Microchip Rolls Out Single-Chip Solution for Passive Keyless Entry

Engineers designing radio frequency systems for passive keyless entry and tire pressure monitoring may now be able to swap two chips for one, thanks to a new device that combines a microcontroller with a three-channel analog transponder.

Known as the Microchip PIC16F639, the new chip enables designers of RF devices, such as automotive passive keyless entry systems, to more easily package electronic components in handheld keyfobs. Microchip Technology, Inc., makers of the new device, say that it can also be used in tire pressure monitoring, computer access, door locks, gate openers, and even “smart” doggie doors.“When you put a chip inside somebody’s keyfob, size is a big factor,” notes Fanie Duvenhage, a product marketing manager for Microchip Technology, Inc. “The board-space savings alone can be very important.”Duvenhage adds that many keyfob designers are challenged when they try to incorporate antenna-based transmitters, coils, and batteries, along with microcontrollers, inside a device that fits in the palm of a hand. The new device makes the design process easier by replacing the conventional 14-pin and 20-pin packages with a single 20-pin SSOP (small shrink outline package), thus freeing up room inside the keyfob.In its 20-pin package, the PIC16F639 incorporates an 8-MHz internal oscillator, 3.5 Kbytes of flash memory, 128 byes of RAM, 256 bytes of EEPROM, 8-bit and 16-bit timers, and three channels for 125-KHz wireless communications. The device also includes Microchip’s integrated “Keeloq” peripheral (a passive keyless entry feature) and nanoWatt power consumption. In 10,000-unit quantities, it costs $2.18 each.Microchip engineers see the chip as an alternative to passive keyless entry systems based on application-specific integrated circuits (ASICs). By employing a microcontroller instead of an ASIC, they say, they’ve added feature possibilities.“ASICs don’t drive your costs up, but they do reduce your flexibility,” Duvenhage says. “Having a microcontroller in there gives you a lot more flexibility when you want to implement new features.”The company says that the PIC16F639 is also drawing interest in applications outside passive keyless entry. In automotive, its flexibility makes it a candidate for tire pressure monitoring systems, which need an RF transponder for communication between the dashboard and tires. Outside of automotive, it’s seeing use in RFID, hospital access, garage door openers, remote sensing and home security. Microchip engineers say that the product has also drawn interest from makers of smart doggie doors, who want to use it as part of a smart system that would recognize house pets and prevent unwanted animals from entering homes.“We’re seeing an enormous number of different applications,” Duvenhage says. “Passive keyless entry has enabled us to bring the costs down and to open up a lot of new possibilities.”