RFPIC12F675 datasheet(56/136 Pages) MICROCHIP

Part #	RFPIC12F675

Description	20-Pin FLASH-Based 8-Bit CMOS Microcontroller with UHF ASK/FSK Transmitter

PDF	136 Pages

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Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

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56 / 136 page

rfPIC12F675

DS70091A-page 54

Preliminary

 2003 Microchip Technology Inc.

9.9

Digital Control Signals

The mode control logic pin RFEN controls the

operation of the transmitter. When RFEN goes high,

the crystal oscillator starts up. The voltage on the LF

pin ramps up proportionally to the RF frequency. The

PLL can lock onto the frequency faster than the start-

ing up crystal can stabilize. When the LF pin reaches

0.8V, the RF frequency is close to locked on the crys-

tal frequency. This initiates a 150 microsecond delay

to ensure that the PLL settles. After the delay, the PS

bias current and power amplifier are enabled to start

transmitting when DATA

ASK goes high.

When RFEN is low, the transmitter goes into a very

low power Standby mode. The power amplifier is

disabled and the crystal oscillator stops. The RFEN

pin has an internal pull-down resistor.

9.10

Low Voltage Output Disable

The rfPIC12F675 transmitter has a built in low voltage

disable centered at about 1.85V. If the supply voltage

drops below this voltage the power amplifier is

disabled to prevent uncontrolled transmissions.

RFPIC12F675 Datasheet(PDF) 56 Page - Microchip Technology