Description

The AS3977 is a low-power fully integrated ETSI, FCC and ARIB compliant FSK transmitter capable of operating at any ISM frequency in the range of 300 to 928 MHz. It is based on a sigma-delta controlled fractional-N synthesiser phase locked loop with fully integrated voltage controlled oscillator. The power amplifier output is programmable and can deliver output power ranging from –20dBm up to +10dBm. An on-chip low drop-out regulator is available in case an accurate output power independent of voltage supply variation is required.

The output signal can be shaped using a programmable Gaussian filter to minimise the occupied bandwidth and adjacent channel power. The maximum data rate can be up to 100 kb/s – depending on the required filtering.

The FSK frequency deviation is programmable up to a maximum of 64kHz.

The crystal oscillator can handle a wide range of frequencies. For narrow-band applications a temperature sensor with digital read-out is included that allows compensation of the crystal frequency drift due to temperature variation.

The AS3977 is connected to an external microcontroller via a bi-directional digital interface. The device operates at very low current consumption with a power supply range from 2.0V to 3.6V and can be powered down when not in use.

The device is fabricated in austriamicroystems advanced 0.35um SiGe-BiCMOS technology.

Key Features

• Compliant to ETSI EN 300-220, FCC CFR 47 part 15 and ARIB STD-T67
•  Multi-channel with narrow bandwidth
•  300 – 928 MHz operating frequency range (ISM)
•  Filtered FSK
•  Data rate up to 100 kb/s
•  FSK deviation programmable up to 64kHz
• Extremely low power consumption

Main Characteristics

• 2.0 – 3.6V power supply
•  Power down current consumption 100 nA (3V, 25°C)
•  Output power up to +10dBm
•  Occupied bandwidth 8.5 kHz (4.8 kb/s, FFSK, ARIB)
• Operating temperature range -40°C to +85°C

Additional Features

• Sigma-Delta controlled fractional-N synthesiser
•  Resolution of synthesiser <100Hz
•  Fully integrated PLL
•  Fully integrated voltage controlled oscillator
• 4kV ESD protection
•  Automatic antenna tuning
•  12 – 20 MHz crystal oscillator
•  On-chip temperature sensor with digital readout for AFC purposes
•  Integrated Manchester coder
•  Digital lock detector
•  Low drop-out regulator
•  Bi-directional serial interface

Applications

• Remote keyless entry systems
•  Short range radio data transmission
•  Domestic and consumer remote control units
•  Cordless alarm systems
•  Remote metering
• Low power telemetry

Block diagram for AS3977 Multi-Channel Narrowband FSK Transmitter