AX5031_16 Datasheet, PDF (13/22 Pages) ON Semiconductor – Advanced Multi-channel Single Chip UHF Transmitter

AX5031
Modulator
Depending on the transmitter settings the modulator
generates various inputs for the PA:
Table 12.
Modulation
ASK
FSK/MSK/GFSK
PSK
Bit = 0
PA off
Df = −f_deviation
DF = 0°
Bit = 1
PA on
Df = +f_deviation
DF = 180°
Main Lobe Bandwidth
BW = BITRATE
BW = (1 + h) ⋅BITRATE
BW = BITRATE
Max. Bitrate
2000 kBit/s
350 kBit/s
2000 kBit/s
h
ASK
FSK
MSK
= modulation index. It is the ratio of the
deviation compared to the bit−rate;
f_deviation = 0.5⋅h⋅BITRATE
= amplitude shift keying
= frequency shift keying
= minimum shift keying; MSK is a special case
of FSK, where h = 0.5, and therefore
f_deviation = 0.25⋅BITRATE; the advantage of
MSK over FSK is that it can be demodulated
more robustly.
PSK = phase shift keying
OQPSK = offset quadrature shift keying. The AX5031
supports OQPSK. However, unless
compatibility to an existing system is required,
MSK should be preferred.
4−FSK = four frequencies are used to transmit two bits
simultaneously during each symbol
Table 13.
Modulation
4−FSK
Symbol = 00
Df = −3⋅f_deviation
Symbol = 01
Df = −f_deviation
Symbol = 10
Df = +f_deviation
Symbol = 11
Df = +3⋅f_deviation
Max. Bitrate
400 kBit/s
All modulation schemes are binary.
PWRMODE Register
The PWRMODE register controls, which parts of the chip are operating.
Table 14. PWRMODE REGISTER
PWRMODE Register
Name
0000
POWERDOWN
0100
VREGON
0101
1100
STANDBY
SYNTHTX
1101
FULLTX
Description
All digital and analog functions, except the register file, are disabled. The
core supply voltage is reduced to conserve leakage power. SPI registers
are still accessible, but at a slower speed. FIFO access is possible.
All digital and analog functions, except the register file, are disabled. The
core voltage, however is at its nominal value for operation, and all SPI
registers are accessible at the maximum speed.
The crystal oscillator is powered on; the transmitter is off.
The synthesizer is running on the transmit frequency. The transmitter is still
off. This mode is used to let the synthesizer settle on the correct frequency
for transmit.
Synthesizer and transmitter are running. Do not switch into this mode
before the synthesizer has completely settled on the transmit frequency (in
SYNTHTX mode), otherwise spurious spectral transmissions will occur.
Typical Idd
0.25 mA
140 mA
500 mA
10 mA
11 − 45 mA
Table 15. A TYPICAL PWRMODE SEQUENCE FOR A TRANSMIT SESSION
Step
PWRMODE
Remarks
1
POWERDOWN
2
STANDBY
The settling time is dominated by the crystal used, typical value 3 ms.
4
SYNTHTX
The synthesizer settling time is 5 – 50 ms depending on settings, see section AC Characteristics
3
FULLTX
Data transmission
4
POWERDOWN
www.onsemi.com
13