U3550BM

· All PLLs and most of the oscillators are integrated
· All functions and channel selection controllable by serial bus
· Receiver Mixer 1 with integrated image rejection
· Up to 25 channels selectable depending on CT0 standard
· Integrated oscillator circuit with external crystal (11.15 MHz)
· Programmable carrier-modulation frequency

· CT0 (USA, France, Spain, Netherlands, Portugal, Korea, Taiwan, New Zealand, China)
· Narrowband voice and data transmitting / receiving systems

The U3550BM is a radio-frequency IC for analogcordless telephone applications in the 26/50-MHz band (CTO standard). The IC performs full duplex communication. The transmitting and receiving frequency depends on whether the IC is used in the handset or in the base station.

The U3550BM's frequency converter consists of an FM transmitter with switchable output power and receiver Mixer 1 in the same unit. A two-wire bus interface U3550BM can be used for frequency control as well as for switching the transmitter's power amplifier and the receiver. Finefrequency adjustment of the reference crystal oscillator isprogrammable.

The receive part of U3550BM is designed for a double-conversion architecture. The incoming radio-frequency signal will be filtered and amplified before reaching the first mixer. At this stage, the RF signal of U3550BM will be converted down to the first intermediate frequency (10.7 MHz) by using a local adjustable oscillator (VCO3). The frequency of this oscillator is controlled by the PLL.

The transmitter part of U3550BM contains two PLL-controlled VCOs. The frequency modulation is accomplished bysuperposing the incoming audio signal on the first PLLcontrol voltage. In this system, the frequency is a productof mixing VCO1 with local oscillator (VCO3). The FMmodulated carrier of U3550BM is amplified by external power amplifier before entering the output filter and the antenna connector.