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CT2-RX/TX IC
U2760B
Description
The IC for digital cordless telephone application is
fabricated using TEMIC’s most advanced UHF process.
It covers the CT2 band (864 MHz to 868 MHz) as well as
the CT2 Plus band (up to 952 MHz). The RX/TX circuit
provides the down conversion to the data stream and the
up conversion from the first IF. In conjunction with
TEMIC’s RF front end, Twin PLL, I/Q modulator and
AMDs CT2 PhoXTM controller AM 79C4xx a complete
CT2 IC kit is available.
Electrostatic sensitive device.
Observe precautions for handling.
Features
D Low supply voltage 2.9 V typical (min. 2.7 V)
D Provides down conversion to the data stream,
up conversion from the first IF
vD Integrated UHF and VHF VCOs
D Low noise figure of RX path (NF 10 dB)
D RX and TX power down
D First IF filter used for transmit as well receive mode
D Temperature compensated logarithmic Receiver
Signal Strength Indicator (RSSI) with a 75 dB
dynamic range
D Low power consumption in RX and TX mode
(<20 mA typ.)
D SSO28 plastic package
Benefits
D Low power consumption results in extended talk time
D Few external components and very small package
save space
Block Diagram (Simplified Schematic)
RX enable
MX1 in
15
21
VCO1 ref
VCO1 tank
VCO1 out
MX4 outn
MX4 outp
TX enable
7
6
5
22
23
24
MX1/3 MX1/3 MX2/4 MX2/4
outp outn in nin
26 25 1 2
MX2 out
28
LIMIT in VCC
4 20
GND
19
MX1
MX2
LIMIT
RSSI
27 RSSI out
VCO1
MX4
9
VCC
vco/lf
8
GND
vco/lf
VCO2
DEMOD 10 pF 11 QUAD
MX3
3
MX3 in
17 18 16
VCO2 VCO2 VCO2
ref tank out
12
100kW13
COMP
100kW
10 14
RXdata
94 9532
DEMOD out
COMP in
COMP cap
Figure 1.
Rev. A3, 05-Oct-98
1 (14)

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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
WThe 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

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U2760B
Pin Description
MX2/4in 1
MX2/4nin 2
MX3in 3
LIMITin 4
VCO1out 5
VCO1tank 6
VCO1ref 7
GNDvco/If 8
VCCvco/If 9
RXdata 10
QUAD 11
DEMODout 12
COMPin 13
COMPcab 14
Figure 2. Pinning
28 MX2out
27 RSSIout
26 MX1/3outp
25 MX1/3outn
24 TXenable
23 MX4outp
22 MX4outn
21 MX1in
20 VCC
19 GND
18 VCO2tank
17 VCO2ref
16 VCO2out
15 RXenable
Pin Symbol
Function
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ1 MX2/4in Mixer2/ Mixer4 input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ2 MX2/4nin Mixer2/ Mixer4 ref. input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ3 MX3in Mixer3 input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ4 LIMITin Limiter/RSSI input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ5 VCO1out VCO1 output (to PLL)
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ6 VCO1tank VCO1 resonator
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ7 VCO1ref VCO1 resonator, to be blocked
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ8 GNDvco/lf Ground VCO, low frequency
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁparts
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ9 VCCvco/lf Power supply VCO/LF parts
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ10 RXdata RX data output
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ11 QUAD Quadrature filter
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ12 DEMODout Demodulator output
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ13 COMPin Comparator input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ14 COMPcap Comparator blocking capacitor
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ15 RXenable RX enable
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ16 VCO2out VCO2 output (to PLL)
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ17 VCO2ref VCO2 resonator, to be blocked
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ18 VCO2tank VCO2 resonator
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ19 GND Ground
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ20 VCC Power supply voltage
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ21 MX1in Mixer1 input
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ22 MX4outn Mixer 4 output n
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ23 MX4outp Mixer 4 output p
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ24 TXenable TX enable
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ25 MX1/3outn Mixer1/ Mixer3 output n
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ26 MX1/3outp Mixer1/ Mixer3 output p
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ27 RSSIout Signal strength output
ÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁÁ28 MX2out Mixer2 output
Rev. A3, 05-Oct-98
3 (14)