TH72031 Datasheet, PDF (6/20 Pages) Melexis Microelectronic Systems – 868/915MHz FSK Transmitter

TH72031
868/915MHz
FSK Transmitter
2.7 Mode Control Logic
The mode control logic allows two different
modes of operation as listed in the following
table. The mode control pin ENTX is pulled-
down internally. This guarantees that the whole
circuit is shut down if this pin is left floating.
ENTX
0
1
Mode
TX standby
TX active
Description
TX disabled
TX enable
2.8 Timing Diagrams
After enabling the transmitter by the ENTX signal, the power amplifier remains inactive for the time t_on, the
transmitter start-up time. The crystal oscillator starts oscillation and the PLL locks to the desired output fre-
quency within the time duration t_on. After successful PLL lock, the LOCK signal turns on the power amplifier,
and then the RF carrier can be FSK modulated.
high
ENTX
low
high
LOCK
low
high
FSKDTA
low
RF carrier
t
t _on
Fig. 5: Timing diagram for FSK modulation
3901072031
Rev. 008
Page 6 of 20
Data Sheet
June/07