Smallest footprint UHF ASK/FSK receivers

Paul Boughton

Atmel Corporation has announced the availability of the new ATA5745 and ATA5746 UHF ASK/FSK receiver ICs, extending Atmel's existing portfolio of automotive RF devices.

The ATA5745 operates at 433 to 435 MHz, whereas the ATA5746 covers the 313 to 315-MHz frequency band for the standard automotive environment.

These single-chip devices are manufactured using Atmel's new RF BiCMOS process UHF6S, enabling even smaller designs.

With a size of 5 mm x 5 mm, they provide the industry's smallest footprints, a perfect fit for Remote Keyless Entry (RKE) and Tire Pressure Monitoring System (TPMS) applications.

These devices provide the best combination of large bandwidth and excellent receiving selectivity thanks to their fully-integrated filters. This allows system designers to develop a broad range of TPMS and RKE solutions, ranging from highly sophisticated to very low cost, whereas competing solutions cannot be used for such low-cost systems due to their smaller bandwidth. The new receiver ICs need few external devices and no external filters which add to the cost-efficiency of the end systems. Eight passive components, a crystal, and an RF antenna are typically all that is needed to create a receiver board application. Thanks to the ICs' large oscillation margin, designers can apply very low-cost crystals.

Due to their fast switching capability between TPMS and RKE signals, the ATA5745 and ATA5746 can be used in unified RKE/TPMS automotive application environments with different system definitions, thus eliminating the need for two separate RKE and TPMS ICs. The ICs' ability to change the modulation type between ASK and FSK, and between data rates without component changes, is important when receiving different RKE/TPMS modulation schemes and data rates. They can be operated in 1 to 20-Kbit/s Manchester FSK mode with four different baud rate ranges, selectable through the microcontroller without any hardware modification on board. The typical switching between modulation types ASK/FSK and different data rates is possible in less 1 ms.

These receiver ICs consist of an integrated IF filter, low-phase-noise VCO, PLL, and loop filter without requiring any external parts for these functional blocks. The totally integrated RF circuits achieve an image rejection of typically 30 dB. The ATA5745/ATA5746 are transparent receivers and operate in combination with a separate microcontroller for bit check and polling modes.

The active current consumption is specified at about 6.5 mA in receiving mode and is based on single-ended RF input for easy adaptation of lambda/4 or printed loop antennas.

The devices support header and blanking periods in ASK mode, as required by typical protocols used in the USA with a telegram pause length up to 52 ms.

For more information, visit