Low voltage high performance mixer FM IF system

The SA608 is a low voltage high performance monolithic FM IF system incorporating a mixer/oscillator, two limiting intermediate frequency amplifiers, quadrature detector, logarithmic received signal strength indicator (RSSI), voltage regulator and audio and RSSI op amps. The SA608 is available in 20-lead dual-in-line plastic, 20-lead SOL (surface-mounted miniature package) and 20-lead SSOP package.

The SA608 was designed for portable communication applications and will function down to 2.7V. The RF section is similar to the famous NE605. The audio output is buffered. The RSSI output has an internal amplifier with the feedback pin accessible. The SA608 also has an extra limiter output. This signal is buffered from the output of the limiter and can be used to perform frequency check. This is accomplished by comparing a reference frequency with the frequency check signal using a comparator to a varactor or PLL at the oscillator inputs.