer Part Number: cs4215
• Description: 16-bit Multimedia Audio Codec
• Manufacturer: Cirrus Logic, Inc.

1 V
level shift the signal. This level shifting allows
the line inputs to be DC coupled into the
CS4215. Minimum ADC offset results when the
line inputs are DC coupled (see Analog Charac-
teristics Table).
Figure 3 shows an AC coupled input circuit for
signals centered around 0 Volts. The anti-alias-
ing RC filter presents a low impedance at high
frequencies and should be driven by a low im-
pedance source.
Microphone Level Inputs
Internal amplifiers with a programmable 20 dB
gain block are provided for the microphone level
inputs, MINR and MINL. Figure 4 shows a sin-
gle-ended input microphone pre-amplifier stage
with a gain of 23 dB. AC coupling is mandatory
for these inputs since any DC offset on the input
will be amplified by the codec.
DS76F2
rms
. The CMOUT reference level is used to
MINR
MINL
(Mono)
10 uF
10 uF
+
+
Figure 4. Optional Microphone Input Buffer
2.2 k
2.2 k
C6
R3
C3
R6
1 uF
1 uF
C5
C2
+
+
VA+
2
3
R5
50 k
R2
50 k
5
6
22.1 k
C1
R4
8
4
22.1 k
A =20 dB
MC33078 or
MC33178
R1
7
1
560 pF
NPO
U2
C4
560 pF
NPO
0.1 uF
C7
C8
The 20 dB gain block may be disabled using the
MLB bit in Control Time Slot 1. When dis-
abled, the inputs become line level with full
scale inputs of 1 Vrms.
Adjustable Input Gain
The signals from the microphone or the line in-
puts are routed to a programmable gain circuit
which provides up to 22.5 dB of gain in 1.5 dB
steps. Level changes only take effect on zero
crossings to minimize audible artifacts, often re-
ferred to as "zipper noise". The requested level
change is forced if no zero crossing is found af-
ter 511 frames (10.6 ms at a 48 kHz frame rate).
A separate zero crossing detector exists for each
channel.
Analog Outputs
The analog outputs of the DACs are routed via
an attenuator to a pair of line outputs, a pair of
+
0.47 uF
0.47 uF
1 uF
C48
C45
C47
R56
150
C46
150
R57
0.01 uF
NPO
0.01 uF
NPO
CMOUT
Microphone
Microphone
Input Right
Input Left
(pin 17)
(pin 15)
CS4215
9