XC2404 PRODUCT DETAIL

With the advent of the GPS system that uses satellites to accurately determine position on the Earth, car navigation systems that use GPS began gaining popularity in the 1990s.
GPS has recently seen a dramatic expansion of applications, including incorporation in cell phones for pedestrian navigation, and this has played an important role in producing a new generation of high-performance phones.
Digital Still Camera (DSC) with GPS has also been developed. This technology can display the location of a photograph on a map together with the latitude and longitude and the date and time. Do you ever look through your photos and wonder when and where a photo was taken? DSC with GPS will help keep your memories fresh.
The demand for miniaturized GPS applications is also rising, with incorporation in wristwatches and the development of memory-type GPS.
To support this miniaturization and higher performance of GPS, Torex Semiconductor has launched the LNA XC2404A816UR‐G. LNA stands for Low Noise Amplifier, and as the name suggests, it is an ultra-low noise amplifier that amplifies weak signals in the 1.6 GHz band of GPS.
To amplify the extremely weak signal from the satellite, the amplifier must have low noise (small NF) and the amplification must be good (high gain), and this makes the XC2404A816UR‐G an ideal IC for GPS.
In a new advance for LNAs, a CMOS process is used to achieve low energy consumption in the XC2404A816UR‐G.

Two-stage amplification enables the XC2404A816UR‐G to achieve a high gain of 26.5 dB. This value allows sufficient gain for GPS.
Torex also plans a one-stage amplifier, which will enable selection of the amplifier based on the gain required for the GPS chip set. It is a characteristic of amplifiers that when the input signal is amplified, ambient noise is also amplified, and thus the degree to which this unneeded noise can be suppressed is critical. The noise figure (NF) of the XC2404A816UR‐G is 0.94 dB, good enough for practical use. (Fig. 1, Fig. 2)

A GaAs or Si-Ge process is generally used for LNAs and an operating voltage of 3.0 V is common. By contrast, CMOS is used for the XC2404A816UR‐G, enabling the operating voltage to be reduced to 1.2 V.
CMOS is currently inexpensive and in widespread use, and thus when integrating additional functions, it now has the advantage of being a simpler process than GaAs or Si-Ge.

The small USP-8A01 package (1.5 mm x 1.5 mm x h0.6 mm) is used. In addition to the standard operating voltage of 1.2V, a self bias function requiring a single resistor enables operation at supply voltages of 1.8V, 2.85V and 3.0V.(Fig. 3)

The AC characteristics of LNAs are mainly determined by the reflection coefficient and noise figure. The characteristics are in a tradeoff relationship, and by optimizing matched constants, priority can be given to a particular characteristic. The XC2404A816UR-G is no exception, and if it is desired to further lower the noise figure (NF), this is possible by changing the circuit constants.