41594B datasheet(299/372 Pages) MICROCHIP

299 / 372 page

 2011-2012 Microchip Technology Inc.

Preliminary

DS41594B-page 299

PIC12LF1840T48A

28.0 RF TRANSMITTER

The RF transmitter is a fully integrated transmitter,

capable of Frequency-Shift Keying (FSK) and On-Off

Keying (OOK) modulation of an input data stream. The

transmitter is capable of operating in Preset or

Advanced mode. The Preset mode configures the RF

transmitter in one or two fixed configurations.

28.1

Mode Selection

Two modes of operation are supported: Preset and

Advanced. Preset mode allows operation in one of two

preconfigured modes. Advanced mode allows full con-

figuration of all features of the transmitter. Mode selec-

tion is made by applying a logical ‘1’ or ‘0’ on the CTRL

pin during power-up, followed by a clock signal on the

DATA pin if Advanced mode is required.

FIGURE 28-1:

MODE SELECTION

28.1.1

PRESET MODE

In Preset mode, the transmitter is configured according

to Table 28-1. One of the two configuration modes can

be selected by changing the logical state of the CTRL

pin at power-up. The timing of a typical transmit opera-

tion in Preset mode is shown in Figure 28-2. A rising

edge on the DATA pin activates the transmitter. DATA

must be held high for the start-up time, TWAKE, while

the transmitter transitions out of Sleep mode. Signals

on the DATA pin, after the start-up time has elapsed,

are then transmitted.

The transition back to Sleep mode is managed auto-

matically. In 868 MHz FSK mode, the transmitter

returns to Sleep mode after 2 ms of inactivity on the

DATA line. In 434 MHz OOK mode, the transmitter

returns to Sleep after 20 ms of inactivity.

TABLE 28-1:

PRESET MODE

CONFIGURATIONS

FIGURE 28-2:

TRANSMITTER TIMING IN

PRESET MODE

Circuit Start-up

Wait t

START

Check

CTRL Pin

Preset

434 MHz OOK Tx

Preset

868 MHz FSK Tx

Advanced Mode

User-defined

Configuration

Clock Signal

Logic ‘1’

Logic ‘0’

CTRL

Configuration

OOK 433.92 MHz, 10 dBm

FSK 868.3 MHz, FDEV = 20 kHz, 10 dBm

Note 1: While the logic level of CTRL pin during

TSTART does not have any effect on the

device operation, the pin should not be

connected to VDD through an impedance

lower than 20 kΩ or higher than 1 MΩ.

WAKE

OFFT

Data

RF Out

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