Micrel, Inc.

MICRF112

February 2013

11

M9999-020713

Functional Diagram

Figure 1. Functional Block Diagram MICRF112 10 Pin ASK/FSK Version

Functional Description

Figure 1 shows a functional block diagram of the

MICRF112 transmitter. The MICRF112 can be best

described as a phase-locked transmitter. The system

can be partitioned into six functional blocks: crystal

oscillator, PLL×32, power

amplifier, enable control,

undervoltage detect, and open-drain switch for FSK

operation.

Crystal Oscillator

The reference oscillator is a crystal-based Pierce

configuration. It is designed to accept crystals with

frequencies from 9.375MHz to 14.0625MHz.

Crystal Oscillator Parameters for ASK Operation

Figure

2

shows

a

reference

oscillator

circuit

configuration for ASK operation. The reference oscillator

can drive crystals with an ESR range from 20

Ω to 300Ω.

When the ESR of the crystal is at 20

Ω, the crystal

parameter limits are:

ESR

20

Ω

2 to 10pF

10 to 40fF

Figure 2. Reference Oscillator ASK Operation

When the ESR of the

crystal is at 300Ω, the crystal

parameter limits are:

ESR

300

Ω

2 to 5pF

10 to 40fF

10 to 30pF