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PACAC97

PC Audio Resistor Network

California Micro Devices => Onsemi 

CALIFORNIA MICRO DEVICES

PACAC97

PC Audio Resistor Network

Features

Applications

• Signal conditioning and gain setting resistors for

all standard audio functions

• Low noise thin film resistors ±1% match

• Better than 1% matching between channels

• Gain modification by changing resistors

externally

• Better than –90dB inter-channel and channel-to-

channel crosstalk

• Single 28-pin QSOP package

• Saves board space and reduces assembly cost

• Analog audio system for Pentium II Class personal

computers, used in conjunction with Audio Codec,

CS4297 or AD1819A.

Product Description

High quality audio systems have become standard for

most personal computers. Furthermore, the audio

functions have been migrating to the motherboard,

putting pressure on available board space. The

PACAC97 provides the components necessary for signal

conditioning of analog audio inputs for an AC97 compli-

ant Codec as well as gain setting resistors for head-

phone and microphone amplifiers. Since analog signal

levels can be as high as 2Vrms, the PACAC97 provides

6dB of attenuation (to 1Vrms) for LINE-IN, AUX, and CD

inputs. The CD line level inputs of the PACAC97 have an

additional ground signal, CD_GND, that supports the

pseudo differential amplifier present in AC97 Codecs.

This feature facilitates attenuation of common mode

ground noise typically present at the output of CD ROM

drives. Connecting the CD pins as indicated in the

application circuit provides attenuation of common mode

noise from the CD inputs, thereby producing a higher

quality CD signal. Finally, the device provides gain-

setting resistors for the headphone and microphone

amplifiers. The PACAC97 provides exceptional inter-

channel and channel-to-channel crosstalk attenuation

necessary for high quality audio.

The PACAC97 provides performance, high reliability, and

low cost through manufacturing efficiency, utilizing high

volume and low cost IC manufacturing and processes.

The process yields low noise and highly stable resistors

demanded in audio applications. In addition, the 28-pin

QSOP package is an industry standard that is easy to

handle in manufacturing and provides package reliability

SCHEMATIC CONFIGURATION

AMP1–

AMP_OUT2

AMP_OUT1

IN1

AMP2– IN2

28

27

26

25

24

23

R23

33KΩ

R23

22KΩ

R22

33KΩ

R21

22KΩ

GND

22

MIC IN MIC+

MIC_AMP_OUT

MIC–

CD_R

CD_GND

CD_L

21

20

R20

R19

4.7KΩ 33KΩ

19

18

R17

100KΩ

17

16

15

R13

6.8KΩ

R11

3.4KΩ

R9

6.8KΩ

R18

4.7KΩ

R15

510KΩ

R14

6.8 KΩ

R12

3.4KΩ

R10

6.8KΩ

R16

100KΩ

R2

6.8KΩ

R4

6.8KΩ

R5

6.8KΩ

R7

6.8KΩ

R1

6.8KΩ

R3

6.8KΩ

R6

6.8KΩ

R8

6.8KΩ

1

2

3

4

5

6

7

8

9

10

11

12

13

LINE_IN_L

AC97LINE_R

GND

GND

AC97CD_GND

AC97AUX_R

AUXIN_L

LINE_IN_R

AC97LINE_L

AC97MIC

AC97CD_R

AC97CD_L

AC97AUX_L

14

AUXIN_R

© 2000 California Micro Devices Corp. All rights reserved.

9/27/2000 215 Topaz Street, Milpitas, California 95035

Tel: (408) 263-3214

Fax: (408) 263-7846

C0441098

www.calmicro.com

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