Receiver chip aims for automotive access: News from GD Technik

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Atmel's new ATA5282 is an LF ASK (amplitude shift keying) 125kHz ultra-low-power receiver IC with three input channels for three-dimensional (3D) antennas. The world's first remote control receiver IC to offer digital 8bit RSSI (receive signal strength indicator) output for improved location precision, the ATA5282 is aimed at passive entry go (PEG) systems in automotive and access control applications. By adding up to three antenna coils, a microcontroller, an RF transmitter or transceiver and a battery, a complete hands-free key fob for PEG systems can be realised.

The new ATA5282 is way ahead of competing solutions that provide analogue RSSI outputs, where the microcontroller requires an additional ADC for signal decoding.

In PEG systems the RSSI function (measurement of the magnetic field strength) is important for the precise definition of the card's location.

Comparing the detected magnetic field strength to reference values the system recognises if the card is inside or outside of the car.

If the card is not recognised to be inside the car then the engine will not start.

This prevents unintentional starting caused, for example, by children playing in the car.

The 8bit digital RSSI output, together with the three inputs for 3D measurement, increases position precision and thus system safety.

The receiver's three active input stages provide maximum wake-up sensitivity of typically better than 3mV peak-peak.

These stages measure and demodulate the input signal from the antenna coil, taking advantage of the distribution behaviour of the magnetic field strength.

The IC, therefore, serves as a sensor input for waking up the microcontroller which in turn controls the RF transmitter and sends data signals including the RSSI values.

The ATA5282 allows typical data receiving distances of up to 2.5m from the external trigger basestations, depending on the corresponding field strength.

Power consumption is a key parameter and as such is 4uA in active mode falling to 2uA in standby.

Operating voltage is 2 to 4.2V.

The ATA5282 is supplied in the extra small TSSOP8 package and has an operating temperature range of -40 to +85C.

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