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U3770M Datasheet(PDF) 2 Page - TEMIC Semiconductors

No. de Pieza. U3770M
Descripción  CT2 I/Q Modulator and Clock Circuitry
Descarga  5 Pages
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Fabricante  TEMIC [TEMIC Semiconductors]
Página de inicio  http://www.temic.de
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U3770M Datasheet(HTML) 2 Page - TEMIC Semiconductors

   
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U3770M
MATRA MHS
Rev. A2, 03-Dec-97
2 (5)
Functional Description
U3770M has been designed to reduce power consumption
and cost of CT2 devices. An innovative CMOS I,Q modu-
lator with an extremely low current provides all the
advantages of I,Q modulation:
No requirement for FM deviation tuning
Eliminates the Gaussian filter
Simplifies the power ramping control
The modulated output carrier can be programmed to be
0.8 MHz or 1.6 MHz by the PROG control pin.
The typical supply voltage is 3 V @ 4 mA.
To reduce overall system cost, an internal PLL generates
a 18.432 MHz clock signal from the system 12.8 MHz
reference oscillator. This way, only one crystal oscillator
is needed in the complete CT2 device.
Internally, the 12.8 MHz reference signal is fed into a
shaping amplifier and then into two logic dividers, to gen-
erate a 512 kHz and a programmable 3.2 or 6.4 MHz
clock. This clock is divided by 4 by two D flip-flops. The
flip-flop outputs drive the four analog switches in quadra-
ture. A pair of analog switches make a local oscillator
(LO) suppression mixer. By summing the other pair out-
puts, we obtain both LO and sideband suppression, of
more than –26 dBc.
The 512 kHz clock drives a frequency synthesizer. The
VCO runs at a fixed frequency of 18.432 MHz. The VCO
control voltage (LF pin) controls the VCO frequency.
Pin Description
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
95 9930
DNC
FRef in
VDD
DGND
QB
Q
IB
I
DNC
DNC
CLKout
AGND
PROG
LF
TST
MODout
Figure 2. Pinning
Pin
Symbol
Function
2
FRef in
External 12.8 MHz reference
frequency input
3
VDD
Supply voltage
4
DGND
Digital ground
5
QBin
Analog switches input
6
Qin
Analog switches input
7
IBin
Analog switches input
8
Iin
Analog switches input
9
MODout
Modulator output signal
10
TST
Test input, must be connected to
GND (only factory use)
11
LF
PLL loop filter
12
PROG
PROG = 0, 1.6 MHz mode
PROG = 1, 0.8 MHz mode
13
AGND
Analog ground
14
CLKout
Digital CMOS clock output
18.432 MHz
1, 15,
16
DNC
Do not connect


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