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CX74001
(Rev.:2000)

Rx ASIC for CDMA, AMPS, and PCS Applications

Conexant Systems 

CX74001

Rx ASIC for CDMA, AMPS, and PCS Applications

The CX74001 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 well as Advanced Mobile Phone System (AMPS) mode.

The device is a highly integrated super-heterodyne receiver. It incorporates all the

components required to implement the receiver chain, from the low-noise amplifier

(LNA) to the In-Phase and Quadrature (I/Q) demodulator stages, except for the

external Surface Acoustic Wave (SAW) filters and matching components. There

are two internal Low Noise Amplifiers (LNAs). The Cellular LNA has three-step gain

stages, and the PCS LNA gain has a bypass feature.

After RF signal amplification and filtering, the received signal is mixed down from

RF to the Intermediate Frequency (IF). There are separate mixers for AMPS,

CDMA, and PCS bands. The CDMA cellular and PCS mixers have balanced

outputs for the IF SAW filters, while the AMPS differential output can be combined

externally to mate to a single-ended SAW filter. After IF filtering, the IF signal is

amplified by a Variable Gain Amplifier (VGA) and fed to an I/Q demodulator

resulting in baseband I/Q signals at the output.

The VGA has a minimum dynamic range of 90 dB with a control voltage range from

0.5 to 2.5 Volts, and it is common to all modes. There are two VHF oscillators

which operates with external tank circuits to provide Local Oscillator (LO)

frequencies for the I/Q demodulator in the cellular and PCS bands.

Features

• Supports single, dual-band, and tri-mode handsets

• Battery cell operation (2.7 V < Vcc < 3.3 V)

• Dual Low Noise Amplifiers (800 MHz / 1900 MHz)

• PCS LNA With Bypass Feature

• Three-Step Cellular LNA Gain

• I/Q Interface

• Dual 200-600 MHz VHF Oscillators

• VCO On/Off control For Standby Current

Optimization

• CDMA Single IF Feature

• 7 x 7 mm RF Land Grid Array (RF-LGA™) package

with down-set paddle (Figure 1)

Applications

• Cellular and PCS band phones

• CDMA and AMPS modes in the cellular band:

− AMPS

− CDMA-US

− CDMA-Japan

• CDMA mode in the PCS band:

− PCS-US

− PCS-Korea

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-C. Employing BiCMOS technology, the ASIC is

designed for low cost, high performance, and a high level of integration.

A device package and pinout is shown in Figure 1, a block diagram is shown in

Figure 2, a schematic diagram is shown Figure 4, and a package drawing is shown

in Figure 5.

LNA_CTRL1 1

PCS_LNAIN 2

LNA_CTRL0 3

CELL_LNA_IN 4

VCC_RF_BIAS 5

CELL_LNA_EMIT 6

CELL/PCS 7

FM/CDMA 8

VCO_VCC 9

VCO_ON 10

CELL_TANK- 11

CELL_TANK+ 12

PCS_TANK- 13

37 VCC_MIX

36 PCS_MIXER_OUT+

35 PCS_MIXER_OUT-

34 AMPS_MIX_OUT+

33 AMPS_MIX_OUT-

32 CDMA_MIX_OUT+

31 CDMA_MIX_OUT-

30 PCS_VGA_IN+

29 PCS_VGA_IN-

28 AMPS_VGA_IN

27 CDMA_VGA_IN+

26 CDMA_VGA_IN-

25 VCC_IF

CNXT061

Figure 1. CX74001 Rx ASIC Pinout (Top View)

Data Sheet

Conexant - Preliminary.

Proprietary Information

Doc. No. 101134A

October 20, 2000

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