Electronic Design

Programmable Wireless Chip Refines ISM VHF/UHF Radios

The popular FCC-assigned industrial-scientific-medical (ISM) bands for unlicensed wireless applications are used for everything from remote keyless entry for cars to industrial telemetry applications. On top of that, many companies offer single-chip transceivers. The updated EZRadio chips from Integrated Associates will fuel that popularity.

These chips should ease implementation of ISM-band applications as well as boost performance. The IA4420 and IA4421 transceivers can be configured for any of the popular ISM frequencies, including 315, 433, 868 (Europe), and 915 MHz. Using a single external crystal, the internal phase-locked loop (acting as a synthesizer/multiplier) translates the lower-frequency crystal input to the desired higher output frequency. Modulation is frequency shift keying (FSK).

The IA4420 and IA4421 can be used with an inexpensive 8-bit microcontroller. Many of their features are fully programmable through the standard serial peripheral interface (SPI). Some of the programmable characteristics include frequency of operation, low-noise-amplifier gain, baseband bandwidth (67 to 400 kHz), data rate (up to 256 kbits/s), automatic frequency control, crystal load capacitance, output power level, and FSK deviation.

Receiver sensitivity ranges from ­105 to ­109 dBm, depending on frequency. The chips feature a received-signal-strength-indicator (RSSI) output, a data-quality detector, a received pattern recognition circuit, and a 16-bit RX data FIFO. Also, they have a power-saving sleep mode, a wake-up timer, and a low-battery detector. They operate from 2.2 to 4.5 V and consume only about 9 mA on the low-frequency bands as well.

In addition, the IA4420 and IA4421 possess an unusual built-in automatic antenna tuner. It's designed for use with a loop antenna integrated onto the pc board. The internal tuner adjusts the impedance match to ensure low standing-wave ratio and maximum power output with no needed external adjustments.

The transceivers greatly reduce the need for external components in new designs. Furthermore, their programmability and automatic antenna tuning greatly simplify and reduce production time and costs associated with final configuration and tuning.

Both chips are the same, except the IA4420 has a 4-dBm output power, while the IA4421's output is 8 dBm for longer range. Typical range measures over 100 meters outdoors and up to 40 meters indoors. Both come in a 16-pin TSSOP. Pricing starts at $2 each in large volume. A development kit with hardware and software is available.

Integration Associates

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