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TR3003-070105

Pin

Name

Description

15

PWIDTH

A ±5% resistor value is recommended. When this pin is connected to Vcc through a 1 M resistor, the RF amplifiers operate

at a nominal 50%-50% duty cycle, facilitating high data rate operation. In this case, the RF amplifier ON times are con-

trolled by the PRATE resistor as described above. It is important to keep the total capacitance between ground, Vcc and

this node to less than 5 pF to maintain stability. When using the high data rate operation with the sleep mode, connect the

1 M resistor between this pin and CNTRL1 (Pin 17), so this pin is low in the sleep mode.

16

VCC2

VCC2 is the positive supply voltage pin for the receiver RF section and transmitter oscillator. Pin 16 must be bypassed with

an RF capacitor, and must also be bypassed with a 1 to 10 µF tantalum or electrolytic capacitor. See the ASH Transceiver

Designer’s Guide for additional information.

17

CNTRL1

CNTRL1 and CNTRL0 select the receive and transmit modes. CNTRL1 and CNTRL0 both high place the unit in the

receive mode. CNTRL1 high and CNTRL0 low place the unit in the ASK transmit mode. CNTRL1 low and CNTRL0 high

place the unit in the OOK transmit mode. CNTRL1 and CNTRL0 both low place the unit in the power-down (sleep) mode.

CNTRL1 is a high-impedance input (CMOS compatible). An input voltage of 0 to 300 mV is interpreted as a logic low. An

input voltage of Vcc - 300 mV or greater is interpreted as a logic high. An input voltage greater than Vcc + 200 mV should

not be applied to this pin. A logic high requires a maximum source current of 40 µA. A logic low requires a maximum sink

current of 25 µA (1 µA in sleep mode). This pin must be held at a logic level; it cannot be left unconnected.

18

CNTRL0

CNTRL0 is used with CNTRL1 to control the receive and transmit modes of the transceiver. CNTRL0 is a high-impedance

input (CMOS compatible). An input voltage of 0 to 300 mV is interpreted as a logic low. An input voltage of Vcc - 300 mV or

greater is interpreted as a logic high. An input voltage greater than Vcc + 200 mV should not be applied to this pin. A logic

high requires a maximum source current of 40 µA. A logic low requires a maximum sink current of 25 µA (1 µA in sleep

mode). This pin must be held at a logic level; it cannot be left unconnected.

19

GND3

GND3 is an IC ground pin. It should be connected to GND1 by a short, low inductance trace.

20

RFIO

RFIO is the RF input/output pin. This pin is connected directly to the SAW filter transducer. Antennas presenting an imped-

ance in the range of 35 to 72 ohms resistive can be satisfactorily matched to this pin with a series matching coil and a

shunt matching/ESD protection coil. Other antenna impedances can be matched using two or three components. For

some impedances, two inductors and a capacitor will be required. A DC path from RFIO to ground is required for ESD pro-

tection.

0.000

.0775

.1025

.1175

.1575

.1975

.2375

.2775

.3175

.3575

.3825

.4600

Dimensions in inches

SM-20L PCB Pad Layout