Maxim Integrated MAX2769 GPS Receiver User Manual
User's guide for the max2769 gps receiver, Introduction, Ic features
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APP 3910
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
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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