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CX74005

VGA + I/Q Demodulator Rx ASIC for Portable Phone Applications

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CX74005

VGA + I/Q Demodulator Rx ASIC for Portable Phone Applications

The CX74005 Application-Specific Integrated Circuit (ASIC) is a Variable Gain

Amplifier (VGA) and I/Q demodulator, intended for use in Code Division Multiple

Access (CDMA) portable phones in both cellular and Personal Communications

System (PCS) bands. As a trimode IC, it can be used in CDMA mode or Advanced

Mobile Phone System (AMPS) mode.

The device incorporates a VGA and the In-Phase and Quadrature (I/Q)

demodulator stages. The intermediate frequencies (IF) are combined through

separate buffers at the input of the VGA depending on the selected mode. The

VGA has a gain control range greater than 90 dB.

There are two Very High Frequency (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.

The noise figure, gain, and third order Input Intercept Point (IIP3) of the CX74005

are optimized to meet the system requirements for AMPS and CDMA modes as per

TIA/EIA-98-B, ANSI J-STD-018 (PCS), CDMA2000. Employing silicon bipolar

technology, the ASIC is designed for high performance, a high level of integration

and low cost.

The device package and pinout are shown in Figure 1. A block diagram of the

CX74005 is shown in Figure 2.

Features

• Supports CDMA/AMPS/PCS1900 modes

• Three battery cell operation

(2.7 V < VCC < 3.3 V).

• IF inputs and I/Q outputs

• On-chip 100 to 640 MHz oscillators

• Low power operation: <25 mA

• 32-pin Land Grid Array (LGA) 5 x 5 mm package

Applications

• Tri-mode handsets

• CDMA and AMPS modes in the cellular band:

− AMPS

− CDMA-US

− CDMA-Japan

• CDMA mode in the PCS band:

− PCS-US

− PCS-Korea

Data Sheet

GND 1

FM/CDMA 2

CELL/PCS 3

VCO_VCC 4

VCO_GND 5

CELL_TANK1- 6

CELL_TANK1+ 7

NC 8

PCS_TANK- 9

25 GND

24 VGA_AMPS

23 NC

22 VGA_PCS_IN+

21 VGA_PCS_IN-

20 VGA_CDMA_IN+

19 VGA_CDMA_IN-

18 IF_VCC

17 VGA_GC

CNXT044

Figure 1. Rx ASIC Pinout – 32-Pin LGA Package

(Top View)

Conexant - Preliminary

Proprietary Information and Specifications Are Subject to Change

Doc. No. 101252A

March 13, 2001

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