MAX2500B

Complete Cellular Baseband-to-RF Transmitter with PA

Highly Integrated Transmitter Is an Ideal Solution for North American CDMA Phones

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Overview

Complete Baseband-to-Duplexer System Solution
Low Transmit Current
2.7V to 3.3V Single-Supply Operation (Excluding the PA Section)
On-Chip RF PLL with Fully Monolithic VCO
78dB Gain-Control Range
3-Wire SPI/MICROWIRE Compatible
Low Rx Band Noise
Internal PA Matching
Integrated PA Protection Circuit
7mm x 7mm, 48-Lead LGA Package

The MAX2500B complete transmitter is designed for low-cost cellular applications. The miniature 7mm x 7mm transmitter includes a quadrature modulator, upconverters, drivers, power amplifiers (PAs), a monolithic voltage-controlled oscillator (VCO), and a PLL. This transmitter is tailored to operate in the cellular and US PCS frequency bands. The MAX2500B is compatible with voltage-mode baseband interfaces.

The device is based on a quasi-direct I/Q modulation scheme. The device accepts differential I/Q baseband inputs, which are upconverted to IF. The IF signal is then upconverted to the RF frequency. Each signal is then fed into separate on-chip PAs through external RF filters. PA matching is integrated onto the chip to further reduce external component count. This chip features an on-chip VCO and synthesizer to generate LO signals for both the IF and RF sections. This device integrates a novel PA protection feature to avoid PA damage in a high antenna VSWR environment.

The MAX2500B is programmed with an SPI™/MICROWIRE™-compatible 3-wire serial bus. This device features multiple modes of operation, including shutdown, idle, high power, and low power, for flexible power management. To further reduce the current consumption, the PA supply voltage can be reduced to as low as 0.5V at lower output powers. The device operates from a single 2.7V to 3.3V regulated supply and is packaged in a small 7mm x 7mm, 48-lead LGA package.

Applications