參數(shù)資料
型號(hào): CPS1027-J
英文描述: Telecommunication IC
中文描述: 通信集成電路
文件頁(yè)數(shù): 7/64頁(yè)
文件大?。?/td> 870K
代理商: CPS1027-J
Agere Systems Inc.
7
Data Sheet
January 2002
CSP1027 Voice Band Codec for
Cellular Handset and Modem Applications
4 Architectural Information
(continued)
Following the low-pass filtering and decimation to 8 kHz, the 16-bit two's complement PCM can go directly to the
output register,
cdx(A/D)
, or go to a third-order IIR digital high-pass filter and then to the output register. The –3 dB
corner frequency of the high-pass filter is approximately 270 Hz. This filter exceeds the VSELP preprocessing
requirements of IS-54 for attenuation of 60 Hz and 120 Hz signals. The high-pass filter is selected by writing the
HPFE field in the
cioc3
register (see Table 10 on page 29). The default value upon reset is the high-pass filter
enabled (HPFE = 0).
Figure 4. CSP1027 A/D Path When in the Preamplifier Mode (EIGS = 0)
Figure 5. CSP1027 A/D Path in the External Gain Select Mode (EIGS = 1)
4.2.5 A/D Path Frequency Response
The composite digital filters (decimator, LPF, and HPF)
meet the ITU-T G.712 voice band frequency response
specifications and are suitable for IS-54, JDC, and
GSM digital cellular applications. Figures 6 through 9
show the A/D and D/A frequency response without the
optional high-pass filter (HPF). Figures 10 and 11 show
the group delay characteristics of the A/D and D/A with-
out the high-pass filter. Figures 12 and 13 show the fre-
quency response of the high-pass filter. Figures 14 and
15 show the group delay characteristics of the high-
pass filter. In all figures, the frequency is normalized to
the sampling frequency f
S
(i.e., frequency/f
S
). To get the
actual frequency, multiply the normalized frequency by
f
S
. The absolute delay and delay distortion have been
normalized to the sampling period 1/f
S
(i.e., delay x f
S
).
To obtain the actual delay, divide the normalized delay
by f
S
. The templates shown in Figures 7 through 9,
11 through 13, and 15 correspond to the limits in the
ITU-T G.712 specification where f
S
= 8.0 kHz.
4.2.6 PCM Saturation Versus Analog Input Levels
16-bit two's complement saturation is employed to pre-
vent wraparound during input overload conditions. The
saturation is hard-limiting:
0x7fff = maximum positive level
0x8000 = minimum negative level
The analog levels that correspond to the saturation lev-
els for the three input modes are outlined in Table 14 on
page 51.
MICIN
PREAMPLIFIER
AND AA-FILTER
A/D
AND
FILTERS
+
Rin
Cin
Vin1
AUXIN
Rin
Cin
Vin2
EXTERNAL
COMPONENTS
5-7592 (F)
MICIN
A/D
AND
FILTERS
+
Rfb
Cfb
AUXIN
EXTERNAL
COMPONENTS
INTERNAL
SIGNAL GND
INTERNAL
SIGNAL GND
Rin
Cin
+
5-7593 (F)
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