CSP1027 datasheet(34/64 Pages) AGERE

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CSP1027 Voice Band Codec for

Data Sheet

Cellular Handset and Modem Applications

December 1999

Lucent Technologies Inc.

7 Application Information (continued)

Figure 29 (A—E) on page 35 illustrates five different analog output configurations. In Figure 29A, the output load is

driven in a fully differential manner. It is assumed that the load is floating, having no path to ground. Figure 29B is

similar, but ac-coupling capacitors are used. A low-pass pole is created, whose frequency should be less than

30 Hz in order to not interfere with the voice band frequency response.

In Figure 29C—E, different variations of single-ended loads are shown. In any single-ended configuration, ac-

coupling capacitors are required.

Notes:

Analog (VSSA) and digital (VSS) ground pins are tied together to prevent substrate currents from ground bounce.

Capacitors CA2, CD2, CREF, CREG1, and CREG2 should be type X7R ceramic.

Capacitors CA1 and CD1 should be tantalum or low ESR aluminum.

All capacitors should be located as close to the chip pins as possible.

Keep analog and digital grounds separate, and then join at the VSSA pin.

Keep the regulator as close to the chip as possible.

The power connections are shown when the analog and digital are run from 5.0 V. When the digital is run from a 3.3 V power supply, CD1 and

CD2 go from the 3.3 V regulator to ground, and Ra goes to the 5.0 V regulator.

Figure 28. Analog External Configurations in Preamplifier Mode (EIGS = 0)

5-7607 (F)

AOUTP

AOUTN

–

CSP1027

VDD

VSS

TO 5.0 V

REGULATOR

VSS

DIGITAL

GND

PLANE

VDDA

VSSA

REFC

Ω)

CA2

(0.1

µF)

CA1

(10

µF)

VSSA

VSS

VSSA

CREG2

(0.1

µF)

ANALOG

GND PLANE

EIGS

AUXIN

MICIN

VREG

CREG1

µF)

VSSA

Cin

(0.15

µF)

CREF

(0.22

µF)

Vin2

MICROPHONE

SHIELDING

–

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