RF ICs MLX71120 and MLX71121 are two new members of Melexis’ highly integrated RF receiver family. Designed with dual RF inputs, the ICs are aimed at low-cost antenna diversity applications in the unlicensed Industrial-Scientific-Medical (ISM) and Short-Range-Devices (SRD) frequency bands. In addition, the chips are automotive qualified.

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Tailored for low-power and low-cost fixed frequency applications, they can address the European 863 – 870 MHz SRD bands or the ISM bands at 902 – 928 MHz in North America. Plus, the new receiver chips are applicable for the lower frequency bands at 315 MHz (e.g. in the US) or at 433 MHz (e.g. in Europe and China).

The antenna diversity scheme significantly improves the reliability of the RF communications link by selecting the RF input with the best signal quality. Another interesting feature of both receivers’ is the dual-band approach. This allows switching the RF inputs between two applications, one at 433 MHz and a second at 868 MHz.

The MLX71120 receiver features a fully integrated FSK and ASK demodulator. The IC provides the freedom to select an external IF filter, operating at one of the two common frequencies 455 kHz or 10.7 MHz. This way the receiver can be easily adapted to very narrow band or medium bandwidth applications. The sister component MLX71121 also features a fully internal demodulator, and it comes additionally with an on-chip IF filter, offering a 230-kHz bandwidth. This means no external IF filter is required for the MLX71121, according to Melexis.

The small 32-lead QFN package with a footprint of 5mm x 5mm and the fact that no bulky external ceramic filter and discriminator components are necessary to make the MLX71120/71121 the optimum choice for systems requiring the smallest PCB footprint and the lowest circuit cost, claimed the supplier.

The MLX71120/71121 operates over a wide supply voltage range from 2.1 to 5.5 V with a typical current consumption of 6.5 to 11 mA. In standby mode, the current draw is below 50 nA. The receiver input sensitivity is as low as –113 dBm for ASK and –112 dBm (MLX71120) and –107 dBm (MLX71121) for FSK signals, respectively.

Thanks to the internal IF filter and FM/FSK demodulator, the MLX71120/71121 receivers combine flexibility with high levels of circuit complexity. As a result, they dramatically reduce system costs. The receivers’ AFC feature can tolerate frequency uncertainties of the input signal.

The extended operating temperature range of -40 to +125 °C makes the parts suitable for automotive applications such as RKE, TPMS or car alarm systems. Other typical applications for the receivers include security systems, home automation, garage door openers, wireless door bells, baby monitors and wireless headsets.

The unit cost for the MLX71120/71121 is $1.5 USD in quantities of 100k.