EVB72015
433MHz FSK/ASK Transmitter
Evaluation Board Description
2.8 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
Mode
Description
TX disabled
TX enable
0
1
TX standby
TX active
2.9 Timing Diagrams
After enabling the transmitter by the ENTX signal, the power amplifier remains inactive for the time ton, the
transmitter start-up time. The crystal oscillator starts oscillation and the PLL locks to the desired output fre-
quency within the time duration ton. After successful PLL lock, the LOCK signal turns on the power amplifier,
and then the RF carrier can be FSK or ASK modulated.
high
ENTX
low
high
ENTX
low
high
high
LOCK
LOCK
low
low
high
high
FSKDTA
ASKDTA
low
low
RF carrier
t
t
t
t
on
on
Fig. 5: Timing diagrams for FSK and ASK modulation
For more detailed information, please refer to the latest TH72015 data sheet revision.
39012 72015 01
Rev. 007
Page 6 of 14
EVB Description
June/07
MELEXIS [ Melexis Microelectronic Systems ]
