UAA3545

The UAA3545 BiCMOS device is a low power, highly integrated circuit, for Digital Enhanced Cordless Telecommunication (DECT) applications.

UAA3545 features a fully integrated receiver, from antenna filter output to the demodulated data output, a fully integrated VCO, a synthesizer to implement a phase-locked loop for DECT channel frequencies and a TX preamplifier to drive the external transmit power amplifier UAA3545 (CGY20xx series or UAA359x series of Philips integrated circuits).

The synthesizer's main divider is driven by the prescaler output in the range of 1880 to 1930 MHz and is programmed via a 3-wire serial bus. The reference divider ratio is programmable to 4, 8, 12 or 16. Outputs of the main and reference dividers drive a phase comparator where a charge pump produces phase error current pulses for integration in an external loop filter (only a passive loop filter is necessary). The charge-pump current of UAA3545 is set to 4 mA for fast switching.

The VCO is powered from an internally regulated voltage source and includes integrated variable capacitance diodes and integrated coils. UAA3545's tuning range is guaranteed.The VCO and the synthesizer are switched-on one slot before the active slot to lock the VCO to the required channel frequency. Immediately before the active slot, the synthesizer is switched-off to allow open loop modulation of the VCO during transmission. When opening the loop,frequency pulling (due to switching-off the synthesizer)of UAA3545 can be maintained within the DECT specification.

The UAA3545 is designed to operate from a 3.2 V nominal supply. Separate power and ground pins are provided for the different sections of the circuit. Ground leads should be short-circuited externally to prevent large currents flowing across the die and causing damage. All VCC supplies (VCC(REG), VCC(SYN), VCC(RX) and VCC(TX)) must be at the same potential (VCC).