4

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

low (1 µs fall time).

The maximum time required to switch from the sleep mode to either

start-up of the transmitter oscillator.

3

4

5

6

7

9

11

12

13

14

15

16

17

19

Tr a n s m i t t e r P i n O u t

RF I O

8

2

10

20

1

18

NC

NC

NC

NC

NC

NC

NC

NC

TX M O D

N C

NC

NC

G ND1

VC C 1

G ND2

VC C 2

G ND3

CNT R L 0

CNT R L 1

S M - 20L P ackag e D r aw i n g

0. 08"

( 2 . 03)

0. 125"

(3 . 2 0 )

0. 02"

(0 . 5 1 )

0. 04"

(1 . 0 2 )

0. 13"

( 3 . 30)

0. 43"

( 10. 9)

0. 38"

( 9 . 65)

0. 075"

(1 . 9 0 )

0. 000

.0 7 7 5

.1 0 25

.1 1 7 5

.1 5 7 5

.1 9 7 5

.23 7 5

.27 7 5

.3 1 7 5

.3 5 7 5

.3 8 25

.4 6 0 0

D i m e ns i o ns i n i n c hes

S M - 20 L P C B P a d L a y o u t