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UAA2068

Transmit chain and synthesizer with integrated VCO for DECT

Philips Electronics 

Philips Semiconductors

Transmit chain and synthesizer with

integrated VCO for DECT

Product specification

UAA2068G

FEATURES

• Economical integrated solution for frequency generation

in DECT cordless telephones

• Integrated low phase noise 950 MHz VCO with

frequency doubler

• Local Oscillator (LO) drive (−14 dBm) for RF mixer

circuit

• Dedicated DECT PLL synthesizer

• 3-line serial interface bus

• 3 dBm output preamplifier with an integrated switch

• Low current consumption from 3 V supply

• Compatible with Philips Semiconductors ABC baseband

chip (PCD509x series).

APPLICATIONS

• 1880 to 1920 MHz DECT cordless telephones.

GENERAL DESCRIPTION

The UAA2068G BiCMOS device integrates a 950 MHz

VCO, a frequency doubler, main and reference dividers

and a phase comparator, to implement a phase-locked

loop for DECT channel frequencies. The 1.9 GHz signal is

buffered and switched, in TX mode, to drive the transmit

power amplifier (CGY20xx series) or, in RX mode, to be

used as an LO signal for the receiver mixer IC (UAA2078).

The synthesizer’s main divider is driven by the frequency

doubler output in the range from 1880 to 1920 MHz and

programmed via a 3-wire serial bus.

The reference divider ratio is fixed at 8. 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 (phase

comparator gain) is set by an external resistor at pin RSET.

The VCO is powered from an internally regulated voltage

source and includes internal varicap diodes. Its tuning

range is wider than the required band to allow for

production spreads. In a TDMA system such as DECT, the

VCO and the synthesizer are switched on one slot before

the required one to lock the VCO to the required channel

frequency. Just before the required slot, the synthesizer is

switched off, allowing open-loop modulation of the VCO

during transmission. When opening the loop, the

frequency pulling (due to switching off the synthesizer) can

be maintained within the DECT specification.

The device is designed to operate from 3 NiCd cells in

pocket phones, with low current and nominal 3.6 V

supplies. Separate power and ground pins are provided to

the different parts of the circuit. The ground leads should

be short-circuited externally to prevent large currents

flowing across the die and thus causing damage.

All supply pins (VCC) must also be at the same potential,

except VCC(CP) which can be equal to or greater than the

other supply pins (e.g. VCC = 3 V and VCC(CP) = 5 V for

wider VCO control voltage range).

ORDERING INFORMATION

TYPE NUMBER

UAA2068G

NAME

LQFP32

PACKAGE

DESCRIPTION

plastic low profile quad flat package; 32 leads; body 5 × 5 × 1.4 mm

VERSION

SOT401-1

1998 Nov 19

2

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