CSP1027 Datasheet, PDF (34/64 Pages) Agere Systems – CSP1027 Voice Band Codec for Cellular Handset and Modem Applications

CSP1027 Voice Band Codec for
Cellular Handset and Modem Applications
Data Sheet
December 1999
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.
SHIELDING
CREG1
(1 µF)
MICROPHONE
CREG2
(0.1 µF)
VREG
VSSA
Cin
(0.15 µF)
MICIN
Ro _AOUTP
+
Vo
–
RL
Ro _AOUTN
–
Vo
+
CSP1027
VDD
AUXIN
+
Vin2
–
EIGS
REFC
VSS
VSSA VDDA
ANALOG
GND PLANE
CREF
(0.22 µF)
DIGITAL
GND
PLANE
VSSA
CA1
(10 µF)
VSS
Ra
(3 Ω)
CA2
(0.1 µF)
TO 5.0 V
REGULATOR
VSSA
VSS
5-7607 (F)
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)
34
Lucent Technologies Inc.