MICRF112 datasheet(26/46 Pages) MICROCHIP

Part #	MICRF112

Description	The MICRF112 is a high-performance, easy-to-use, true “Data-In, RF-Out”, ASK/FSK, Phase-Locked Loop (PLL)- based, transmitter IC for applications in the 300 MHz to 450 MHz frequency range.

PDF	46 Pages

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Manufacturer	MICROCHIP [Microchip Technology]

Direct Link	http://www.microchip.com

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26 / 46 page

MICRF112

Functional Description

Data Sheet

DS70005554A - 26

Figure 6-3. Reference Oscillator FSK Operation

FSK

PLL×32

The function of PLL×32 is to provide a stable carrier frequency for transmission. It is a “divided by 32”

phase-locked oscillator.

Power Amplifier

The power amplifier serves two purposes: to buffer the VCO from external elements and to amplify

the phase-locked signal. The power amplifier can produce +10 dBm at 3V (typical).

Enable Control

The enable control gates the ASK data. It only allows transmission when Lock, Amplitude and

Undervoltage Detect conditions are valid.

Undervoltage Detect

The undervoltage detect block senses operating voltage. If the operating voltage falls below 1.6V, the

undervoltage detect block sends a signal to the enable control block to disable the PA.

Open-Drain Switch

The open-drain switch is used for FSK operation. FSK data is fed into the FSK pin. The FSK pin is

connected to the gate of the open-drain switch. The open collector is connected to the XTAL_MOD

pin. In Figure 6-3, a capacitor is shown connected from the XTAL_MOD pin to XTLOUT. When the FSK

pin goes high, the capacitor between XTAL_MOD and XTLOUT pulls the frequency of REFOSC low.

MICRF112 Datasheet(PDF) 26 Page - Microchip Technology