MICRF620 Datasheet | Micrel Semiconductor

Description The MICRF620 is a self-contained frequency shift keying (FSK) transceiver module, intended for use in half-duplex, bidirectional RF links. The multi-channeled FSK transceiver module is intended for UHF radio equipment in pliance with the European Telemunication Standard Institute (ETSI) specification, EN300 220. The transmitter consists of a fully programmable PLL frequency synthesizer and power amplifier. The frequency synthesizer consists of a voltage-controlled oscillator (VCO), a crystal oscillator, dual modulus prescaler, programmable frequency dividers, and a phase-detector. The output power of the power amplifier can be programmed to seven levels. A lock-detect circuit detects when the PLL is in lock. In receive mode, the PLL synthesizer generates the local oscillator (LO) signal. The N, M, and A values that give the LO frequency are stored in the N0, M0, and A0 registers. The receiver is a zero intermediate frequency (IF) type that makes channel filtering possible with low-power, integrated low-pass filters. The receiver consists of a low noise amplifier (LNA) that drives a quadrature mix pair. The mixer outputs feed two identical signal channels in phase quadrature. Each channel includes a pre-amplifier, a third order Sallen-Key RC low-pass filter that protects the following switched-capacitor filter from strong adjacent channel signals, and a limiter. The main channel filter is a switched-capacitor implementation of a six-pole elliptic low pass filter. The cut-off frequency of the Sallen-Key RC filter can be programmed to four different frequencies: 100k Hz, 150k Hz, 230k Hz, and 350k Hz. The I and Q channel outputs are demodulated and produce a digital data output. The demodulator detects the relative phase of the I and the Q channel signal. If the I channel signal lags behind the Q channel, the FSK tone frequency is above the LO frequency (data “1”). If the I channel leads the Q channel, then the FSK tone is below the LO frequency (data “0”)....