cxa3003r Sony Electronics, cxa3003r Datasheet - Page 30

• Manufacturer Part Number: cxa3003r
• Description: Baseband Analog Processing Ic For Dual-mode Cdma/fm Cellular Phone
• Manufacturer: Sony Electronics

10. ADC Offset Control
11. Receive Low Pass Filters
12. Transmit Signal Path Low-Pass Filters
MSB… …LSB
1111 1111
1111 1110
1000 0000
0111 1111
0000 0001
0000 0000
Input Data
The external DC voltages connected to IOFFSET and QOFFSET pins control the output of the CDMA
and FM low-pass filters to the center of the CDMA and FM ADC input range, reducing the offset to zero.
In CXA3003R, the receive low-pass filters remove residual IF frequency components and present
baseband I and Q components to the ADCs. The CDMA baseband signal extends from 1 kHz to 630
kHz. The FM baseband signal extends from 100 Hz to 14 kHz. The low-pass filters reject frequency
components above the passband while exhibiting a specific rate of attenuation in the transition band.
For FM Receive Filters two external bypass capacitors are required between pin 31 and GND,and
between pin 32 and GND as is shown in Fig.15.
Low-pass filters in the transmit signal path located after the transmit DACs attenuate much of the out-of-
band frequency components created by digital-to-analog conversion process. These filters are relatively
simple compared to the CDMA and FM low-pass filters found in the receive signal path. Since the gain of
the transmit signal path is low, the offset at the filter outputs are less critical. Transmit filter offsets are not
controlled as offsets are in the CDMA and FM receive paths.
… …
… …
Table 3 DAC Input Coding
FM Transmit DAC
Positive full-scale
99.6 % of full-scale
50.2 % of full-scale
49.8 % of full-scale
0.4 % of full-scale
Negative full-scale
Output Voltage
… …
… …
Fig. 15 FM Receive Filter
0.01µ
31
—30—
0.01µ
32
CXA3003R