AX8052F131

www.onsemi.com

23

Modulator

Depending on the transmitter settings the modulator generates various inputs for the PA:

Table 18.

Modulation

Bit = 0

Bit = 1

Main Lobe Bandwidth

Max. Bitrate

ASK

PA off

PA on

BW = BITRATE

2000 kBit/s

FSK / MSK / GFSK

BW = (1 + h) ⋅BITRATE

350 kBit/s

PSK

DF = 0°

DF = 180°

BW = BITRATE

2000 kBit/s

h

= modulation index. It is the ratio of the

deviation compared to the bit−rate;

demodulate signals with h < 32.

ASK

= amplitude shift keying

FSK

= frequency shift keying

MSK

= minimum shift keying; MSK is a special case

of FSK, where h = 0.5, and therefore

MSK over FSK is that it can be demodulated

more robustly.

PSK

= phase shift keying

OQPSK = offset quadrature shift keying. The

AX8052F131 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

All modulation schemes are binary.

Table 19.

Modulation

Symbol = 00

Symbol = 01

Symbol = 10

Symbol = 11

Max. Bitrate

4−FSK

400 kBit/s

PWRMODE Register

The AX8052F131 transmitter features its own

independent power management, independent from the

microcontroller. While the microcontroller power mode is

controlled

through

the

PCON

register,

the

AX5031_PWRMODE register controls which parts of the

transmitter are operating.

Table 20. PWRMODE REGISTER

AX5031_PWRMODE

Register

Name

Description

0000

POWERDOWN

All digital and analog transmitter functions, except the register file, are disabled.

VREG is reduced to conserve leakage power. The registers are still accessible.

0100

VREGON

All digital and analog transmitter functions, except the register file, are disabled.

VREG, however is at its nominal value for operation, and all registers are accessible.

0101

STANDBY

The crystal oscillator is powered on; the transmitter is off.

1100

SYNTHTX

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.

1101

FULLTX

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.

Table 21. A TYPICAL AX5031_PWRMODE SEQUENCE FOR A TRANSMIT SESSION

Step

PWRMODE [3:0]

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