Rainbow Electronics ATA5812 - Manual (Page 2)

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ATA5811/ATA5812 [Preliminary]
4689B–RKE–04/04
General Description
The ATA5811/ATA5812 is a highly integrated UHF ASK/FSK single-channel half-duplex
transceiver with low power consumption supplied in a small QFN48 package. The
receive part is built as a fully integrated low-IF receiver, whereas direct PLL modulation
with the fractional-N synthesizer is used for FSK transmission and switching of the
power amplifier for ASK transmission.
The device supports data rates of 1 kBaud to 20 kBaud (FSK) and 1 kBaud to 10 kBaud
(ASK) in Manchester, Bi-phase and other codes in transparent mode. The ATA5811 can
be used in the 433 MHz to 435 MHz and the 868 MHz to 870 MHz band, the ATA5812
in the 314 MHz to 316 MHz band. The very high system integration level results in few
numbers of external components needed.
Due to its blocking and selectivity performance, together with the additional 15 dB to
20 dB loss and the narrow bandwidth of a typical key fob loop antenna, a bulky blocking
SAW is not needed in the key fob or sensor application. Additionally, the building blocks
needed for a typical RKE and access control system on both sides, the base and the
mobile stations, are fully integrated.
Its digital control logic with self polling and protocol generation enables a fast challenge
response systems without using a high-performance microcontroller. Therefore, the
ATA5811/ATA5812 contains a FIFO buffer RAM and can compose and receive the
physical messages themselves. This provides more time for the microcontroller to carry
out other functions such as calculating crypto algorithms, composing the logical mes-
sages and controlling other devices. Due to that, a standard 4-/8-bit microcontroller
without special periphery and clocked with the CLK output of about 4.5 MHz is sufficient
to control the communication link. This is especially valid for passive entry and access
control systems, where within less than 100 ms several challenge response communi-
cations with arbitration of the communication partner have to be handled.
It is hence possible to design bi-directional RKE and access control systems with a fast
challenge response crypto function with the same PCB board size and with the same
current consumption as uni-directional RKE systems.
Figure 1. System Block Diagram
RF transceiver
Digital Control
Logic
Micorcontroller
Interface
Power Supply
XTO
Microcontroller
ATA5811/ATA5812
Antenna
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