U2760B Datasheet, PDF (2/14 Pages) TEMIC Semiconductors – CT2-RX/TX IC

U2760B
Ordering Information
Extended Type Number
U2760B-AFS
U2760B-AFS G3
Package
SSO28
SSO28
Remarks
Rail, MOQ 600pcs.
Tape + reel, MOQ 4000 pcs.
Functional Description
MX1
Mixer 1 converts the RF signal to the first IF. It has a high
impedance, unsymmetrical input and a symmetrical open
collector output.
MX2
The second mixer provides the down conversion to the
second IF. An external SAW filter is placed at its input to
provide rejection of the image frequency and spurious
signals that went through the RF filtering.
LIMITER / RSSI
This block contains a high gain (100 dB) amplifier,
providing a limited signal at the second IF frequency for
the demodulation, as well as a signal strength indicator
providing an output voltage proportional to the input
power.
Demod
The quadrature demodulator in the receiving path
contains an internal 10 pF quadrature capacitor to couple
the IF signal to the external Tank providing the 90 degree
phase shift. An external bit slicer reshapes the bits, a
sample and hold circuit maintains the average DC value
at the demodulator when switching the signal between
transmission and reception.
COMP
W The comparator circuit with 100 k input resistor and
external input biasing has a 10 mV hysteresis. It is
designed to square up the demodulated data signal.
MX3
The third mixer converts the 800 kHz signal coming from
the modulator circuit to the IF frequency. It has a high
impedance, unsymmetrical input and a symmetrical open
collector output.
MX4
This mixer is designed for the up conversion of the RF
frequency. It has a high impedance, unsymmetrical input
and a symmetrical open collector output. The image
rejection is obtained by external RF filtering.
The same first IF filter is used for the transmit path and
the receive path. In the transmit path, this filter is
supposed to eliminate the mixing products from MX3, in
particular, the harmonics of the IF frequency.
VCO1
The UHF VCO covers the frequency band up to
700 MHz. For external VCO application this circuit can
be used as a buffer stage.
VCO2
This VCO covers a frequency band up to 400 MHz.
2 (14)
Rev. A3, 05-Oct-98