Maxim-integrated MAX2769 GPS Receiver User Manual download pdf

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Keywords: GPS, receiver, GPS receiver, MAX2769, 2769, 1575MHz, Integrated GPS Receiver, Global Positioning System

USER GUIDE 3910

User's Guide for the MAX2769 GPS Receiver

By: David Weber, Strategic Applications Engineer

Sep 22, 2006

Abstract: This note describes the MAX2769, a low-cost, single-conversion, low-IF GPS receiver chip that offers more flexibility

and performance than its predecessors. Also included is a test procedure for the MAX2769 evaluation kit (EV kit) and some

suggested SPI™ register settings for evaluation purposes.

Introduction

The MAX2769 is a low-cost, single-conversion, low-IF GPS receiver chip that offers more

flexibility and performance than its predecessors. This device covers a wide range of GPS

applications such as mobile handsets, PDAs and embedded PC, and automotive

applications. It represents the most flexible, high-performance, low-power GPS receiver

on the market.

IC Features

Low DC Power Consumption

Power required is typically 16mA to 23mA at 3V. Using SPI control, the device can be placed in idle mode, in which only the

clock buffer and temperature sensor are active and the current consumption drops to 0.5mA.

Low Associated BOM Cost and Reduced Size

The MAX2769 is a direct down-conversion design with internal filtering that eliminates the need for external filtering

components. An excellent noise figure (NF) of 1.4dB for the cascaded chain (with a 0.8dB typical first-stage NF) allows this

device to be used with a passive antenna. No external LNA is required. Because the design removes intermediate frequency

filtering and preamplification, the MAX2769 requires less board space to implement a receiver.

Flexibility for Applications Involving Active Antennas

A designer can use this device with an active antenna, as in an automotive application. For an active-antenna application, a

second internal path can be selected, which leads to a different LNA (LNA2) with lower gain (13dB vs. 19dB) and a slightly

higher NF (1.1dB vs. 0.8dB). This approach results in a power savings of 16mA to 19mA vs. 23mA to 21mA at 3V in default

mode.

A voltage is provided at pin 3 specifically to bias the active device. This voltage can be turned off through the SPI interface for

passive-antenna applications. If, however, the voltage is enabled, then LNA selection can be done automatically depending on

whether there is an active antenna present. In the LNA-gated mode, the receiver is configured to automatically switch between

the two LNAs contingent on whether a load current in excess of 1.5mA is detected at the antenna bias pin. A user does not

need separate designs for applications using active and passive antennas; the chip automatically selects the appropriate LNA

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Summary of Contents

Page 1 - IC Features

Click here for an overview of the wirelesscomponents used in a typical radiotransceiver.Maxim > Design Support > Technical Documents > User G

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for any application. If automatic LNA selection is not desired, it can be disabled through the Config1 register <14:13>.Internal Capacitive Load

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LD pin, the part can be programmed to instead provide the output signal, the reference clock, or results from a sigma-deltatest. It can also be progra

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LNA1)EV kit)IF Output GainRange (4.092MHzIF)27–18 J6 or J7–J2 55dB to 110dB3dB IF FilterPassband27–18 J7–J2 2.5MHz (default)4MHz Offset FilterRejectio

Page 6 - Digital Tests

TEST1: 1E0F401TEST2: 14C0002Make sure SHDN and IDLE are set to 1, the disabled state for both.3. Measure +3V current consumption at W19 and W20.4. Inp

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the input level to -65dBm. It should remain approximately the same (indicating AGC is working).LNA2 Tests12. Switch to LNA2 (CONF1<14:13> = 01).

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Sets AGC gain to 170 (default)Sets bit-counter length to 1024 bits (default)Selects sign/magnitude output format (default)Selects 1-bit AGC (default i

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This register:Sets fractional division ratio = 80000 (default)Selects nominal current and filter trim valuesSTRM: Test: 8000000This register:Sets nomi

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Figure 1. The MAX2769 EV kit test software screen format shows suggested settings. Related PartsMAX2769 Universal GPS Receiver Free Samples MAX4444 U

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