The transmitter RF output power is proportional to the input current
to the TXMOD pin. A series resistor is used to adjust the peak trans-
mitter output power. 0 dBm of output power requires about 250 µA
of input current.
Transmitter Mode Control
The three transmitter operating modes – transmit ASK, transmit
OOK, and power-down (sleep), are controlled by the Modulation &
Bias Control function, and are selected with the CNTRL1 and
CNTRL0 control pins. Setting CNTRL1 high and CNTRL0 low place
the unit in the ASK transmit mode. Setting CNTRL1 low and
CNTRL0 high place the unit in the OOK transmit mode. Setting
CNTRL1 and CNTRL0 both low place the unit in the power-down
mode. (Note that the resistor driving TXMOD must also be low in the
power-down mode to minimize power-down current.) CNTRL1 and
CNTRL0 are CMOS compatible inputs. These inputs must be held
at a logic level; they cannot be left unconnected.
Turn-On Timing
The maximum time required for either the OOK or ASK transmitter
mode to become operational is 5 ms after the supply voltage
reaches 2.2 Vdc. The total turn-on time to stable transmitter opera-
tion for a 10 ms power supply rise time is 15 ms.
Sleep and Wake-Up Timing
The maximum transition time from either transmit mode to the sleep
mode (t
TOS
and t
TAS
) is 15 µs after CNTRL1 and CNTRL0 are both
low (1 µs fall time).
The maximum time required to switch from the sleep mode to either
transmit mode (t
STO
and t
STA
) is 21 µs. Most of this time is due to the
start-up of the transmitter oscillator.
S M -2 0 L P a c k a g e D r a w in g
0 .3 8 "
(9 .6 5 )
0 .0 8 "
(2 .0 3 )
0 .1 2 5 "
(3 .2 0 )
T r a n s m itte r P in O u t
G N D 1
0 .0 2 "
(0 .5 1 )
R F IO
1
2 0
1 9
2
3
4
5
6
7
8
9
1 0
1 1
N C
1 8
1 7
1 6
1 5
1 4
1 3
1 2
G N D 3
C N T R L 0
C N T R L 1
V C C 2
N C
N C
N C
N C
V C C 1
N C
0 .4 3 "
(1 0 .9 )
0 .0 4 "
(1 .0 2 )
N C
N C
N C
0 .0 7 5 "
(1 .9 0 )
0 .1 3 "
(3 .3 0 )
N C
T X M O D
N C
G N D 2
.1 7 2 5
.1 9 7 5
.2 1 2 5
.4 6 0 0
.2 3 7 5
.3 8 2 5
.3 5 7 5
.3 1 7 5
.2 7 7 5
.2 3 7 5
.1 9 7 5
.1 5 7 5
.1 1 7 5
.1 0 2 5
.0 7 7 5
.1 4 0
0 .0 0 0
.2 7 0
.4 1 0
0 .0 0 0
D im e n s io n s in in c h e s
S M -2 0 L P C B P a d L a y o u t
4
RFM [ RF MONOLITHICS, INC ]
