CX74037

Transmit RF IC for TDMA or AMPS Applications

Data Sheet

Conexant Proprietary

Doc. No. 101103A

Data Subject to Change

September 27, 2000

PCS-TDMA

RF Out

Cell RF Out

PCS RF SAW

TX RFIC

CX74037

Cell LO

Cell RF SAW

PCS LO

LPF or BPF

÷ 2

IF LO IN

Vvga

101103A-2_080900

2

2

VCC

I Data

Q Data

VGA En

PA Driver En

PULL En

Band Select

IF Select

Figure 2. CX74037 Functional Block Diagram

Technical Description

The CX74037 is a TDMA transmitter for the 800 MHz and 1900

MHz bands. It also can be used as an FM transmitter in AMPS

mode at the 800 MHz band. A band select command chooses

between the 800 MHz band and the 1900 MHz band. A mode

select command chooses between TDMA and AMPS mode.

The chip consist of an I/Q modulator, IF LO input buffer, IF VGA,

two upconverters for the 800 MHz and 1900 MHz bands, and

two PA drivers for the 800 MHz and the 1900 MHz bands.

I/Q Modulator. The I/Q modulator converts the incoming I/Q

signal to an IF signal using one of the two local oscillator inputs.

This signal is fed directly to the VGA amplifier.

Variable Gain Amplifier. The VGA is a differential amplifier that

receives its signal from the I/Q modulator, amplifies it, and then

is taken off-chip to be filtered before routing it to the

upconverter. A dynamic range of 90 dB is available on the

amplifier. A DC voltage of 0.2 to 2.5 V is needed to control the

gain of the amplifier.

Upconverters. The 800 MHz and 1900 MHz upconverters

receive the IF signal from the VGA amplifier. Each upconverter

requires an external LO controlled by an external Phase Locked

Loop (PLL). The band select command switches between the

800 MHz and the 1900 MHz bands.

PA Drivers. Two PA drivers are included, the 800 MHz driver

and the 1900 MHz driver. Each driver takes its input from the

upconverter after passing through an image rejection filter. The

driver amplifies the signal and sends it to an external PA.

Electrical and Mechanical Specifications ________________

The signal pin assignments and functional pin descriptions are

found in Table 1. The absolute maximum ratings of the

CX74037 are provided in Table 2, the recommended operating

conditions are specified in Table 3. Electrical characteristics for

the CX74037 are shown in Table 4. Table 5 defines the control

signal logic.

Figure 3 provides the package dimensions for the 48-pin, 7x7

LGA package.

ESD Sensitivity

The CX74037 is a static-sensitive electronic device. Do not

operate or store near strong electrostatic fields. Take proper

ESD precautions.