CS4299 datasheet(37/52 Pages) CIRRUS

37 / 52 page

CS4299

6.1.3

Microphone Inputs

Figure 13 illustrates an input circuit suitable for dy-

namic and electret microphones. Electret, or phan-

tom-powered, microphones use the right channel

(ring) of the jack for power. The design also sup-

ports the recommended advanced frequency re-

sponse for voice recognition as specified in PC 99.

Note the microphone input to the CS4299 has an

integrated pre-amplifier. Using the 20dB bit in the

Microphone Volume Register (Index 0Eh) the

pre-amplifier gain can be set to 0 dB or 20 dB.

Figure 14 shows an external pre-amplifier circuit

for an additional 18 dB gain.

6.1.4

PC Beep Input

The PC_BEEP input is useful for mixing the output

of the “beeper” (timer chip), provided in most PCs,

with the other audio signals. When the CS4299 is

held in reset, PC_BEEP is passed directly to the

line output. This allows the system sounds or

“beeps” to be available before the AC ’97 interface

has been activated. Figure 15 illustrates a typical

input circuit for the PC_BEEP input. If PC_BEEP

is driven from a CMOS gate, the 4.7 k

Ω resistor

should be tied to analog ground instead of +5VA.

Although this input is described for a low-quality

“beeper”, it is of the same high-quality as all other

analog inputs and may be used for other purposes.

0.33

µF

220 pF

NPO

3.3

µF

6.8 K

Ω

47 k

Ω

MC33078 or

MC33178

Vrefout

MIC1

MIC2

µF

0.33

µF

X7R

2 k

Ω

47 k

Ω

0.1

µF

Ω

100 pF

NPO

Figure 13. Microphone Input

AGND

+5 VA

100

2.7

CGND

220 pF

AGND

0.068 µF

X7R

AGND

+5 VA

U1A

MC33078D

10 µF

AGND

+5 VA

6.8

10 µF

AGND

220 pF

47 k

Ω

U1B

MC33078D

1µF

X7R

MIC1/MIC2

Ω

47 k

Ω

Figure 14. Microphone Pre-amplifier

4.7 k

Ω

PC_BEEP

+5VA (Low Noise) or

AGND if CMOS Source

PC-BEEP-BUS

47 k

Ω

2.7 nF

X7R

0.1

µF

X7R

AGND

Figure 15. PC_BEEP Input

CS4299 датащи(PDF) 37 Page - Cirrus Logic

CS4299 датащи(HTML) 37 Page - Cirrus Logic

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52

датащи скачать

ссылки URL