AD1885JST Analog Devices Inc, AD1885JST Datasheet - Page 25

• Manufacturer Part Number: AD1885JST
• Description: IC AUDIO CODEC AC'97 48-LQFP
• Manufacturer: Analog Devices Inc
• Series: SoundMAX®r
• Type: Audio Codec '97r

Specifications of AD1885JST

• Rohs Status: RoHS non-compliant
• Data Interface: Serial
• Resolution (bits): 16 b
• Number Of Adcs / Dacs: 2 / 2
• Sigma Delta: Yes
• Dynamic Range, Adcs / Dacs (db) Typ: 87 / 90
• Voltage - Supply, Analog: 4.75 V ~ 5.25 V
• Voltage - Supply, Digital: 3.15 V ~ 3.45 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-LQFP

MICROPHONE CONNECTIONS
The AD1885 contains an internal microphone preamp with 20 dB gain; in most cases a direct microphone connection as shown in
Figure 14 is adequate. If the microphone level is too low, an external preamp can be added as shown in Figure 15. In either case the
microphone bias can be derived from the Codec’s internal reference (V
the V
To meet the PC99 1.0A requirements, the MIC signal should be placed on the microphone jack tip and the bias on the ring. This
configuration supports electret microphones with three conductor plugs, as well as dynamic microphones with two conductor plugs
(ring and sleeve shorted together).
Additional filtering may be required to limit the microphone response to the audio band of interest.
LINE OUTPUT CONNECTIONS
The AD1885 Codec provides stereo LINE_OUT signals at a standard 1 V rms level. These signals must be ac-coupled before they
can be connected to an external load. After the ac-coupling, a minimal resistive load is recommend to keep the capacitors properly
biased and reduce click and pop when plugging stereo equipment into the output jack. The capacitor values should be selected to
provide a desired frequency response, taking into account the nominal impedance of the external load. To meet the PC99 specifica-
tion for PCs, testing must be performed with a 10 kΩ load, therefore a 1 µF value is recommended to achieve less than –3 dB
roll-off at 20 Hz.
REFOUT
signal can also provide the midpoint bias for the amplifier.
J1
MIC INPUT
STEREO LINE_OUT JACK
J1
J1
1
2
3
4
5
MIC INPUT
L1 600Z
L2 600Z
1
2
3
4
5
COMPONENTS
EMC
L2 600Z
L1 600Z
COMPONENTS
C1
470pF
L1 600Z
L2 600Z
EMC
COMPONENTS
C2
470pF
EMC
C2
470pF
C1
470pF
C1
470pF
AC-COUPLING
C2
470pF
MIC BIAS
AC-COUPLING
MIC BIAS
REFOUT
AC-COUPLING
PREAMP
AVDD
U1
) using a 2.2 kΩ resistor. For the preamp circuit,
AD8531
TO CODEC MIC1 OR MIC2 INPUT
FROM CODEC VREFOUT
NOTE:
IF AN OUTPUT AMP IS USED, THE
AC-COUPLING CAP VALUES WILL
DEPENDEND ON THE AMP DESIGN.
4
FROM CODEC LINE_OUT_R
FROM CODEC LINE_OUT_L
TO CODEC MIC1 OR MIC2 INPUT
FROM CODEC VREFOUT
AD1885