T2803 View Datasheet(PDF) - Atmel Corporation
Part Name
Description
MFG CO.
'T2803' PDF : 28 Pages View PDF
T2803
3. Functional Description
3.1 Receiver
The RF signal at RF_IN is fed to an image rejection mixer IR_MIXER with its differential outputs
MIXER_OUT1 and MIXER_OUT2 driving an IF-SAW filter at 110.592 MHz or 112.32 MHz. The
IF_AMP1 and IF_AMP2 IF amplifiers with an external IF_TANK and an integrated RSSI function
feed the signal to the demodulator DEMOD working at f = fIF/2 (≈ 55 MHz) and finally to an inte-
grated baseband filter BB. For demodulator tunning in production an integrated 5-bit
digital-to-analog (D/A) converter is provided to control the on-chip varicap diode.
3.2 Transmitter
The transmit data at TX_DATA is filtered by an integrated Gaussian Filter GF and fed to the fully
integrated VCO operating at twice the output frequency. After modulation the signal is fre-
quency-divided by 2 and fed via a TX/RX SWITCH to the TX_DRIVER. This bus-controlled
driver amplifier supplies typically +3 dBm output power at TX_OUT. A ramp-signal generator
RAMP_GEN, providing a ramp signal at RAMP_OUT for the external power amplifier, is inte-
grated. The slope of the ramp signal is controlled by a capacitor at the RAMP_SET pin.
3.3 Synthesizer
The IR_MIXER, the TX_DRIVER and the programmable counter PC are driven by the fully inte-
grated VCO (including on-chip inductors and varactors). The output signal is frequency-divided
to supply the desired frequency to the TX_DRIVER, 0/90 degree phase shifter for the IR_MIXER
and to be used by the PC for the phase detector PD (fPD = 1.728 MHz). Open loop modulation is
supported.
3.4 Power Supply
An integrated bandgap-stabilized voltage regulator for use with an external low-cost PNP
transistor is implemented. Multiple power-down and current saving modes are provided.
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4572I–DECT–07/05
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