Adding wireless capability to applications that require short-range, low-data-rate operations and low cost has never been easier, thanks to industrial-scientific-medical (ISM) bands. Many companies in the ISM-band market have introduced a number of chips and modules recently.
MAXIM INTEGRATED PRODUCTS
The MAX7060 (Fig. 1), a frequency- and power-agile ASK/FSK transmitter, enables the use of a single design for multiple applications. Thanks to its fractional-N synthesizer, programming is possible over a 280- to 450-MHz frequency range with a single crystal reference. The RF output power is SPI-programmable (serial peripheral interface) between +14 and –14 dBm in 1-dBm steps, maximizing transmit power while complying with multiple regulatory requirements.
To maintain a good output-power match across a broad range of frequencies, the MAX7060 contains a programmable matching capacitor that’s connected in parallel with the power amplifier (PA) output. Such integration and flexibility suits the transmitter for power-sensitive applications like home-security systems, remote controls, and garage-door openers.
The transmitter operates from a single 2.1- to 3.6-V power supply, or internal regulators can be used for supply voltages between 4.5 and 5.5 V. It draws about 5 nA in shutdown mode. The device is fully specified from –40°C to 125°C, and it comes in a 4- by 4-mm, 24-pin TQFN (thin quad flatpack, no leads) package. Prices start at $2.60 lots of 1000 and greater.
For complete ready-to-go modules, there’s the CXT/CXR module family (Fig. 2) from Radiometrix. This transmitter/receiver pair provides a complete remote-control switch function. The combo delivers reliable, long-range operation in situations where existing wideband solutions can’t offer adequate range or where band congestion requires multi-channel operation.
The CXT and CXR modules target tasks that just call for a simple on/off control function (such as flood-light control, machine override shutdown, etc.) without the need for any additional external circuitry such as a microprocessor or dedicated encoder/decoder IC. This minimizes the size, bill-of-materials cost, and software overhead associated with system designs that employ these modules.
The pair supports data rates of up to 5 kbits/s and provides 32 frequency-channel operation (12.5- or 25-kHz channels) in any of the 173.200- to 173.325-MHz (UK), 150.825- to 152.450-MHz (Australia), 433.875- to 434.650-MHz (EU), or 458.525- to 459.1-MHz (UK) frequency bands (plus other custom VHF bands on request). Thus, the modules can meet the RF requirements of many different geographical regions.
The CXR receiver offers a better than –118-dBm usable sensitivity, while drawing only 20 mA from a 3.1- to 15-V rail. The matching CXT transmitter comes in 10 mW (35 mA from 3.1 to 15 V) or 100 mW (95 mA from 4.1 to 15 V) versions, depending on specific band regulations.
The integrated control coder/decoder employs a highly noise-tolerant, bi-phase coded data stream, including generous preamble/framing sequences, cyclic redundancy code (CRC) error detection to minimize false activations, and a 16-bit user programmable address. Users can easily program all operating parameters (channel, address, frequency table setup) via a simple serial interface. Put together, these features give the user a reliable remote actuator with an operating range of up to 1 km. Key applications include lighting control, security/fire/lone-worker alarms, “machine stop” systems, and generic industrial quality on/off switching mechanisms.
The CXT and CXR come in compact shielded housings, measuring 33 by 23 by 9 mm and 46 by 23 by 9 mm, respectively, with pins for printed-circuit-board mounting. The modules have an operating temperature range of –20°C to 55°C and conform fully with EN 300 220-3 and EN 301 489-3 standards. Class 1 (to EN300-220-v2.3.1) receiver versions are also available.
RF Micro Devices’ ML2730 (Fig. 3) is a single-chip, fully integrated, frequency-shift-keyed (FSK) transceiver with integrated PA and low-noise amplifier (LNA). It’s optimized for a variety of wireless media applications (audio, video, and data) operating in the 2.400- to 2.485-GHz unlicensed ISM band.
The high-data-rate capability of the ML2730 supports streaming applications like wireless audio and wireless video. It’s mode-selectable for operation with digital cordless phones (DSSS or DECT). Moreover, the device suits a wide range of radio-controlled applications. Because the PA and LNA are integrated on one chip, robust wireless links with improved sensitivity and output power are possible, and it reduces both cost and board size.
The ML2730 contains a dual-conversion, low-IF receiver with all channel selectivity on-chip. Also, on-chip IF filtering, IF gain, and demodulation eliminates the need for any external IF filters or production tuning. Integration of a post-detection filter and a data slicer completes the receiver.
An adjustment-free closed-loop modulator modulates the on-chip voltage controlled oscillator (VCO) filtered data. An upconversion mixer, buffer/predriver, and PA produce a typical output power of +21 dBm. A fully integrated fractional synthesizer is used in both receive and transmit modes.
Power-supply regulation is included, providing circuit isolation and consistent performance over supply voltages between 2.8 and 3.6 V. The chips are available now.