TH72036 Datasheet, PDF (6/16 Pages) Melexis Microelectronic Systems – 868/915MHz FSK/ASK Transmitter

TH72036
868/915MHz
FSK/ASK Transmitter
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 EN is pulled-down
internally. This guarantees that the whole circuit
is shut down if this pin is left floating.
EN
Mode
Description
0
TX standby
TX disabled
1
TX active
TX / CKOUT
CKOUT active
enabled
2.9 Clock Output
The clock output CKOUT is CMOS-compatible and can be used to drive a microcontroller. The frequency of
the clock can be selected by the clock divider control signal CKDIV, according to the following table.
A capacitor at pin CKOUT can be used to control the clock voltage swing and the RF spurious emission.
PRELIMINARY CKDIV
0
1
Clock divider ratio
8
32
Clock frequency / f_c=868.3MHz
3.39MHz
848kHz
2.10 Timing Diagrams
After enabling the transmitter by the EN 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 or ASK modulated.
high
high
EN
EN
low
low
high
LOCK
low
high
LOCK
low
high
FSKDTA
low
high
PSEL
low
RF carrier
3901072036
Rev. 005
t
t _on
t _on
Fig. 5: Timing diagrams for FSK and ASK modulation
Page 6 of 16
t
Data Sheet
June/07