AS3901 Просмотр технического описания (PDF) - austriamicrosystems AG
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AS3901 Datasheet PDF : 18 Pages
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ISM 433/315 MHz FSK/ASK Transmitter – Data Sheet
AS3901
1 Functional Description
The AS3901 consists of a reference XTAL oscillator, a single channel RF- synthesizer,
an I/Q based asynchronous continuos phase FSK modulator, a driving amplifier and a
µC interface, including µC clock divider, and a power management circuitry.
VDD
f =433.920 MHz
XTAL1
8
433
9
VDDRF
10
ANT2
11
ANT1
12
GNDRF
13
NRES
14
Driving
Amplifier.
Synthesizer
VCO
Loop-
Filter
Divider
32:1
Phase
Detector
SSB signal
generation
AS3901
XTAL
Oscillator
Clock
µC Interface +
Power up/down
XTAL2
7
VDD
6
13.560 MHz
XTAL
GND
5
TX
4
DATA
3
CLK
2
STDBY
1
Figure 1:
Block diagram of the AS3901.
1.1 RF Synthesizer
The RF synthesizer is a fully integrated single channel device with internal loop filter,
generating the 433 MHz or 315 MHz transmit carrier frequency fRF by a fix, 32 times,
multiplication of the reference XTAL frequency fXTAL.
1.2 Microprocessor Clock
The microprocesor clock frequency fCLK is generated by dividing the XTAL frequency fXTAL
by 3 or 4, dependent on the 433/315 MHz selection pin to keep the µC clock frequency
fCLK almost constant for European and US applications.
1.3 Modulation
The FSK modulator is an I/Q modulator based continuos phase FSK modulator. The
modulating NRZ data may be in the range of 0 up to 32 kbit/s. The FSK frequency
deviation ∆f is ≈16 kHz, independent of the data rate. It is also kept almost constant for
both transmit frequency bands by selecting proper frequency deviation multiplication
factors of the XTAL reference frequency by the 433/315 MHz selection pin.
The processing clock of the data source can be different from the AS3901 reference
XTAL or µC clock fCLK and no data synchronization of the FSK modulator is required.
Rev. 6, August 2000
Page 4 of 18
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