RF250-32 Ver la hoja de datos (PDF) - Conexant Systems
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RF250-32 Datasheet PDF : 17 Pages
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RF250
Rx ASIC for CDMA, AMPS, and PCS Applications
The RF250 Application-Specific Integrated Circuit (ASIC) is a
triple-mode, dual-band receiver (Rx) intended for use in Code
Division Multiple Access (CDMA) portable phones in both
cellular and Personal Communications System (PCS) bands. As
a dual mode IC, it can be used in CDMA mode or Advanced
Mobile Phone System (AMPS) mode.
The device incorporates all the components required to
implement the receiver front end and the In-Phase and
Quadrature (I/Q) demodulator stages except for the filter blocks
and PCS Low Noise Amplifier (LNA). Besides a cellular band
LNA, there are separate mixers for AMPS, CDMA 800 MHz, and
PCS bands. The AMPS mixer output is single-ended, followed
by the AMPS Intermediate Frequency (IF) Surface Acoustic
Wave (SAW) filter. The cellular and PCS mixers have balanced
outputs for the CDMA IF SAW filters. The mixers are followed by
an IF Variable Gain Amplifier (VGA) and an I/Q demodulator.
The outputs from the filters are combined through separate
buffers at the input of the VGA. The buffers are enabled
depending on the selected mode. The VGA has a gain control
range greater than 90 dB. There are two VHF oscillators that
operate with external tank circuits. They provide signals to the
Local Oscillator (LO) for the I/Q demodulator in the cellular and
PCS bands.
Features
• Supports CDMA/AMPS/PCS1900
modes.
• Three battery cell operation
(2.7 V < VCC < 3.6 V).
• Higher level of integration.
• I/Q outputs.
• On-chip 100 to 640 MHz oscillators.
• Low power operation: <60 mA.
• 48-pin Thin Quad Flat Pack (TQFP)
package with downset paddle.
Applications
• Tri-mode handsets.
• CDMA and AMPS modes in the
cellular band:
- AMPS
- CDMA-US
- CDMA-J
• CDMA mode in the PCS band:
- US-PCS
- K-PCS
The noise figure, gain, and third order Input Intercept
Point (IIP3) of each stage in the receiver chip are
optimized to meet the system requirements for AMPS
and CDMA modes as per TIA/EIA-98-B and ANSI J-
STD-018 (PCS). Employing silicon bipolar technology,
the ASIC is designed for high performance and a high
level of integration.
GND
The device package and pinout are shown in Figure 1. A CELL_LNA_DECOUPLE
NC
block diagram of the RF250 is shown in Figure 2.
CELL_LNA_IN
VCC1
CELL_BIAS_SET
CELL/PCS
FM/CDMA
VCC2
GND
CELL_TANK-
CELL_TANK+
48 47 46 45 44 43 42 41 40 39 38 37
1
36
2
35
3
34
4
33
5
32
6
31
7
30
8
29
9
28
10
27
11
26
12
25
13 14 15 16 17 18 19 20 21 22 23 24
PCS_IF_OUT+
PCS_IF_OUT-
AMPS_IF_OUT
CDMA_IF_OUT+
CDMA_IF_OUT-
CELL_MIX_BYPASS
VGA_PCS_IN+
VGA_PCS_IN-
VGA_AMPS_IN
VGA_CDMA_IN+
VGA_CDMA_IN-
VCC3
Data Sheet
C452
Figure 1. RF250 Rx ASIC Pinout – 48-Pin TQFP
Package With Downset Paddle
Conexant Systems, Inc.
Doc. No. 101251A
August 24, 2000
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