General Description
The TH7108 FSK/ASK/FM transmitter IC is designed for applications in the European 868MHz industrial-scientific-medical (ISM) band, according to the EN 300 220 telecommunications standard. It can also be used for any other system with carrier frequencies ranging from 850 MHz to 920 MHz (e.g. for applications in the US 915MHz ISM band).
The transmitters carrier frequency fc is determined by the frequency of the reference crystal fref that is used. The integrated PLL synthesizer ensures that each RF value, ranging from 850 MHz to 920 MHz, can be achieved by using a crystal with reference frequency according to: fref = fc/N, where N = 32 is the PLL feedback divider ratio.

FEATUREs
❐ Fully integrated, PLL-stabilized VCO
❐ Frequency range from 850 MHz to 920 MHz
❐ FSK through crystal pulling allows modulation from DC to 40 kbit/s
❐ High FSK deviation possible for wideband data transmission
❐ ASK achieved by on/off keying of internal power amplifier
❐ FM possible with external varactor
❐ Wide power supply range from 2.2 V to 5.5 V
❐ High over-all frequency accuracy
❐ Very low standby current
❐ Adjustable output power range from -15 dBm to +1 dBm
❐ Adjustable current consumption from 6.2 mA to 12.5 mA
❐ FSK deviation and center frequency independently adjustable
❐ Differential output well-suited for loop antenna
❐ External clock available for µC drive, down to 1.9 V supply
❐ ”Clock only” mode
❐ Conforms to EN 300 220 and similar standards

APPLICATION Examples
❐ Keyless car and central locking
❐ Low-power telemetry
❐ Alarm and security systems
❐ General digital data transmission
❐ General analog audio signal transmission